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On Sun, May 24, 2020 at 08:42 PM, Glen Christensen wrote:
I thought that the less load would be less consumption of power.
Why would a clogged up system or one with more restriction use less power? I find this very interesting.
The work (in a physics sense) that a fan does is move air.? The more air moved, the more work done, the more power required.? A low-restriction system moves a lot a air, and thus does a lot of work and draws a lot of power.? With some restrictions, less air is moved, less work is done, less power needed.?? Imagine you are draining your swimming pool with a 5 gallon bucket.? If you can just throw the water over the side, nothing limits how fast you can work, except available power.? But suppose you are pouring the buckets down your sink drain.? It restricts the rate of work you can do, and thus limits the power drawn from your arms.
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Another way to think is that fan is spinning in still air and thus doing no work.
Imran
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On May 25, 2020, at 2:23 AM, mark thomas <murkyd@...> wrote: ?On Sun, May 24, 2020 at 08:42 PM, Glen Christensen wrote:
I thought that the less load would be less consumption of power.
Why would a clogged up system or one with more restriction use less power? I find this very interesting.
The work (in a physics sense) that a fan does is move air.? The more air moved, the more work done, the more power required.? A low-restriction system moves a lot a air, and thus does a lot of work and draws a lot of power.? With some restrictions, less air is moved, less work is done, less power needed.?? Imagine you are draining your swimming pool with a 5 gallon bucket.? If you can just throw the water over the side, nothing limits how fast you can work, except available power.? But suppose you are pouring the buckets down your sink drain.? It restricts the rate of work you can do, and thus limits the power drawn from your arms.
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Brian, the point is doing the work creates heat too.? Take a milling machine.? The motor has inefficiency, heat. The motor moves things in the mill, some friction some more heat.? Then the cutter removes metal, more heat. The coolant cools
the metal warming the coolant. 100% of the energy in ends up as either potential energy like raising a hoist, or heat. With lighting the energy either turns into light which shines on objects and heats them or it is wasted in the LED driver etc.
?
You all are missing the point that a lot of the hp/watts is actually consumed doing the “work”, whether it’s sawing the wood, jointing, planing, sanding, lighting or even compressing air. It takes force to do most of these things (not lighting
of course), and the force of the blade cutting through the wood is a large percentage of the watts consumed. Yes, there is always a heat load, but it’s not anywhere close to 100% of consumed power…. even here in AZ where it will be 111? later this week.
Brian Lamb
blamb11@...
?
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From: [email protected] < [email protected]>
On Behalf Of Brian Lamb
Sent: Saturday, May 23, 2020 7:36 AM
To: [email protected]
Subject: Re: [FOG] Building a closet for dust collector
?
You all are missing the point that a lot of the hp/watts is actually consumed doing the “work”, whether it’s sawing the wood, jointing, planing, sanding, lighting or even compressing air. It takes force to do most of these things (not lighting
of course), and the force of the blade cutting through the wood is a large percentage of the watts consumed. Yes, there is always a heat load, but it’s not anywhere close to 100% of consumed power…. even here in AZ where it will be 111? later this week.
?
?
I think perhaps the issue then is the usual workload of a typical shop. Although in an it system things are, I imagine, a bit more stable in terms of draw and power use,
that is not the case for most shops not in a factory environment. We tend to turn on and off equipment and not be steadily throwing plank after plank in rapid succession thorough a saw at max force leading to an actual nameplate type draw. Whereas computer
fans are typically more blunt force objects running at max 100% of the time to account for a potentially catastrophic consequence of failing to control heat in a limited space and the consequences of those failures. And so, I may allow for a total heat release
into your shop for the sake of argument, but even then, the draw is variable and subsequently the heat release. If the OP is concerned about utilizing a motor and dealing with the heat for 100% utilization, he is probably 1) not using the right equipment as
Felder doesn’t spec the duty as 100%, and 2) in the wrong forum and needs to be talking to factory owners.
But in more real world situations, we don’t use 100% draw even when we are using machines most of the time, turn them off between runs, have leaks under a doors, windows
to radiate out, poor insulation to not contain heat or cold, and a myriad of other issues. Sure, running motors will increase heat but it’s not a 1:1 in any of our shops, and especially not at nameplate levels.
I think you just said mostly what I did – that the energy turns into heat, just not entirely in the motor itself.?
?
8KW of electricity into a room turns into 27,000 of BTU in that room, either directly or indirectly, unless that motor is driving a shaft through a wall where some of that energy is converted into heat somewhere else. That 8KW of heat may
not stay in the room due to diffusion through the room walls and ceiling, but it’s put into the room, no if’s, and’s, or but’s, just as if you had an 8KW electric resistance heater.
?
Energy is not returned to the environment on the return leg – the neutral wire in a single phase 120v world, or the other hot legs in a 240v or 3-phase world. If the energy is not needed for work output or system inefficiency losses it
is not drawn in the first place; e.g. a 5HP/3KW motor has a free-running power consumption value of maybe 1KW, and that power consumption increases when the motor is asked to do work. Only when the motor is fully loaded does it draw 3KW of power. Yes there
is voltage drop on the electrical service wiring and yes there is heat generated from that lost energy, but that’s a different problem in a different room. Power distribution is sized to deliver nominal voltage at the end point, factoring in losses in distribution.
?
RE designing HVAC based on electrical load – yes, this is exactly how it’s done. My day job is in IT, part of which includes managing a datacenter and it’s power and cooling. Cooling load is absolutely sized based on power draw of computing
equipment as well as the expected environmental factors. ??
?
Small spaces like workshops – small closed systems – will show the temperature rise of power consumption more quickly than a larger system which has a lot more thermal sinking capability.
?
I agree it’s complicated, and I’m glad nothing is simple on the Felder forum, which I’m new to. There are few things in life that can truly be expressed simply.? Learning stuff – the reason I joined the group – happens when the complexity
is welcomed.??
?
No. While you may be correct that the differences between potential energy and kinetic reach equilibrium through heat transfer, it’s not so clear cut as the statement that an 8kw input to a motor yields 8kw of heat within a workshop. Within
systems there are many components, heat sinks, and losses. So for example, the spinning motor creates heat in bearings through friction, the blade creates heat through friction in the wood and drag through air, some energy is passed through entirely in the
electrical supply and leaves the system and recovers its potential in a ground, some energy is absorbed through wood fibers/saw dust and heat sinked. Heat is lost through inefficient insulation, air drafts, radiation through windows etc. Some energy is released
slowly and muddies the results like the specific heat of cast iron and sawdust. All causes, yes, 8kw input leads to 8kw of heat. But the closed system needs to be very large which simply is out of line with a real world workshop. I don’t know much about sizing
hvac but I don’t think this is the way to do it.
Nothing is simple on a Felder forum :) And I’m waiting for my finish to dry.
All forms of energy ultimately end in heat, so yes, 8KW of energy coming in results in 8KW of heat in your shop.
?
A 3KW 5HP motor produces 3KW worth of heat – electrical resistance heat in the power cord and motor windings, sliding friction heat in the bearings and air friction in parts rotating in air. Even the work output of the motor – the cutting,
sanding, blowing, etc., ultimately ends up as heat – if you stick your hand in a pile of just cut sawdust, it will be quite warm from the cutting tool friction and the forced deformation of the wood.
?
It is accurate to say that a 3KW motor itself doesn’t itself give off 10,000 BTU of heat, but if you factor all of the losses in the system and especially the work output into whatever the motor is doing, you end up with 10,000 BTU of heat
in your room as a result of the motor running. It’s counter-intuitive, but it’s true.
?
I am not an expert but I am pretty sure this is not correct.
“?That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.”
Only a small portion of power being consumed is generating heat.
?Mark, I understand the thermal mass.? I often run the saw or shaper for an hour or two straight.? Sucking 110F air into my shop would definitely be a problem.? When running I have a 5HP dust collector and a 5HP saw, shaper, or sander running.
That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.? My lighting is another 2.3kw.? 1kw of electric is 3412btu so 10kw of electric in is about 34K btu.? Over 3 tons of AC.? If I ran machines
all the time and wanted to keep it cool when it's over 110F I would have had to have 10 tons of AC per the mechanical engineer.? That's without dumping exhaust outside.? Now if I were heating the machine heat would work for me and not against me.
?
|
Brian, where then did the energy go?? Idling a saw energy is mostly losses in the motor.? The rest is moving the air near the blade and that heats the
air??
?
This is a fundamental physics reality.? Not really debatable…joe
?
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From: [email protected] < [email protected]>
On Behalf Of Brian Lamb
Sent: Saturday, May 23, 2020 8:05 AM
To: [email protected]
Subject: Re: [FOG] Building a closet for dust collector
?
No, not all energy to do the work is converted to heat. For example, your saw idles at say 1hp, a heavy cut is consuming 3hp, that’s a 2hp or 1500W increase. Picture a 1500W heater, which efficiently converts all it’s watts to heat, do
you really think you pumped out 1500W of heat into the shop taking a cut with the saw? No, you might have gotten 100W of heat in the cut, but everything else was consumed doing the actual work.
?
?
That is where I started. At least 80% of the energy is consumed in doing work otherwise it is a pretty inefficient setup. But these guys have convinced me that the energy used to do the work is also released as thermal energy in the environment.
I have never thought of this before. It makes sense to me.
On May 23, 2020, at 10:36 AM, Brian Lamb <blamb11@...> wrote:
?You all are missing the point that a lot of the hp/watts is actually consumed doing the “work”, whether it’s sawing the wood, jointing, planing, sanding, lighting or even compressing air. It takes force to do most of these things (not
lighting of course), and the force of the blade cutting through the wood is a large percentage of the watts consumed. Yes, there is always a heat load, but it’s not anywhere close to 100% of consumed power…. even here in AZ where it will be 111? later this
week.
?
?
I think perhaps the issue then is the usual workload of a typical shop. Although in an it system things are, I imagine, a bit more stable in terms of draw and power use,
that is not the case for most shops not in a factory environment. We tend to turn on and off equipment and not be steadily throwing plank after plank in rapid succession thorough a saw at max force leading to an actual nameplate type draw. Whereas computer
fans are typically more blunt force objects running at max 100% of the time to account for a potentially catastrophic consequence of failing to control heat in a limited space and the consequences of those failures. And so, I may allow for a total heat release
into your shop for the sake of argument, but even then, the draw is variable and subsequently the heat release. If the OP is concerned about utilizing a motor and dealing with the heat for 100% utilization, he is probably 1) not using the right equipment as
Felder doesn’t spec the duty as 100%, and 2) in the wrong forum and needs to be talking to factory owners.
But in more real world situations, we don’t use 100% draw even when we are using machines most of the time, turn them off between runs, have leaks under a doors, windows
to radiate out, poor insulation to not contain heat or cold, and a myriad of other issues. Sure, running motors will increase heat but it’s not a 1:1 in any of our shops, and especially not at nameplate levels.
I think you just said mostly what I did – that the energy turns into heat, just not entirely in the motor itself.?
?
8KW of electricity into a room turns into 27,000 of BTU in that room, either directly or indirectly, unless that motor is driving a shaft through a wall where some of that energy is converted into heat somewhere else. That 8KW of heat may
not stay in the room due to diffusion through the room walls and ceiling, but it’s put into the room, no if’s, and’s, or but’s, just as if you had an 8KW electric resistance heater.
?
Energy is not returned to the environment on the return leg – the neutral wire in a single phase 120v world, or the other hot legs in a 240v or 3-phase world. If the energy is not needed for work output or system inefficiency losses it
is not drawn in the first place; e.g. a 5HP/3KW motor has a free-running power consumption value of maybe 1KW, and that power consumption increases when the motor is asked to do work. Only when the motor is fully loaded does it draw 3KW of power. Yes there
is voltage drop on the electrical service wiring and yes there is heat generated from that lost energy, but that’s a different problem in a different room. Power distribution is sized to deliver nominal voltage at the end point, factoring in losses in distribution.
?
RE designing HVAC based on electrical load – yes, this is exactly how it’s done. My day job is in IT, part of which includes managing a datacenter and it’s power and cooling. Cooling load is absolutely sized based on power draw of computing
equipment as well as the expected environmental factors. ??
?
Small spaces like workshops – small closed systems – will show the temperature rise of power consumption more quickly than a larger system which has a lot more thermal sinking capability.
?
I agree it’s complicated, and I’m glad nothing is simple on the Felder forum, which I’m new to. There are few things in life that can truly be expressed simply.? Learning stuff – the reason I joined the group – happens when the complexity
is welcomed.??
?
No. While you may be correct that the differences between potential energy and kinetic reach equilibrium through heat transfer, it’s not so clear cut as the statement that an 8kw input to a motor yields 8kw of heat within a workshop. Within
systems there are many components, heat sinks, and losses. So for example, the spinning motor creates heat in bearings through friction, the blade creates heat through friction in the wood and drag through air, some energy is passed through entirely in the
electrical supply and leaves the system and recovers its potential in a ground, some energy is absorbed through wood fibers/saw dust and heat sinked. Heat is lost through inefficient insulation, air drafts, radiation through windows etc. Some energy is released
slowly and muddies the results like the specific heat of cast iron and sawdust. All causes, yes, 8kw input leads to 8kw of heat. But the closed system needs to be very large which simply is out of line with a real world workshop. I don’t know much about sizing
hvac but I don’t think this is the way to do it.
Nothing is simple on a Felder forum :) And I’m waiting for my finish to dry.
All forms of energy ultimately end in heat, so yes, 8KW of energy coming in results in 8KW of heat in your shop.
?
A 3KW 5HP motor produces 3KW worth of heat – electrical resistance heat in the power cord and motor windings, sliding friction heat in the bearings and air friction in parts rotating in air. Even the work output of the motor – the cutting,
sanding, blowing, etc., ultimately ends up as heat – if you stick your hand in a pile of just cut sawdust, it will be quite warm from the cutting tool friction and the forced deformation of the wood.
?
It is accurate to say that a 3KW motor itself doesn’t itself give off 10,000 BTU of heat, but if you factor all of the losses in the system and especially the work output into whatever the motor is doing, you end up with 10,000 BTU of heat
in your room as a result of the motor running. It’s counter-intuitive, but it’s true.
?
I am not an expert but I am pretty sure this is not correct.
“?That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.”
Only a small portion of power being consumed is generating heat.
?Mark, I understand the thermal mass.? I often run the saw or shaper for an hour or two straight.? Sucking 110F air into my shop would definitely be a problem.? When running I have a 5HP dust collector and a 5HP saw, shaper, or sander running.
That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.? My lighting is another 2.3kw.? 1kw of electric is 3412btu so 10kw of electric in is about 34K btu.? Over 3 tons of AC.? If I ran machines
all the time and wanted to keep it cool when it's over 110F I would have had to have 10 tons of AC per the mechanical engineer.? That's without dumping exhaust outside.? Now if I were heating the machine heat would work for me and not against me.
?
?
|
The work is lumen output and the lumens hit a surface and that surface warms from the lumens.
?
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From: [email protected] < [email protected]>
On Behalf Of Brian Lamb
Sent: Saturday, May 23, 2020 9:22 AM
To: [email protected]
Subject: Re: [FOG] Building a closet for dust collector
?
Agreed, the horse has heat, but in the case of lighting, the lumens is the “work”, we get the same amount of lumens from 15 watts (LED) as we do 100W of incandescent. Put the 100W vs. the 15W in your box and the temperature rise will not
be the same.
All this is moot anyway, we are talking about HVAC loads and what is practical. In AZ where we have massive heat loads in the summer, exhausting air outside is a foolish endeavor and doing the best to deaden the acoustics is worthwhile.
?
On May 23, 2020, at 9:10 AM, mark thomas <murkyd@...> wrote:
?
Brian, put your hand on a horse that's just standing around doing nothing, and then put your hand on a horse that's been working.? ?You'll feel the heat.
Part of what's confusing is the timeframe of heat moving, and again the system boundary.? In the light bulb case, some of the energy is quickly and locally converted directly to heat, and that's what you think of as the "waste" or "loss".? ?
An incandescent may convert 90% to heat immediately and the remaining 10% later.? ?An LED may convert 10% to heat immediately and the remaining 90% later.? ?But the energy moved into photons is just delayed and distant heat.? The photons stream across the room
and hit a surface, and some of those photons heat up the surface, and some bounce off and then land somewhere else, and heat up that surface, etc...
This is actually very easy to demonstrate.? Make?an opaque box (closed system) and put a 100w incandescent bulb in it and measure temperature rise over time X, then do the same with a 100W LED bulb.? The results will be identical.? ? ?
?
|
You think no energy is consumed shearing the wood fibers? Maybe I’m an idiot, but I don’t think all energy is equated to heat gain in the building. There is theoretical and there is practical.
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Brian, where then did the energy go?? Idling a saw energy is mostly losses in the motor.? The rest is moving the air near the blade and that heats the air??? ? This is a fundamental physics reality.? Not really debatable…joe ? ? No, not all energy to do the work is converted to heat. For example, your saw idles at say 1hp, a heavy cut is consuming 3hp, that’s a 2hp or 1500W increase. Picture a 1500W heater, which efficiently converts all it’s watts to heat, do you really think you pumped out 1500W of heat into the shop taking a cut with the saw? No, you might have gotten 100W of heat in the cut, but everything else was consumed doing the actual work. ? ? That is where I started. At least 80% of the energy is consumed in doing work otherwise it is a pretty inefficient setup. But these guys have convinced me that the energy used to do the work is also released as thermal energy in the environment. I have never thought of this before. It makes sense to me.
On May 23, 2020, at 10:36 AM, Brian Lamb <blamb11@...> wrote:
?You all are missing the point that a lot of the hp/watts is actually consumed doing the “work”, whether it’s sawing the wood, jointing, planing, sanding, lighting or even compressing air. It takes force to do most of these things (not lighting of course), and the force of the blade cutting through the wood is a large percentage of the watts consumed. Yes, there is always a heat load, but it’s not anywhere close to 100% of consumed power…. even here in AZ where it will be 111? later this week. ? ? I think perhaps the issue then is the usual workload of a typical shop. Although in an it system things are, I imagine, a bit more stable in terms of draw and power use, that is not the case for most shops not in a factory environment. We tend to turn on and off equipment and not be steadily throwing plank after plank in rapid succession thorough a saw at max force leading to an actual nameplate type draw. Whereas computer fans are typically more blunt force objects running at max 100% of the time to account for a potentially catastrophic consequence of failing to control heat in a limited space and the consequences of those failures. And so, I may allow for a total heat release into your shop for the sake of argument, but even then, the draw is variable and subsequently the heat release. If the OP is concerned about utilizing a motor and dealing with the heat for 100% utilization, he is probably 1) not using the right equipment as Felder doesn’t spec the duty as 100%, and 2) in the wrong forum and needs to be talking to factory owners. But in more real world situations, we don’t use 100% draw even when we are using machines most of the time, turn them off between runs, have leaks under a doors, windows to radiate out, poor insulation to not contain heat or cold, and a myriad of other issues. Sure, running motors will increase heat but it’s not a 1:1 in any of our shops, and especially not at nameplate levels.
I think you just said mostly what I did – that the energy turns into heat, just not entirely in the motor itself.? ? 8KW of electricity into a room turns into 27,000 of BTU in that room, either directly or indirectly, unless that motor is driving a shaft through a wall where some of that energy is converted into heat somewhere else. That 8KW of heat may not stay in the room due to diffusion through the room walls and ceiling, but it’s put into the room, no if’s, and’s, or but’s, just as if you had an 8KW electric resistance heater. ? Energy is not returned to the environment on the return leg – the neutral wire in a single phase 120v world, or the other hot legs in a 240v or 3-phase world. If the energy is not needed for work output or system inefficiency losses it is not drawn in the first place; e.g. a 5HP/3KW motor has a free-running power consumption value of maybe 1KW, and that power consumption increases when the motor is asked to do work. Only when the motor is fully loaded does it draw 3KW of power. Yes there is voltage drop on the electrical service wiring and yes there is heat generated from that lost energy, but that’s a different problem in a different room. Power distribution is sized to deliver nominal voltage at the end point, factoring in losses in distribution. ? RE designing HVAC based on electrical load – yes, this is exactly how it’s done. My day job is in IT, part of which includes managing a datacenter and it’s power and cooling. Cooling load is absolutely sized based on power draw of computing equipment as well as the expected environmental factors. ?? ? Small spaces like workshops – small closed systems – will show the temperature rise of power consumption more quickly than a larger system which has a lot more thermal sinking capability. ? I agree it’s complicated, and I’m glad nothing is simple on the Felder forum, which I’m new to. There are few things in life that can truly be expressed simply.? Learning stuff – the reason I joined the group – happens when the complexity is welcomed.?? ? No. While you may be correct that the differences between potential energy and kinetic reach equilibrium through heat transfer, it’s not so clear cut as the statement that an 8kw input to a motor yields 8kw of heat within a workshop. Within systems there are many components, heat sinks, and losses. So for example, the spinning motor creates heat in bearings through friction, the blade creates heat through friction in the wood and drag through air, some energy is passed through entirely in the electrical supply and leaves the system and recovers its potential in a ground, some energy is absorbed through wood fibers/saw dust and heat sinked. Heat is lost through inefficient insulation, air drafts, radiation through windows etc. Some energy is released slowly and muddies the results like the specific heat of cast iron and sawdust. All causes, yes, 8kw input leads to 8kw of heat. But the closed system needs to be very large which simply is out of line with a real world workshop. I don’t know much about sizing hvac but I don’t think this is the way to do it. Nothing is simple on a Felder forum :) And I’m waiting for my finish to dry.
All forms of energy ultimately end in heat, so yes, 8KW of energy coming in results in 8KW of heat in your shop. ? A 3KW 5HP motor produces 3KW worth of heat – electrical resistance heat in the power cord and motor windings, sliding friction heat in the bearings and air friction in parts rotating in air. Even the work output of the motor – the cutting, sanding, blowing, etc., ultimately ends up as heat – if you stick your hand in a pile of just cut sawdust, it will be quite warm from the cutting tool friction and the forced deformation of the wood. ? It is accurate to say that a 3KW motor itself doesn’t itself give off 10,000 BTU of heat, but if you factor all of the losses in the system and especially the work output into whatever the motor is doing, you end up with 10,000 BTU of heat in your room as a result of the motor running. It’s counter-intuitive, but it’s true. ? I am not an expert but I am pretty sure this is not correct. “?That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.” Only a small portion of power being consumed is generating heat. ?Mark, I understand the thermal mass.? I often run the saw or shaper for an hour or two straight.? Sucking 110F air into my shop would definitely be a problem.? When running I have a 5HP dust collector and a 5HP saw, shaper, or sander running. That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.? My lighting is another 2.3kw.? 1kw of electric is 3412btu so 10kw of electric in is about 34K btu.? Over 3 tons of AC.? If I ran machines all the time and wanted to keep it cool when it's over 110F I would have had to have 10 tons of AC per the mechanical engineer.? That's without dumping exhaust outside.? Now if I were heating the machine heat would work for me and not against me.
?
?
|
Maybe it’s better to think of work and heat as both being kinetic energy. “Work” is potential energy converted to mechanical energy which is kinetic and potential energy into the system. This potential energy can be stepwise converted
down the line to heat as the final result or other work along the way. And the road goes on until heat equilibrium or all particles in the system are moving at the same speed so no transfers can occur and all potential is exhausted. Universally, this is the
theoretical “heat death” although that’s a topic to explore on your own.
Get
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Brian, the point is doing the work creates heat too.? Take a milling machine.? The motor has inefficiency, heat. The motor moves things in the mill, some friction some more heat.? Then the cutter removes metal, more heat. The coolant
cools the metal warming the coolant. 100% of the energy in ends up as either potential energy like raising a hoist, or heat. With lighting the energy either turns into light which shines on objects and heats them or it is wasted in the LED driver etc.
?
You all are missing the point that a lot of the hp/watts is actually consumed doing the “work”, whether it’s sawing the wood, jointing, planing, sanding, lighting or even compressing air. It takes force to do most of these things (not
lighting of course), and the force of the blade cutting through the wood is a large percentage of the watts consumed. Yes, there is always a heat load, but it’s not anywhere close to 100% of consumed power…. even here in AZ where it will be 111? later this
week.
Brian Lamb
blamb11@...
?
?
You all are missing the point that a lot of the hp/watts is actually consumed doing the “work”, whether it’s sawing the wood, jointing, planing, sanding, lighting or even compressing air. It takes force to do most of these things (not
lighting of course), and the force of the blade cutting through the wood is a large percentage of the watts consumed. Yes, there is always a heat load, but it’s not anywhere close to 100% of consumed power…. even here in AZ where it will be 111? later this
week.
?
?
I think perhaps the issue then is the usual workload of a typical shop. Although in an it system things are, I imagine, a bit more stable in terms of draw and power use,
that is not the case for most shops not in a factory environment. We tend to turn on and off equipment and not be steadily throwing plank after plank in rapid succession thorough a saw at max force leading to an actual nameplate type draw. Whereas computer
fans are typically more blunt force objects running at max 100% of the time to account for a potentially catastrophic consequence of failing to control heat in a limited space and the consequences of those failures. And so, I may allow for a total heat release
into your shop for the sake of argument, but even then, the draw is variable and subsequently the heat release. If the OP is concerned about utilizing a motor and dealing with the heat for 100% utilization, he is probably 1) not using the right equipment as
Felder doesn’t spec the duty as 100%, and 2) in the wrong forum and needs to be talking to factory owners.
But in more real world situations, we don’t use 100% draw even when we are using machines most of the time, turn them off between runs, have leaks under a doors, windows
to radiate out, poor insulation to not contain heat or cold, and a myriad of other issues. Sure, running motors will increase heat but it’s not a 1:1 in any of our shops, and especially not at nameplate levels.
I think you just said mostly what I did – that the energy turns into heat, just not entirely in the motor itself.?
?
8KW of electricity into a room turns into 27,000 of BTU in that room, either directly or indirectly, unless that motor is driving a shaft through a wall where some of that energy is converted into heat somewhere else. That 8KW of heat
may not stay in the room due to diffusion through the room walls and ceiling, but it’s put into the room, no if’s, and’s, or but’s, just as if you had an 8KW electric resistance heater.
?
Energy is not returned to the environment on the return leg – the neutral wire in a single phase 120v world, or the other hot legs in a 240v or 3-phase world. If the energy is not needed for work output or system inefficiency losses it
is not drawn in the first place; e.g. a 5HP/3KW motor has a free-running power consumption value of maybe 1KW, and that power consumption increases when the motor is asked to do work. Only when the motor is fully loaded does it draw 3KW of power. Yes there
is voltage drop on the electrical service wiring and yes there is heat generated from that lost energy, but that’s a different problem in a different room. Power distribution is sized to deliver nominal voltage at the end point, factoring in losses in distribution.
?
RE designing HVAC based on electrical load – yes, this is exactly how it’s done. My day job is in IT, part of which includes managing a datacenter and it’s power and cooling. Cooling load is absolutely sized based on power draw of computing
equipment as well as the expected environmental factors. ??
?
Small spaces like workshops – small closed systems – will show the temperature rise of power consumption more quickly than a larger system which has a lot more thermal sinking capability.
?
I agree it’s complicated, and I’m glad nothing is simple on the Felder forum, which I’m new to. There are few things in life that can truly be expressed simply.? Learning stuff – the reason I joined the group – happens when the complexity
is welcomed.??
?
No. While you may be correct that the differences between potential energy and kinetic reach equilibrium through heat transfer, it’s not so clear cut as the statement that an 8kw input to a motor yields 8kw of heat within a workshop.
Within systems there are many components, heat sinks, and losses. So for example, the spinning motor creates heat in bearings through friction, the blade creates heat through friction in the wood and drag through air, some energy is passed through entirely
in the electrical supply and leaves the system and recovers its potential in a ground, some energy is absorbed through wood fibers/saw dust and heat sinked. Heat is lost through inefficient insulation, air drafts, radiation through windows etc. Some energy
is released slowly and muddies the results like the specific heat of cast iron and sawdust. All causes, yes, 8kw input leads to 8kw of heat. But the closed system needs to be very large which simply is out of line with a real world workshop. I don’t know much
about sizing hvac but I don’t think this is the way to do it.
Nothing is simple on a Felder forum :) And I’m waiting for my finish to dry.
All forms of energy ultimately end in heat, so yes, 8KW of energy coming in results in 8KW of heat in your shop.
?
A 3KW 5HP motor produces 3KW worth of heat – electrical resistance heat in the power cord and motor windings, sliding friction heat in the bearings and air friction in parts rotating in air. Even the work output of the motor – the cutting,
sanding, blowing, etc., ultimately ends up as heat – if you stick your hand in a pile of just cut sawdust, it will be quite warm from the cutting tool friction and the forced deformation of the wood.
?
It is accurate to say that a 3KW motor itself doesn’t itself give off 10,000 BTU of heat, but if you factor all of the losses in the system and especially the work output into whatever the motor is doing, you end up with 10,000 BTU of
heat in your room as a result of the motor running. It’s counter-intuitive, but it’s true.
?
I am not an expert but I am pretty sure this is not correct.
“?That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.”
Only a small portion of power being consumed is generating heat.
?Mark, I understand the thermal mass.? I often run the saw or shaper for an hour or two straight.? Sucking 110F air into my shop would definitely be a problem.? When running I have a 5HP dust collector and a 5HP saw, shaper, or sander
running. That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.? My lighting is another 2.3kw.? 1kw of electric is 3412btu so 10kw of electric in is about 34K btu.? Over 3 tons of AC.? If I ran
machines all the time and wanted to keep it cool when it's over 110F I would have had to have 10 tons of AC per the mechanical engineer.? That's without dumping exhaust outside.? Now if I were heating the machine heat would work for me and not against me.
?
|
And practically speaking, most of this has very little to do with calculating a simple answer for heat gain in your workshop.
Get
toggle quoted message
Show quoted text
Maybe it’s better to think of work and heat as both being kinetic energy. “Work” is potential energy converted to mechanical energy which is kinetic and potential energy into the system. This potential energy can be stepwise converted
down the line to heat as the final result or other work along the way. And the road goes on until heat equilibrium or all particles in the system are moving at the same speed so no transfers can occur and all potential is exhausted. Universally, this is the
theoretical “heat death” although that’s a topic to explore on your own.
Get
Brian, the point is doing the work creates heat too.? Take a milling machine.? The motor has inefficiency, heat. The motor moves things in the mill, some friction some more heat.? Then the cutter removes metal, more heat. The coolant
cools the metal warming the coolant. 100% of the energy in ends up as either potential energy like raising a hoist, or heat. With lighting the energy either turns into light which shines on objects and heats them or it is wasted in the LED driver etc.
?
You all are missing the point that a lot of the hp/watts is actually consumed doing the “work”, whether it’s sawing the wood, jointing, planing, sanding, lighting or even compressing air. It takes force to do most of these things (not
lighting of course), and the force of the blade cutting through the wood is a large percentage of the watts consumed. Yes, there is always a heat load, but it’s not anywhere close to 100% of consumed power…. even here in AZ where it will be 111? later this
week.
Brian Lamb
blamb11@...
?
?
You all are missing the point that a lot of the hp/watts is actually consumed doing the “work”, whether it’s sawing the wood, jointing, planing, sanding, lighting or even compressing air. It takes force to do most of these things (not
lighting of course), and the force of the blade cutting through the wood is a large percentage of the watts consumed. Yes, there is always a heat load, but it’s not anywhere close to 100% of consumed power…. even here in AZ where it will be 111? later this
week.
?
?
I think perhaps the issue then is the usual workload of a typical shop. Although in an it system things are, I imagine, a bit more stable in terms of draw and power
use, that is not the case for most shops not in a factory environment. We tend to turn on and off equipment and not be steadily throwing plank after plank in rapid succession thorough a saw at max force leading to an actual nameplate type draw. Whereas computer
fans are typically more blunt force objects running at max 100% of the time to account for a potentially catastrophic consequence of failing to control heat in a limited space and the consequences of those failures. And so, I may allow for a total heat release
into your shop for the sake of argument, but even then, the draw is variable and subsequently the heat release. If the OP is concerned about utilizing a motor and dealing with the heat for 100% utilization, he is probably 1) not using the right equipment as
Felder doesn’t spec the duty as 100%, and 2) in the wrong forum and needs to be talking to factory owners.
But in more real world situations, we don’t use 100% draw even when we are using machines most of the time, turn them off between runs, have leaks under a doors, windows
to radiate out, poor insulation to not contain heat or cold, and a myriad of other issues. Sure, running motors will increase heat but it’s not a 1:1 in any of our shops, and especially not at nameplate levels.
I think you just said mostly what I did – that the energy turns into heat, just not entirely in the motor itself.?
?
8KW of electricity into a room turns into 27,000 of BTU in that room, either directly or indirectly, unless that motor is driving a shaft through a wall where some of that energy is converted into heat somewhere else. That 8KW of heat
may not stay in the room due to diffusion through the room walls and ceiling, but it’s put into the room, no if’s, and’s, or but’s, just as if you had an 8KW electric resistance heater.
?
Energy is not returned to the environment on the return leg – the neutral wire in a single phase 120v world, or the other hot legs in a 240v or 3-phase world. If the energy is not needed for work output or system inefficiency losses
it is not drawn in the first place; e.g. a 5HP/3KW motor has a free-running power consumption value of maybe 1KW, and that power consumption increases when the motor is asked to do work. Only when the motor is fully loaded does it draw 3KW of power. Yes there
is voltage drop on the electrical service wiring and yes there is heat generated from that lost energy, but that’s a different problem in a different room. Power distribution is sized to deliver nominal voltage at the end point, factoring in losses in distribution.
?
RE designing HVAC based on electrical load – yes, this is exactly how it’s done. My day job is in IT, part of which includes managing a datacenter and it’s power and cooling. Cooling load is absolutely sized based on power draw of computing
equipment as well as the expected environmental factors. ??
?
Small spaces like workshops – small closed systems – will show the temperature rise of power consumption more quickly than a larger system which has a lot more thermal sinking capability.
?
I agree it’s complicated, and I’m glad nothing is simple on the Felder forum, which I’m new to. There are few things in life that can truly be expressed simply.? Learning stuff – the reason I joined the group – happens when the complexity
is welcomed.??
?
No. While you may be correct that the differences between potential energy and kinetic reach equilibrium through heat transfer, it’s not so clear cut as the statement that an 8kw input to a motor yields 8kw of heat within a workshop.
Within systems there are many components, heat sinks, and losses. So for example, the spinning motor creates heat in bearings through friction, the blade creates heat through friction in the wood and drag through air, some energy is passed through entirely
in the electrical supply and leaves the system and recovers its potential in a ground, some energy is absorbed through wood fibers/saw dust and heat sinked. Heat is lost through inefficient insulation, air drafts, radiation through windows etc. Some energy
is released slowly and muddies the results like the specific heat of cast iron and sawdust. All causes, yes, 8kw input leads to 8kw of heat. But the closed system needs to be very large which simply is out of line with a real world workshop. I don’t know much
about sizing hvac but I don’t think this is the way to do it.
Nothing is simple on a Felder forum :) And I’m waiting for my finish to dry.
All forms of energy ultimately end in heat, so yes, 8KW of energy coming in results in 8KW of heat in your shop.
?
A 3KW 5HP motor produces 3KW worth of heat – electrical resistance heat in the power cord and motor windings, sliding friction heat in the bearings and air friction in parts rotating in air. Even the work output of the motor – the cutting,
sanding, blowing, etc., ultimately ends up as heat – if you stick your hand in a pile of just cut sawdust, it will be quite warm from the cutting tool friction and the forced deformation of the wood.
?
It is accurate to say that a 3KW motor itself doesn’t itself give off 10,000 BTU of heat, but if you factor all of the losses in the system and especially the work output into whatever the motor is doing, you end up with 10,000 BTU
of heat in your room as a result of the motor running. It’s counter-intuitive, but it’s true.
?
I am not an expert but I am pretty sure this is not correct.
“?That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.”
Only a small portion of power being consumed is generating heat.
?Mark, I understand the thermal mass.? I often run the saw or shaper for an hour or two straight.? Sucking 110F air into my shop would definitely be a problem.? When running I have a 5HP dust collector and a 5HP saw, shaper, or sander
running. That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.? My lighting is another 2.3kw.? 1kw of electric is 3412btu so 10kw of electric in is about 34K btu.? Over 3 tons of AC.? If I ran
machines all the time and wanted to keep it cool when it's over 110F I would have had to have 10 tons of AC per the mechanical engineer.? That's without dumping exhaust outside.? Now if I were heating the machine heat would work for me and not against me.
?
|
For a circular saw cutting maybe5 minutes an hour, yes. For continuous duty use of things like dust collectors, vacuum hold down tables, and CNC equipment running multi-hour jobs it can get real hot real fast.?
?
?
And practically speaking, most of this has very little to do with calculating a simple answer for heat gain in your workshop.
toggle quoted message
Show quoted text
From: [email protected] <[email protected]> on behalf of Michael Tagge via groups.io <mike.j.tagge@...>
Sent: Tuesday, May 26, 2020 11:07:23 AM
To: [email protected] <[email protected]>
Subject: Re: [FOG] Building a closet for dust collector
Maybe it’s better to think of work and heat as both being kinetic energy. “Work” is potential energy converted to mechanical energy which is kinetic and potential energy into the system. This potential energy can be stepwise converted down
the line to heat as the final result or other work along the way. And the road goes on until heat equilibrium or all particles in the system are moving at the same speed so no transfers can occur and all potential is exhausted. Universally, this is the theoretical
“heat death” although that’s a topic to explore on your own.
Brian, the point is doing the work creates heat too.? Take a milling machine.? The motor has inefficiency, heat. The motor moves things in the mill, some friction some more heat.? Then the cutter removes metal, more heat. The coolant
cools the metal warming the coolant. 100% of the energy in ends up as either potential energy like raising a hoist, or heat. With lighting the energy either turns into light which shines on objects and heats them or it is wasted in the LED driver etc.
?
You all are missing the point that a lot of the hp/watts is actually consumed doing the “work”, whether it’s sawing the wood, jointing, planing, sanding, lighting or even compressing air. It takes force to do most of these things (not
lighting of course), and the force of the blade cutting through the wood is a large percentage of the watts consumed. Yes, there is always a heat load, but it’s not anywhere close to 100% of consumed power…. even here in AZ where it will be 111? later this
week.
Brian Lamb
blamb11@...
?
?
You all are missing the point that a lot of the hp/watts is actually consumed doing the “work”, whether it’s sawing the wood, jointing, planing, sanding, lighting or even compressing air. It takes force to do most of these things (not
lighting of course), and the force of the blade cutting through the wood is a large percentage of the watts consumed. Yes, there is always a heat load, but it’s not anywhere close to 100% of consumed power…. even here in AZ where it will be 111? later this
week.
?
?
I think perhaps the issue then is the usual workload of a typical shop. Although in an it system things are, I imagine, a bit more stable in terms of draw and power use, that is not
the case for most shops not in a factory environment. We tend to turn on and off equipment and not be steadily throwing plank after plank in rapid succession thorough a saw at max force leading to an actual nameplate type draw. Whereas computer fans are typically
more blunt force objects running at max 100% of the time to account for a potentially catastrophic consequence of failing to control heat in a limited space and the consequences of those failures. And so, I may allow for a total heat release into your shop
for the sake of argument, but even then, the draw is variable and subsequently the heat release. If the OP is concerned about utilizing a motor and dealing with the heat for 100% utilization, he is probably 1) not using the right equipment as Felder doesn’t
spec the duty as 100%, and 2) in the wrong forum and needs to be talking to factory owners.
But in more real world situations, we don’t use 100% draw even when we are using machines most of the time, turn them off between runs, have leaks under a doors, windows to radiate
out, poor insulation to not contain heat or cold, and a myriad of other issues. Sure, running motors will increase heat but it’s not a 1:1 in any of our shops, and especially not at nameplate levels.
I think you just said mostly what I did – that the energy turns into heat, just not entirely in the motor itself.?
?
8KW of electricity into a room turns into 27,000 of BTU in that room, either directly or indirectly, unless that motor is driving a shaft through a wall where some of that energy is converted into heat somewhere else. That 8KW of heat
may not stay in the room due to diffusion through the room walls and ceiling, but it’s put into the room, no if’s, and’s, or but’s, just as if you had an 8KW electric resistance heater.
?
Energy is not returned to the environment on the return leg – the neutral wire in a single phase 120v world, or the other hot legs in a 240v or 3-phase world. If the energy is not needed for work output or system inefficiency losses it
is not drawn in the first place; e.g. a 5HP/3KW motor has a free-running power consumption value of maybe 1KW, and that power consumption increases when the motor is asked to do work. Only when the motor is fully loaded does it draw 3KW of power. Yes there
is voltage drop on the electrical service wiring and yes there is heat generated from that lost energy, but that’s a different problem in a different room. Power distribution is sized to deliver nominal voltage at the end point, factoring in losses in distribution.
?
RE designing HVAC based on electrical load – yes, this is exactly how it’s done. My day job is in IT, part of which includes managing a datacenter and it’s power and cooling. Cooling load is absolutely sized based on power draw of computing
equipment as well as the expected environmental factors. ??
?
Small spaces like workshops – small closed systems – will show the temperature rise of power consumption more quickly than a larger system which has a lot more thermal sinking capability.
?
I agree it’s complicated, and I’m glad nothing is simple on the Felder forum, which I’m new to. There are few things in life that can truly be expressed simply.? Learning stuff – the reason I joined the group – happens when the complexity
is welcomed.??
?
No. While you may be correct that the differences between potential energy and kinetic reach equilibrium through heat transfer, it’s not so clear cut as the statement that an 8kw input to a motor yields 8kw of heat within a workshop.
Within systems there are many components, heat sinks, and losses. So for example, the spinning motor creates heat in bearings through friction, the blade creates heat through friction in the wood and drag through air, some energy is passed through entirely
in the electrical supply and leaves the system and recovers its potential in a ground, some energy is absorbed through wood fibers/saw dust and heat sinked. Heat is lost through inefficient insulation, air drafts, radiation through windows etc. Some energy
is released slowly and muddies the results like the specific heat of cast iron and sawdust. All causes, yes, 8kw input leads to 8kw of heat. But the closed system needs to be very large which simply is out of line with a real world workshop. I don’t know much
about sizing hvac but I don’t think this is the way to do it.
Nothing is simple on a Felder forum :) And I’m waiting for my finish to dry.
All forms of energy ultimately end in heat, so yes, 8KW of energy coming in results in 8KW of heat in your shop.
?
A 3KW 5HP motor produces 3KW worth of heat – electrical resistance heat in the power cord and motor windings, sliding friction heat in the bearings and air friction in parts rotating in air. Even the work output of the motor – the cutting,
sanding, blowing, etc., ultimately ends up as heat – if you stick your hand in a pile of just cut sawdust, it will be quite warm from the cutting tool friction and the forced deformation of the wood.
?
It is accurate to say that a 3KW motor itself doesn’t itself give off 10,000 BTU of heat, but if you factor all of the losses in the system and especially the work output into whatever the motor is doing, you end up with 10,000 BTU of
heat in your room as a result of the motor running. It’s counter-intuitive, but it’s true.
?
I am not an expert but I am pretty sure this is not correct.
“?That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.”
Only a small portion of power being consumed is generating heat.
?Mark, I understand the thermal mass.? I often run the saw or shaper for an hour or two straight.? Sucking 110F air into my shop would definitely be a problem.? When running I have a 5HP dust collector and a 5HP saw, shaper, or sander
running. That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.? My lighting is another 2.3kw.? 1kw of electric is 3412btu so 10kw of electric in is about 34K btu.? Over 3 tons of AC.? If I ran
machines all the time and wanted to keep it cool when it's over 110F I would have had to have 10 tons of AC per the mechanical engineer.? That's without dumping exhaust outside.? Now if I were heating the machine heat would work for me and not against me.
?
|
The moving wood fibers does consume energy.? The tearing/cutting creates movement and heat. The movement creates heat.? In the end the fiber is moved
and the movements ends up creating heat.
?
toggle quoted message
Show quoted text
From: [email protected] < [email protected]>
On Behalf Of Brian Lamb
Sent: Tuesday, May 26, 2020 8:54 AM
To: [email protected]
Subject: Re: [FOG] Building a closet for dust collector
?
You think no energy is consumed shearing the wood fibers? Maybe I’m an idiot, but I don’t think all energy is equated to heat gain in the building. There is theoretical and there is practical.
?
?
Brian, where then did the energy go?? Idling a saw energy is mostly losses in the motor.? The rest is moving the air near the blade and that heats the
air???
This is a fundamental physics reality.? Not really debatable…joe
No, not all energy to do the work is converted to heat. For example, your saw idles at say 1hp, a heavy cut is consuming 3hp, that’s a 2hp or 1500W increase. Picture a 1500W heater, which efficiently converts all it’s watts to heat, do
you really think you pumped out 1500W of heat into the shop taking a cut with the saw? No, you might have gotten 100W of heat in the cut, but everything else was consumed doing the actual work.
That is where I started. At least 80% of the energy is consumed in doing work otherwise it is a pretty inefficient setup. But these guys have convinced me that the energy used to do the work is also released as thermal energy in the environment.
I have never thought of this before. It makes sense to me.
On May 23, 2020, at 10:36 AM, Brian Lamb <blamb11@...> wrote:
?You all are missing the point that a lot of the hp/watts is actually consumed doing the “work”, whether it’s sawing the wood, jointing, planing, sanding, lighting or even compressing air. It takes force to do most of these things (not
lighting of course), and the force of the blade cutting through the wood is a large percentage of the watts consumed. Yes, there is always a heat load, but it’s not anywhere close to 100% of consumed power…. even here in AZ where it will be 111? later this
week.
I think perhaps the issue then is the usual workload of a typical shop. Although in an it system things are, I imagine, a bit more stable in terms of draw and power use,
that is not the case for most shops not in a factory environment. We tend to turn on and off equipment and not be steadily throwing plank after plank in rapid succession thorough a saw at max force leading to an actual nameplate type draw. Whereas computer
fans are typically more blunt force objects running at max 100% of the time to account for a potentially catastrophic consequence of failing to control heat in a limited space and the consequences of those failures. And so, I may allow for a total heat release
into your shop for the sake of argument, but even then, the draw is variable and subsequently the heat release. If the OP is concerned about utilizing a motor and dealing with the heat for 100% utilization, he is probably 1) not using the right equipment as
Felder doesn’t spec the duty as 100%, and 2) in the wrong forum and needs to be talking to factory owners.
But in more real world situations, we don’t use 100% draw even when we are using machines most of the time, turn them off between runs, have leaks under a doors, windows
to radiate out, poor insulation to not contain heat or cold, and a myriad of other issues. Sure, running motors will increase heat but it’s not a 1:1 in any of our shops, and especially not at nameplate levels.
I think you just said mostly what I did – that the energy turns into heat, just not entirely in the motor itself.?
8KW of electricity into a room turns into 27,000 of BTU in that room, either directly or indirectly, unless that motor is driving a shaft through a wall where some of that energy is converted into heat somewhere else. That 8KW of heat may
not stay in the room due to diffusion through the room walls and ceiling, but it’s put into the room, no if’s, and’s, or but’s, just as if you had an 8KW electric resistance heater.
Energy is not returned to the environment on the return leg – the neutral wire in a single phase 120v world, or the other hot legs in a 240v or 3-phase world. If the energy is not needed for work output or system inefficiency losses it
is not drawn in the first place; e.g. a 5HP/3KW motor has a free-running power consumption value of maybe 1KW, and that power consumption increases when the motor is asked to do work. Only when the motor is fully loaded does it draw 3KW of power. Yes there
is voltage drop on the electrical service wiring and yes there is heat generated from that lost energy, but that’s a different problem in a different room. Power distribution is sized to deliver nominal voltage at the end point, factoring in losses in distribution.
RE designing HVAC based on electrical load – yes, this is exactly how it’s done. My day job is in IT, part of which includes managing a datacenter and it’s power and cooling. Cooling load is absolutely sized based on power draw of computing
equipment as well as the expected environmental factors. ??
Small spaces like workshops – small closed systems – will show the temperature rise of power consumption more quickly than a larger system which has a lot more thermal sinking capability.
I agree it’s complicated, and I’m glad nothing is simple on the Felder forum, which I’m new to. There are few things in life that can truly be expressed simply.? Learning stuff – the reason I joined the group – happens when the complexity
is welcomed.??
No. While you may be correct that the differences between potential energy and kinetic reach equilibrium through heat transfer, it’s not so clear cut as the statement that an 8kw input to a motor yields 8kw of heat within a workshop. Within
systems there are many components, heat sinks, and losses. So for example, the spinning motor creates heat in bearings through friction, the blade creates heat through friction in the wood and drag through air, some energy is passed through entirely in the
electrical supply and leaves the system and recovers its potential in a ground, some energy is absorbed through wood fibers/saw dust and heat sinked. Heat is lost through inefficient insulation, air drafts, radiation through windows etc. Some energy is released
slowly and muddies the results like the specific heat of cast iron and sawdust. All causes, yes, 8kw input leads to 8kw of heat. But the closed system needs to be very large which simply is out of line with a real world workshop. I don’t know much about sizing
hvac but I don’t think this is the way to do it.
Nothing is simple on a Felder forum :) And I’m waiting for my finish to dry.
All forms of energy ultimately end in heat, so yes, 8KW of energy coming in results in 8KW of heat in your shop.
A 3KW 5HP motor produces 3KW worth of heat – electrical resistance heat in the power cord and motor windings, sliding friction heat in the bearings and air friction in parts rotating in air. Even the work output of the motor – the cutting,
sanding, blowing, etc., ultimately ends up as heat – if you stick your hand in a pile of just cut sawdust, it will be quite warm from the cutting tool friction and the forced deformation of the wood.
It is accurate to say that a 3KW motor itself doesn’t itself give off 10,000 BTU of heat, but if you factor all of the losses in the system and especially the work output into whatever the motor is doing, you end up with 10,000 BTU of heat
in your room as a result of the motor running. It’s counter-intuitive, but it’s true.
I am not an expert but I am pretty sure this is not correct.
“?That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.”
Only a small portion of power being consumed is generating heat.
?Mark, I understand the thermal mass.? I often run the saw or shaper for an hour or two straight.? Sucking 110F air into my shop would definitely be a problem.? When running I have a 5HP dust collector and a 5HP saw, shaper, or sander running.
That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.? My lighting is another 2.3kw.? 1kw of electric is 3412btu so 10kw of electric in is about 34K btu.? Over 3 tons of AC.? If I ran machines
all the time and wanted to keep it cool when it's over 110F I would have had to have 10 tons of AC per the mechanical engineer.? That's without dumping exhaust outside.? Now if I were heating the machine heat would work for me and not against me.
?
|
Sorry, another thought.? In our building project the city required us to hire a Mechanical engineer to do the HVAC design.? He modeled the building
itself, insulation, windows, overhead doors, etc to determine how many tons of cooling I needed.? We then sat with me to understand machine usage.? How many HP, how continuous, how many machines at one time, lighting, etc. to determine the heat load.? In the
initial work I talked about running the dust collector (5HP) for 4 hours a day and running 5HP machines 3 hours and a 40HP wide belt for 1 hr per day.? Modeling that and keeping it cool with an outside temp of 115 was going to require 10 tons of cooling, WOW.?
When we said if it was over 110 outside I would not use the machines as much and we said I would not run 4 hours continuously we found I needed 5 tons. I am still worried that 5 tons is not enough even though I have a lot of spray foam and we have foam inside
and on the exterior of the side walls.
?
toggle quoted message
Show quoted text
From: [email protected] < [email protected]>
On Behalf Of Michael Tagge
Sent: Tuesday, May 26, 2020 9:07 AM
To: [email protected]
Subject: Re: [FOG] Building a closet for dust collector
?
Maybe it’s better to think of work and heat as both being kinetic energy. “Work” is potential energy converted to mechanical energy which is kinetic and potential energy into the system. This potential energy can be stepwise converted down
the line to heat as the final result or other work along the way. And the road goes on until heat equilibrium or all particles in the system are moving at the same speed so no transfers can occur and all potential is exhausted. Universally, this is the theoretical
“heat death” although that’s a topic to explore on your own.
Brian, the point is doing the work creates heat too.? Take a milling machine.? The motor has inefficiency, heat. The motor moves things in the mill, some friction some more heat.? Then the cutter removes metal, more heat. The coolant cools
the metal warming the coolant. 100% of the energy in ends up as either potential energy like raising a hoist, or heat. With lighting the energy either turns into light which shines on objects and heats them or it is wasted in the LED driver etc.
?
You all are missing the point that a lot of the hp/watts is actually consumed doing the “work”, whether it’s sawing the wood, jointing, planing, sanding, lighting or even compressing air. It takes force to do most of these things (not
lighting of course), and the force of the blade cutting through the wood is a large percentage of the watts consumed. Yes, there is always a heat load, but it’s not anywhere close to 100% of consumed power…. even here in AZ where it will be 111? later this
week.
Brian Lamb
blamb11@...
?
?
You all are missing the point that a lot of the hp/watts is actually consumed doing the “work”, whether it’s sawing the wood, jointing, planing, sanding, lighting or even compressing air. It takes force to do most of these things (not
lighting of course), and the force of the blade cutting through the wood is a large percentage of the watts consumed. Yes, there is always a heat load, but it’s not anywhere close to 100% of consumed power…. even here in AZ where it will be 111? later this
week.
?
?
I think perhaps the issue then is the usual workload of a typical shop. Although in an it system things are, I imagine, a bit more stable in terms of draw and power use,
that is not the case for most shops not in a factory environment. We tend to turn on and off equipment and not be steadily throwing plank after plank in rapid succession thorough a saw at max force leading to an actual nameplate type draw. Whereas computer
fans are typically more blunt force objects running at max 100% of the time to account for a potentially catastrophic consequence of failing to control heat in a limited space and the consequences of those failures. And so, I may allow for a total heat release
into your shop for the sake of argument, but even then, the draw is variable and subsequently the heat release. If the OP is concerned about utilizing a motor and dealing with the heat for 100% utilization, he is probably 1) not using the right equipment as
Felder doesn’t spec the duty as 100%, and 2) in the wrong forum and needs to be talking to factory owners.
But in more real world situations, we don’t use 100% draw even when we are using machines most of the time, turn them off between runs, have leaks under a doors, windows
to radiate out, poor insulation to not contain heat or cold, and a myriad of other issues. Sure, running motors will increase heat but it’s not a 1:1 in any of our shops, and especially not at nameplate levels.
I think you just said mostly what I did – that the energy turns into heat, just not entirely in the motor itself.?
?
8KW of electricity into a room turns into 27,000 of BTU in that room, either directly or indirectly, unless that motor is driving a shaft through a wall where some of that energy is converted into heat somewhere else. That 8KW of heat
may not stay in the room due to diffusion through the room walls and ceiling, but it’s put into the room, no if’s, and’s, or but’s, just as if you had an 8KW electric resistance heater.
?
Energy is not returned to the environment on the return leg – the neutral wire in a single phase 120v world, or the other hot legs in a 240v or 3-phase world. If the energy is not needed for work output or system inefficiency losses it
is not drawn in the first place; e.g. a 5HP/3KW motor has a free-running power consumption value of maybe 1KW, and that power consumption increases when the motor is asked to do work. Only when the motor is fully loaded does it draw 3KW of power. Yes there
is voltage drop on the electrical service wiring and yes there is heat generated from that lost energy, but that’s a different problem in a different room. Power distribution is sized to deliver nominal voltage at the end point, factoring in losses in distribution.
?
RE designing HVAC based on electrical load – yes, this is exactly how it’s done. My day job is in IT, part of which includes managing a datacenter and it’s power and cooling. Cooling load is absolutely sized based on power draw of computing
equipment as well as the expected environmental factors. ??
?
Small spaces like workshops – small closed systems – will show the temperature rise of power consumption more quickly than a larger system which has a lot more thermal sinking capability.
?
I agree it’s complicated, and I’m glad nothing is simple on the Felder forum, which I’m new to. There are few things in life that can truly be expressed simply.? Learning stuff – the reason I joined the group – happens when the complexity
is welcomed.??
?
No. While you may be correct that the differences between potential energy and kinetic reach equilibrium through heat transfer, it’s not so clear cut as the statement that an 8kw input to a motor yields 8kw of heat within a workshop. Within
systems there are many components, heat sinks, and losses. So for example, the spinning motor creates heat in bearings through friction, the blade creates heat through friction in the wood and drag through air, some energy is passed through entirely in the
electrical supply and leaves the system and recovers its potential in a ground, some energy is absorbed through wood fibers/saw dust and heat sinked. Heat is lost through inefficient insulation, air drafts, radiation through windows etc. Some energy is released
slowly and muddies the results like the specific heat of cast iron and sawdust. All causes, yes, 8kw input leads to 8kw of heat. But the closed system needs to be very large which simply is out of line with a real world workshop. I don’t know much about sizing
hvac but I don’t think this is the way to do it.
Nothing is simple on a Felder forum :) And I’m waiting for my finish to dry.
All forms of energy ultimately end in heat, so yes, 8KW of energy coming in results in 8KW of heat in your shop.
?
A 3KW 5HP motor produces 3KW worth of heat – electrical resistance heat in the power cord and motor windings, sliding friction heat in the bearings and air friction in parts rotating in air. Even the work output of the motor – the cutting,
sanding, blowing, etc., ultimately ends up as heat – if you stick your hand in a pile of just cut sawdust, it will be quite warm from the cutting tool friction and the forced deformation of the wood.
?
It is accurate to say that a 3KW motor itself doesn’t itself give off 10,000 BTU of heat, but if you factor all of the losses in the system and especially the work output into whatever the motor is doing, you end up with 10,000 BTU of
heat in your room as a result of the motor running. It’s counter-intuitive, but it’s true.
?
I am not an expert but I am pretty sure this is not correct.
“?That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.”
Only a small portion of power being consumed is generating heat.
?Mark, I understand the thermal mass.? I often run the saw or shaper for an hour or two straight.? Sucking 110F air into my shop would definitely be a problem.? When running I have a 5HP dust collector and a 5HP saw, shaper, or sander
running. That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.? My lighting is another 2.3kw.? 1kw of electric is 3412btu so 10kw of electric in is about 34K btu.? Over 3 tons of AC.? If I ran
machines all the time and wanted to keep it cool when it's over 110F I would have had to have 10 tons of AC per the mechanical engineer.? That's without dumping exhaust outside.? Now if I were heating the machine heat would work for me and not against me.
?
|
Im running way behind in reading posts so this may have been covered already. I am not an expert either, however, I believe the laws of thermodynamics state that energy cannot be created or destroyed, only changed in form. ?Wouldn’t that mean that like a chemistry reaction (or any math for that matter) equation the input must be the same as the output. ?So if all of the input energy becomes output heat, how do we account for the work (force and movement) accomplished? ?Yes a car engine creates friction and heat when burning complex hydrocarbons but it also moves itself and a payload. ?
toggle quoted message
Show quoted text
On May 22, 2020, at 8:42 PM, TJ Cornish < tj@...> wrote:
All forms of energy ultimately end in heat, so yes, 8KW of energy coming in results in 8KW of heat in your shop.
?
A 3KW 5HP motor produces 3KW worth of heat – electrical resistance heat in the power cord and motor windings, sliding friction heat in the bearings and air friction in parts rotating in air. Even the work output of the motor – the cutting,
sanding, blowing, etc., ultimately ends up as heat – if you stick your hand in a pile of just cut sawdust, it will be quite warm from the cutting tool friction and the forced deformation of the wood.
?
It is accurate to say that a 3KW motor itself doesn’t itself give off 10,000 BTU of heat, but if you factor all of the losses in the system and especially the work output into whatever the motor is doing, you end up with 10,000 BTU of heat
in your room as a result of the motor running. It’s counter-intuitive, but it’s true.
?
I am not an expert but I am pretty sure this is not correct.
“?That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.”
Only a small portion of power being consumed is generating heat.
?Mark, I understand the thermal mass.? I often run the saw or shaper for an hour or two straight.? Sucking 110F air into my shop would definitely be a problem.? When running I have a 5HP dust collector and a 5HP saw, shaper, or sander running.
That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.? My lighting is another 2.3kw.? 1kw of electric is 3412btu so 10kw of electric in is about 34K btu.? Over 3 tons of AC.? If I ran machines
all the time and wanted to keep it cool when it's over 110F I would have had to have 10 tons of AC per the mechanical engineer.? That's without dumping exhaust outside.? Now if I were heating the machine heat would work for me and not against me.
|
On Sat, May 30, 2020 at 10:52 AM, Gerald Yungling wrote:
Im running way behind in reading posts so this may have been covered already.
Yes, many people have stated the laws of physics on this thread, and given countless examples.? A few people seem not to believe it, but that's not likely to be resolved here.??
|
Gerald, this has been covered pretty thoroughly, especially out of the musings of a bunch of woodworkers.?
The only thing I can think to add is to consider the fact that an object moving in space will keep traveling almost indefinitely because there is nothing to slow it down. On earth, everything else - every motion or force ultimately breaks down to heat: friction, deformation, etc. All of that heat contributes to your environment. How much heat that is depends on load, duty cycle, and the efficiency of the operation - e.g. the difference between cutting 12” off a board with a saw vs sanding 12” off the board, but whatever energy you use heats up your space.?
Whether that is a problem requiring action depends on your circumstances.?
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Show quoted text
On May 30, 2020, at 12:52 PM, Gerald Yungling via groups.io <gyungling@...> wrote:
? Im running way behind in reading posts so this may have been covered already. I am not an expert either, however, I believe the laws of thermodynamics state that energy cannot be created or destroyed, only changed in form. ?Wouldn’t that mean that like a chemistry reaction (or any math for that matter) equation the input must be the same as the output. ?So if all of the input energy becomes output heat, how do we account for the work (force and movement) accomplished? ?Yes a car engine creates friction and heat when burning complex hydrocarbons but it also moves itself and a payload. ?
Gerald?
On May 22, 2020, at 8:42 PM, TJ Cornish < tj@...> wrote:
All forms of energy ultimately end in heat, so yes, 8KW of energy coming in results in 8KW of heat in your shop.
?
A 3KW 5HP motor produces 3KW worth of heat – electrical resistance heat in the power cord and motor windings, sliding friction heat in the bearings and air friction in parts rotating in air. Even the work output of the motor – the cutting,
sanding, blowing, etc., ultimately ends up as heat – if you stick your hand in a pile of just cut sawdust, it will be quite warm from the cutting tool friction and the forced deformation of the wood.
?
It is accurate to say that a 3KW motor itself doesn’t itself give off 10,000 BTU of heat, but if you factor all of the losses in the system and especially the work output into whatever the motor is doing, you end up with 10,000 BTU of heat
in your room as a result of the motor running. It’s counter-intuitive, but it’s true.
?
I am not an expert but I am pretty sure this is not correct.
“?That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.”
Only a small portion of power being consumed is generating heat.
?Mark, I understand the thermal mass.? I often run the saw or shaper for an hour or two straight.? Sucking 110F air into my shop would definitely be a problem.? When running I have a 5HP dust collector and a 5HP saw, shaper, or sander running.
That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.? My lighting is another 2.3kw.? 1kw of electric is 3412btu so 10kw of electric in is about 34K btu.? Over 3 tons of AC.? If I ran machines
all the time and wanted to keep it cool when it's over 110F I would have had to have 10 tons of AC per the mechanical engineer.? That's without dumping exhaust outside.? Now if I were heating the machine heat would work for me and not against me.
|
Gerald, if the work is say moving an elevator car up, then there is stored potential energy that can be released when the car comes down.? There are
also losses from friction which turns to heat.?? In woodworking, the work that say a planer does is to cut the wood fibers.? That involves moving the wood through the machine, cutting fibers, and flinging the cut fibers away from the knife.? There are also
losses to friction, creating air turbulence, etc.? But there really is no storing of energy, so the energy that went in has to balance and the only way it could leave is heat.? The movement of things creates potential energy and if they stop moving it’s because
something, usually friction, stopped them.
?
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From: [email protected] < [email protected]>
On Behalf Of Gerald Yungling via groups.io
Sent: Saturday, May 30, 2020 10:53 AM
To: [email protected]
Subject: Re: [FOG] Building a closet for dust collector
?
Im running way behind in reading posts so this may have been covered already. I am not an expert either, however, I believe the laws of thermodynamics state that energy cannot be created or destroyed, only changed in form. ?Wouldn’t that
mean that like a chemistry reaction (or any math for that matter) equation the input must be the same as the output. ?So if all of the input energy becomes output heat, how do we account for the work (force and movement) accomplished? ?Yes a car engine creates
friction and heat when burning complex hydrocarbons but it also moves itself and a payload. ?
Gerald?
?
On May 22, 2020, at 8:42 PM, TJ Cornish <tj@...> wrote:
All forms of energy ultimately end in heat, so yes, 8KW of energy coming in results in 8KW of heat in your shop.
?
A 3KW 5HP motor produces 3KW worth of heat – electrical resistance heat in the power cord and motor windings, sliding friction heat in the bearings and air friction in parts rotating in air. Even the work output of the motor – the cutting,
sanding, blowing, etc., ultimately ends up as heat – if you stick your hand in a pile of just cut sawdust, it will be quite warm from the cutting tool friction and the forced deformation of the wood.
?
It is accurate to say that a 3KW motor itself doesn’t itself give off 10,000 BTU of heat, but if you factor all of the losses in the system and especially the work output into whatever the motor is doing, you end up with 10,000 BTU of heat
in your room as a result of the motor running. It’s counter-intuitive, but it’s true.
?
I am not an expert but I am pretty sure this is not correct.
“?That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.”
Only a small portion of power being consumed is generating heat.
?Mark, I understand the thermal mass.? I often run the saw or shaper for an hour or two straight.? Sucking 110F air into my shop would definitely be a problem.? When running I have a 5HP dust collector and a 5HP saw, shaper, or sander running.
That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.? My lighting is another 2.3kw.? 1kw of electric is 3412btu so 10kw of electric in is about 34K btu.? Over 3 tons of AC.? If I ran machines
all the time and wanted to keep it cool when it's over 110F I would have had to have 10 tons of AC per the mechanical engineer.? That's without dumping exhaust outside.? Now if I were heating the machine heat would work for me and not against me.
|
Yes an object in motion and an object at rest... ?But what put that object in motion? ?If all the force was accounted for by heat loss, how did potential become kinetic? ?Again, I’m no physicists, this is an honest question.?
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On May 30, 2020, at 1:29 PM, TJ Cornish < tj@...> wrote: Gerald, this has been covered pretty thoroughly, especially out of the musings of a bunch of woodworkers.?
The only thing I can think to add is to consider the fact that an object moving in space will keep traveling almost indefinitely because there is nothing to slow it down. On earth, everything else - every motion or force ultimately breaks down to heat: friction, deformation, etc. All of that heat contributes to your environment. How much heat that is depends on load, duty cycle, and the efficiency of the operation - e.g. the difference between cutting 12” off a board with a saw vs sanding 12” off the board, but whatever energy you use heats up your space.?
Whether that is a problem requiring action depends on your circumstances.? On May 30, 2020, at 12:52 PM, Gerald Yungling via <gyungling@...> wrote:
? Im running way behind in reading posts so this may have been covered already. I am not an expert either, however, I believe the laws of thermodynamics state that energy cannot be created or destroyed, only changed in form. ?Wouldn’t that mean that like a chemistry reaction (or any math for that matter) equation the input must be the same as the output. ?So if all of the input energy becomes output heat, how do we account for the work (force and movement) accomplished? ?Yes a car engine creates friction and heat when burning complex hydrocarbons but it also moves itself and a payload. ?
Gerald?
On May 22, 2020, at 8:42 PM, TJ Cornish < tj@...> wrote:
All forms of energy ultimately end in heat, so yes, 8KW of energy coming in results in 8KW of heat in your shop.
?
A 3KW 5HP motor produces 3KW worth of heat – electrical resistance heat in the power cord and motor windings, sliding friction heat in the bearings and air friction in parts rotating in air. Even the work output of the motor – the cutting,
sanding, blowing, etc., ultimately ends up as heat – if you stick your hand in a pile of just cut sawdust, it will be quite warm from the cutting tool friction and the forced deformation of the wood.
?
It is accurate to say that a 3KW motor itself doesn’t itself give off 10,000 BTU of heat, but if you factor all of the losses in the system and especially the work output into whatever the motor is doing, you end up with 10,000 BTU of heat
in your room as a result of the motor running. It’s counter-intuitive, but it’s true.
?
I am not an expert but I am pretty sure this is not correct.
“?That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.”
Only a small portion of power being consumed is generating heat.
?Mark, I understand the thermal mass.? I often run the saw or shaper for an hour or two straight.? Sucking 110F air into my shop would definitely be a problem.? When running I have a 5HP dust collector and a 5HP saw, shaper, or sander running.
That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.? My lighting is another 2.3kw.? 1kw of electric is 3412btu so 10kw of electric in is about 34K btu.? Over 3 tons of AC.? If I ran machines
all the time and wanted to keep it cool when it's over 110F I would have had to have 10 tons of AC per the mechanical engineer.? That's without dumping exhaust outside.? Now if I were heating the machine heat would work for me and not against me.
|
Gerald,
I was the first one to question Joe’s statement here, bad engineer, as it is not intuitively obvious.
There should be no question that energy cannot be created nor destroyed per the first law of thermodynamics. So energy put into a closed system will be preserved.
Based on this principle, a board cut into two boards or the sawdust produced in the process has no energy after it cools to the ambient temp. A motor (after it stops spinning) and all associates wiring, after they cool to ambient temp of the room, have no energy. You can expand this to air movement, saw blade temp, etc.
Unless energy is converted and retained, as in spring force or angular momentum (fly wheel), or potential energy (raise something); all energy consumed ends up raising the temp of the room.
Hope this helps.
Imran
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On Jun 5, 2020, at 12:08 AM, Gerald Yungling via groups.io <gyungling@...> wrote: ? Yes an object in motion and an object at rest... ?But what put that object in motion? ?If all the force was accounted for by heat loss, how did potential become kinetic? ?Again, I’m no physicists, this is an honest question.? On May 30, 2020, at 1:29 PM, TJ Cornish < tj@...> wrote: Gerald, this has been covered pretty thoroughly, especially out of the musings of a bunch of woodworkers.?
The only thing I can think to add is to consider the fact that an object moving in space will keep traveling almost indefinitely because there is nothing to slow it down. On earth, everything else - every motion or force ultimately breaks down to heat: friction, deformation, etc. All of that heat contributes to your environment. How much heat that is depends on load, duty cycle, and the efficiency of the operation - e.g. the difference between cutting 12” off a board with a saw vs sanding 12” off the board, but whatever energy you use heats up your space.?
Whether that is a problem requiring action depends on your circumstances.? On May 30, 2020, at 12:52 PM, Gerald Yungling via <gyungling@...> wrote:
? Im running way behind in reading posts so this may have been covered already. I am not an expert either, however, I believe the laws of thermodynamics state that energy cannot be created or destroyed, only changed in form. ?Wouldn’t that mean that like a chemistry reaction (or any math for that matter) equation the input must be the same as the output. ?So if all of the input energy becomes output heat, how do we account for the work (force and movement) accomplished? ?Yes a car engine creates friction and heat when burning complex hydrocarbons but it also moves itself and a payload. ?
Gerald?
On May 22, 2020, at 8:42 PM, TJ Cornish < tj@...> wrote:
All forms of energy ultimately end in heat, so yes, 8KW of energy coming in results in 8KW of heat in your shop.
?
A 3KW 5HP motor produces 3KW worth of heat – electrical resistance heat in the power cord and motor windings, sliding friction heat in the bearings and air friction in parts rotating in air. Even the work output of the motor – the cutting,
sanding, blowing, etc., ultimately ends up as heat – if you stick your hand in a pile of just cut sawdust, it will be quite warm from the cutting tool friction and the forced deformation of the wood.
?
It is accurate to say that a 3KW motor itself doesn’t itself give off 10,000 BTU of heat, but if you factor all of the losses in the system and especially the work output into whatever the motor is doing, you end up with 10,000 BTU of heat
in your room as a result of the motor running. It’s counter-intuitive, but it’s true.
?
I am not an expert but I am pretty sure this is not correct.
“?That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.”
Only a small portion of power being consumed is generating heat.
?Mark, I understand the thermal mass.? I often run the saw or shaper for an hour or two straight.? Sucking 110F air into my shop would definitely be a problem.? When running I have a 5HP dust collector and a 5HP saw, shaper, or sander running.
That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.? My lighting is another 2.3kw.? 1kw of electric is 3412btu so 10kw of electric in is about 34K btu.? Over 3 tons of AC.? If I ran machines
all the time and wanted to keep it cool when it's over 110F I would have had to have 10 tons of AC per the mechanical engineer.? That's without dumping exhaust outside.? Now if I were heating the machine heat would work for me and not against me.
|
 I believe we reduced by 15 or so db with simple 1/2” mdf and 2x4. Totally worth it.? Taylor Donsker www.tdonsker.com 818.424.9046
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On Jun 5, 2020, at 5:51 AM, imranindiana via groups.io <imranindiana@...> wrote:
? Gerald,
I was the first one to question Joe’s statement here, bad engineer, as it is not intuitively obvious.
There should be no question that energy cannot be created nor destroyed per the first law of thermodynamics. So energy put into a closed system will be preserved.
Based on this principle, a board cut into two boards or the sawdust produced in the process has no energy after it cools to the ambient temp. A motor (after it stops spinning) and all associates wiring, after they cool to ambient temp of the room, have no energy. You can expand this to air movement, saw blade temp, etc.
Unless energy is converted and retained, as in spring force or angular momentum (fly wheel), or potential energy (raise something); all energy consumed ends up raising the temp of the room.
Hope this helps.
Imran
On Jun 5, 2020, at 12:08 AM, Gerald Yungling via groups.io <gyungling@...> wrote:
? Yes an object in motion and an object at rest... ?But what put that object in motion? ?If all the force was accounted for by heat loss, how did potential become kinetic? ?Again, I’m no physicists, this is an honest question.? On May 30, 2020, at 1:29 PM, TJ Cornish < tj@...> wrote: Gerald, this has been covered pretty thoroughly, especially out of the musings of a bunch of woodworkers.?
The only thing I can think to add is to consider the fact that an object moving in space will keep traveling almost indefinitely because there is nothing to slow it down. On earth, everything else - every motion or force ultimately breaks down to heat: friction, deformation, etc. All of that heat contributes to your environment. How much heat that is depends on load, duty cycle, and the efficiency of the operation - e.g. the difference between cutting 12” off a board with a saw vs sanding 12” off the board, but whatever energy you use heats up your space.?
Whether that is a problem requiring action depends on your circumstances.? On May 30, 2020, at 12:52 PM, Gerald Yungling via <gyungling@...> wrote:
? Im running way behind in reading posts so this may have been covered already. I am not an expert either, however, I believe the laws of thermodynamics state that energy cannot be created or destroyed, only changed in form. ?Wouldn’t that mean that like a chemistry reaction (or any math for that matter) equation the input must be the same as the output. ?So if all of the input energy becomes output heat, how do we account for the work (force and movement) accomplished? ?Yes a car engine creates friction and heat when burning complex hydrocarbons but it also moves itself and a payload. ?
Gerald?
On May 22, 2020, at 8:42 PM, TJ Cornish < tj@...> wrote:
All forms of energy ultimately end in heat, so yes, 8KW of energy coming in results in 8KW of heat in your shop.
?
A 3KW 5HP motor produces 3KW worth of heat – electrical resistance heat in the power cord and motor windings, sliding friction heat in the bearings and air friction in parts rotating in air. Even the work output of the motor – the cutting,
sanding, blowing, etc., ultimately ends up as heat – if you stick your hand in a pile of just cut sawdust, it will be quite warm from the cutting tool friction and the forced deformation of the wood.
?
It is accurate to say that a 3KW motor itself doesn’t itself give off 10,000 BTU of heat, but if you factor all of the losses in the system and especially the work output into whatever the motor is doing, you end up with 10,000 BTU of heat
in your room as a result of the motor running. It’s counter-intuitive, but it’s true.
?
I am not an expert but I am pretty sure this is not correct.
“?That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.”
Only a small portion of power being consumed is generating heat.
?Mark, I understand the thermal mass.? I often run the saw or shaper for an hour or two straight.? Sucking 110F air into my shop would definitely be a problem.? When running I have a 5HP dust collector and a 5HP saw, shaper, or sander running.
That's about 8KW of electric coming in that all turns to heat, either motor heat, or friction heat from cutting etc.? My lighting is another 2.3kw.? 1kw of electric is 3412btu so 10kw of electric in is about 34K btu.? Over 3 tons of AC.? If I ran machines
all the time and wanted to keep it cool when it's over 110F I would have had to have 10 tons of AC per the mechanical engineer.? That's without dumping exhaust outside.? Now if I were heating the machine heat would work for me and not against me.
|
imran
Joe Jensen
Gerald Yungling