Heat Gain from Electric Motor High?
Heat Gain from Electric Motor High?
(OP)
The ASHRAE estimate for heat gains from electric motors seems very high. For the motor and driven equipment in room equation, they're saying all the real electrical power put into the motor is converted to heat??? What about the energy transferred to the driven equipment? Anyone else think this is way over estimated? If you had a room full of motors, I think this would throw you way off.
Motor & driven in equation:
qem = 2545(P/eff)FumFlm
Fum-use factor
Flm-load factor
(both Fum and Flm are normally 1, unless you want to include known intermittent use and partial loading)
For motor in, driven equipment out, it's the same equ. multiplied by 1-eff, so maybe that would include scenarios where the driven equipment's energy is transferred out of the room, like by a belt for example?
Motor & driven in equation:
qem = 2545(P/eff)FumFlm
Fum-use factor
Flm-load factor
(both Fum and Flm are normally 1, unless you want to include known intermittent use and partial loading)
For motor in, driven equipment out, it's the same equ. multiplied by 1-eff, so maybe that would include scenarios where the driven equipment's energy is transferred out of the room, like by a belt for example?





RE: Heat Gain from Electric Motor High?
If the driven equipment is in the room, then the heat eventually ends up in the room. For a steady state assumption that is the same as the motor input power.
If the heat is dissipated elsewhere (condenser?) then you allow for that.
RE: Heat Gain from Electric Motor High?
RE: Heat Gain from Electric Motor High?
RE: Heat Gain from Electric Motor High?
I'm still reluctant to think that a fan-in-room for example will transfer all the electrical energy into heat. I wonder how much is lost to entropy, eddy currents, turbulence, etc., etc. I guess it's close enough.
RE: Heat Gain from Electric Motor High?
If you take a spoon and stir a cup of water, you will heat it up a very small amount thus; When you stir, you transfer kinetic energy from the spoon to the water. The water will move, then eventually stop moving due to friction - water/water, water/cup, water/air. As the water slows and stops moving, all the kinetic energy is converted to [insert answer here].
So, if your fluid is contained within the room, then all of the work done on that fluid is converted to [same answer as above, I don't want to give it away] within the room. Air, water or turnip juice, it don't matter.
RE: Heat Gain from Electric Motor High?
RE: Heat Gain from Electric Motor High?
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RE: Heat Gain from Electric Motor High?
RE: Heat Gain from Electric Motor High?
RE: Heat Gain from Electric Motor High?
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RE: Heat Gain from Electric Motor High?
Thanks for the input, guys.