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PC is setting my room on fire
- Thread starter cwilhelm
- Start date
The power isn't all converted to heat. Some of it is used to do work, and the precise amount depends on the efficiency of the motors.
And the work done by those motors is converted, partially, into kinetic energy in the air, which is then completely (and fairly quickly) converted to heat by viscous drag. The rest (the work lost; not induced into kinetic energy of the air) is immediatly converted to heat. The motors themselves are probably 50% (or more) efficient.
So, in the end, it all ends up as heat.
(these are estimates)
FAN:
1.) Electric power -- 50% --> heat (efficiency of motor, resistive heating, friction of motor/bearings)
2.) Net Electric power ----> motor work --> 40% --> heat from fan blades whipping air (impeller effiency 60%)
3.)Net of the above two--->motor work--->fan blades--->kinetic energy of air---> heat from viscous drag
1.) 50% converted to heat immediatly (motor eff)
2.) 20% converted to heat immediatly (impeller eff)
3.) 30% converted to heat after a few seconds (viscous heating)
I love this type of argument on the internets. Do continue.
I didn't know this. Neat. So if a fan converts 100% of it's electrical draw into heat, wouldn't that make it exactly as efficient at heating a room as a heater at the same wattage? So, putting a fan in a closed room is basically creating a convection oven?
I didn't know this. Neat. So if a fan converts 100% of it's electrical draw into heat, wouldn't that make it exactly as efficient at heating a room as a heater at the same wattage? So, putting a fan in a closed room is basically creating a convection oven?
The fan does contribute to moving air outside the room, so not all of the power it uses is released inside the room though.And the work done by those motors is converted, partially, into kinetic energy in the air, which is then completely (and fairly quickly) converted to heat by viscous drag. The rest (the work lost; not induced into kinetic energy of the air) is immediatly converted to heat. The motors themselves are probably 50% (or more) efficient.
So, in the end, it all ends up as heat.
(these are estimates)
FAN:
1.) Electric power -- 50% --> heat (efficiency of motor, resistive heating, friction of motor/bearings)
2.) Net Electric power ----> motor work --> 40% --> heat from fan blades whipping air (impeller effiency 60%)
3.)Net of the above two--->motor work--->fan blades--->kinetic energy of air---> heat from viscous drag
1.) 50% converted to heat immediatly (motor eff)
2.) 20% converted to heat immediatly (impeller eff)
3.) 30% converted to heat after a few seconds (viscous heating)
Yes.
I love this type of argument on the internets. Do continue.
I didn't know this. Neat. So if a fan converts 100% of it's electrical draw into heat, wouldn't that make it exactly as efficient at heating a room as a heater at the same wattage? So, putting a fan in a closed room is basically creating a convection oven?
It would be the lowest wattage convection oven in history
However, even in a closed room a fan isn't necessarily bad. It will contribute very small amounts of heat (way, way less than a human being) but having the air move over the skin draws heat away faster than stagnant air and also makes sweat evaporate more quickly.
Unless he has the fans in open air, two feet from his doorway, pointing out of the room, I would consider, for all intents and purposes, 99.99%+ to be all of it. I'm assuming they are 120mm fans. If he is using a 3 ft fan or somthing it might be able to push that kinetic energy further.