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I got a haircut the other day, and noticed that even though it was cool outside, it was uncomfortably warm inside the barber shop. The obvious source of this extra heat was the handheld electric blowdryers used by the hairdressers.
It occured to me that since using electricity to heat air is generally
one of the least economical ways of doing it, there had to be a better solution.
Why not compress air, store it in a thermally insulated tank in a centralized location, and heat it using a heat pump? The heat pump of course could draw the heat out of the room, in effect providing a small amount of air conditioning.
The electric cord and blowdryer combo would be replaced by compressed air hose and nozzle combo.
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I've seen a similar system for vacuuming but not for drying hair. |
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Do you think you could service all the hot air requirements of high end hair dressing? |
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Also I think this would be cheaper. |
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compressed air that is released cools down, so you would have to either super-heat it (with unknown chemical reactions) or store it uncompressed, which would take up a lot of space (how much m³ of air is moved by a hairdryer per hour?) |
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But you could heat a fluid, store it, and use a heat exchanger in the blowers. |
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loonquawl, when air is compressed, it warms up; when that same air is expanded, it cools down by the exact same amount as it warmed. |
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If you compress air, then allow it to cool (by storing it in an uninsulated container for an extended period of time), then expand it, it will be cooler than it was before it was compressed. |
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If you compress air, then add heat to it (any amount of heat, even a little), then expand it, it will be warmer after expansion than it was before it was compressed. It doesn't need to be "super hot." |
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You can't store compressed air uncompressed; what would be the point? Or did you mean store hot air uncompressed? |
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As for heating a fluid, and using heat exchangers in the blowers... that would be heavy, bulky, complicated, and expensive. If the fluid is a gas, you'd need to move large volumes of it to the blowers (and back to the heater) meaning either high pressure or large diameter hoses... which would be heavy and bulky. If the fluid is a liquid, then it would be heavy. And a heat exchanger in every blower would be bulky, heavy and expensive. |
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I was talking about storing hot air uncompressed - not compressing air largely does that... |
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If you compress air to half volume, it gets twice as hot. I guess yoiu would compress it further, making it even hotter. Now all this heat goes to naught, because, as you mentioned, it has to be uncompressed, losing that same amount of heat again. Thus, you would have to heat it even further, which is what i called superheating it. |
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How do you propose to get the air from the container to the blower using something unbulky, unheavy, unexpensive? |
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Air has a specific heat of ~ 0.0013 J/K*cm³, whereas for instance water has ~4.2 J/K*cm³, so about four thousand times more thermal energy per cm³ can be stored in water... |
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This naturally leads to a new idea for improving the efficiency of power generation: Combined Hairdrying and Power. Use the waste heat from power stations to dry people's hair, rather than just dumping it into the atmosphere. [+] |
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And the rather more obvious: use a heat pump to transfer heat into the airstream from a secondary airstream. |
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[+] How would you control the temperature of the heat? Hand dryers have various settings depending on the situation. |
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+ I like it and I don't really know how the technology of it would work, but it sounds good to me. |
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loonquawl, getting the air from the compressed air tank to where it would be used would be done exactly as it's done in a workshop with air powered tools -- metal pipes concealed in the walls would convey the air to work stations, and flexible hoses would convey the air to hand tools. |
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Wrongfellow, power stations are generally not next door to barber shops, making transfering that heat a bit awkward. On the other hand, I suppose you could have a combined heat and power system. |
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(Of course, it would probably be simpler and cheaper to use a heat pump to move heat from the room air of the barbershop into the compressed air). |
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Jscotty, To control the temperature of the air coming out of the hairdryer, there are two ways that I can think of... |
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In the first method, one would need two compressed air supplies -- one which had merely been compressed, and one which had been compressed and then heated. A mixing valve at the hairdresser's station could be adjusted for the proper proportions of heated and unheated compressed air. |
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In the second method, there's one compressed air supply, and a loop of hot hydronic fluid or hot compressed refrigerant. An adjustable heat exchanger at each hairdresser's workstation moves a controlled amount of heat from this fluid into the compressed air stream. |
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I suspect that the dual air supply method would be cheaper and safer. |
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Hmmm.. a heat exchanger beside the hairdresser? Wouldn't they rather have a hair dryer? It would take up less space. |
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It wouldn't work for hand held dryers as the hoses would be unwieldy and unless you have a HYPER eco-friendly neighborhood it wouldn't fly. There are HYPER eco-friendly neighborhoods out there but I doubt those women spend that much money on hair. |
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This would however work very well on the stationary dryers in many salons, so (+). |
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