Taking the Heat

I'm no physicist—a fact that should become immediately apparent. But this latest heat and humidity wave has got me wondering about the amount of heat we generate to stay cool and comfortable. Take the dehumidifier I plugged in near the piano after the piano tuner refused to do his job and gave me a lecture on humidity and wood. The dehumidifier worked great—within hours the stickiness disappeared—and, the room seemed at least 10 degrees warmer. The piano might have been happier, but the room was unbearably hot.

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Dehumidifiers, like air conditioners and refrigerators, are heat pumps—they move heat from one place to the another. Dehumidifiers remove moisture by allowing it to condense on the cold side of the system—the evaporator coil. Unlike fridges and ACs, though, dehumidifiers dump heat into the same air they're pulling heat from, leading one (like me) to assume that the net heat change would be zero. Well, no, as I discovered empirically. The dehumidifier is also consuming energy—it's plugged into the wall, it's doing mechanical work—and it's generating heat. The solution, of course, was to install an air conditioner and simply dump the heat outside (duh).

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Okay, the AC works great, but—isn't there, however small, a heat gain outside? Insignificant, to be sure—especially on this hillside in central New York state, but how about Manhattan? Does anyone know how much New York City, for example, heats up the outdoor air to cool and dehumidify the indoors? It can't be significant, or we'd have heard about it. Right?

In any case, when it comes to personal comfort, I'm increasingly a fan of, well, fans. With a fan, my skin becomes part of the system—it's the evaporator and it cools as the moving air takes away the moisture. As for energy consumption, there's that slice of pizza I had for lunch—and I would have eaten that, anyway.—Tom Klenck

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