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Posted by Robert Gammon on Monday, 5 May 2008, at 1:29 p.m.,
in response to Re: geothermal heating/radiant flooring/domestic hot water, posted by Robert Gammon

Water chilled coils (fan coils) is NOT the same as evaporative cooling, I realize that now.

Fan Coils are a new item for me. Hanging a coil in the airstream of the fan from a forced air furnace/ac to supplement the heat/cool of the basic unit is a NEW concept, at least for me. I think that it would have been more appropriate to say that you, Phil, were considering a fan coil solution using your gshp to move cool water thru the coil while a fan forced air across it. This would start to dehumidify once the water temp thru the coil dropped below about 65F. A few minutes of operation and the water temp thru the fan coil COULD drop to 55F. However, a R22 or R410 solution gets the fan coil much colder than than 55F. IMO, The heat of evaporation of the refrigerant is MUCH higher than the heat that cold water can absorb from the coil.

I am aware of only two applications of evaporative cooling, one commercial, one residential. Commercial uses evap cooling (aka Swamp cooler) to cool the hot side of a heat engine, that is it cools the coils with a fine spray of water, some of which will FLASH to steam when it hits the pipes, carrying a large load of heat with it. The finer the mist is, the larger percentage of heat will be absorbed. Residences in the desert SW USA have used evaporative coolers for many many years to evaporate water on screens, to cool and add humidity to the REALLY dry air there. Refrigeration is taking over that application now.

I have walked in Desert Springs CA in the summer, when the indicated temp was well above 110F!! I saw a peak of 119F that trip. It was MORE pleasant to be outside there, in that heat, than it is to be in Houston Tx at the same time of year when the high temps will run about 95F.

Evap cooling is used in Desert Springs and Palm Springs to give outdoor diners a more pleasant environment to rest, relax, and eat. Ultra fine mists are sprayed around the patio to reduce air temps by as much as 20F! However, the systems need regular maintenance to avoid scaling as the mist nozzles are VERY VERY fine and clog easily. Many store owners were not properly maintaining these as they should after months of use, so nozzles plugged totally, or only dripped water instead of spraying it.

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