RE: Thermodynamics of Evaporative Cooling

Thomas Laupa wrote
>a customer has an "fin fan" cooler (basically a car radiator) that is
overloaded. he can increase gas recovery if he can improve the heat rejection of this device. rather than increasing surface area, he has asked us to explore spraying water on this radiator to increase heat transfer.

I think that this is an excellent idea. Air has a poor heat transfer co-efficient. Consider this. Steam on the other hand can transfer relatively massive amounts of energy upon condensation, by "depositing" latent heat. What we are seeing here is the reverse of the steam condensation process. In your hybrid "finned evaporative cooler" the evaporation of the sprayed water, "withdraws" the latent heat.

Without any data, I would hazard a guess that the capacity would be more than doubled. The other advantage you have is that you already have demin water. If you had normal tap water, you would have scaled the fins in a short time. Corrosion, as another forum member pointed out, would be severe in a mild steel fin assembly. I don't think legionnaires disease or slime would be a major problem, as this would be a once through process. But it would be recommended to check this with a water treatment specialist. (You need very small amount of water, not worth re-circulating it.)

Ahmed Vawda
Process Engineer
Al Khaleej Sugar - Dubai Received on Sat Mar 15 00:43:00 2003