Blog post: swansont: I Have Figured Out Your Evil Plan

As part of the money saving in the sequester, DoD facilities have been told their thermostats will be raised a high as 80ºF (26.7ºC). We've avoided going that high thus far, because we're going to do some mitigation like installing window tinting to reduce the overall heat load (plus there's the leverage of operational equipment that can't be allowed to overheat, but I don't know if that card is being played and we humans are peripheral beneficiaries)

The rumor is that the chill water in the heat exchanger is going to be set at a much higher temperature than before, at around 14ºC, which is slightly below the typical dewpoint for the summer air. This saves money because condensing water out of the air takes a lot of energy. Warm, wet air (27ºC, ~50% relative humidity) will have upwards of 11 grams of water per kg of air, and air at a comfortable 22ºC and 30% RH has but 5 grams. The heat of vaporization is around 2.5 kJ/gram of water, while for air the specific heat is around 1 kJ/kg-ºC, so cooling from 27ºC down to 22 removes about a third of the energy as compared to condensing 6g of water, so if you can basically eliminate the water removal by only cooling to the dewpoint, you will save quite a bit of money. (They aren't completely avoiding the removal of water, but the new system scales it back by quite a bit). For the recirculated air, they are just removing whatever we add from our evaporating perspiration and spilled coffee.

Unfortunately, 1 kg of completely saturated air at 14ºC still has 10 grams of water in it, and that represents 60% RH at 22ºC, which is really sticky. I'll bet the mold will love it, though.
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