We are designing a home evaporative cooling system that is to be used in a coastal tropical location and we need to dry the humid air before entering the cooler by passing it through the desiccant and then regenerate the desiccant by using solar energy to be used again. Please suggest safe materials that can be suitable to such a situation.
I solved the problem of drying gas by flow passing it sequentially through a layer of zeolite, then granulated KOH, mixed with pieces of ceramic to prevent sticking, and finally a layer of phosphorus pentoxide. It should monitor the level of degradation of the dehydration and occasionally calcined zeolite and replace KOH and phosphorus pentoxide. In this manner you can receive the residual water vapor pressure of not more than 10:^-5 torr.
An alternative is freeze-water in liquid nitrogen vapor. The temperature should be keep above the point where oxygen becomes liquid. Therefore, the air flow can not be passed through the tube immersed in liquid nitrogen dewar.
Thanks Alexander
Our problem is not to dry the air completely but to reduce its water content( humidity) and then to pass it through the moist cooling pad. Water vapour will evaporate into the stream of air taking its latent heat of vaporization from the hot air resulting in lowering its temperature to some acceptable comfort limits. The material we are looking for must accept being recycled through a solar regenerator to get rid of the absorbed moisture so as to be used again.
There are a few typical liquid desiccant used in HVAC. Lithium chloride and lithium bromide are the most commonly used chemicals. Corrosion, especially with lithium chloride, can be a problem though.
As Chris suggests, there are probably a few ways to tackle this problem. You might want to consults the standard, ASTM E 104 – 2, Standard Practice for Maintaining Constant Relative Humidity by Means of Aqueous Solutions.
Thank you David, Chris, Philip and Newt for responding to my question.
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