Marcos Buenijo wrote:
(*) Most chilled water systems I've seen operate at a high vacuum to drive the rapid evaporation of a store of water. Chilled water flows through a heat exchanger contained in this store of water for continual cooling. Solid adsorbents like silica gel or zeolite are used in some systems to drive the evaporation. However, other systems use liquid desiccants. I believe a good system can be had using inexpensive aqueous calcium chloride here. This system can be more easily fabricated than most others I've considered. Heat can be used to regenerate the liquid desiccant after it drains by gravity into a heating vessel. The water vapor released can be condensed (with some heat recovery for useful purposes), and the cool condensate returned to the water vessel. The concentrated liquid desiccant is returned to the top of a packing column by a low power pump where the desiccant continually is exposed to the water vapor given off from the water vessel. The more dilute desiccant collects at the bottom of the packing column (after absorbing water vapor) where it drains back to the heater in a closed cycle. There is a slightly higher pressure on the heater side, so the fluid column consisting of the water vapor condensate and the desiccant pump (with check valve) are used to isolate this pressure. The pressure is also used to force the water vapor condensate back up into the water vessel. A compact system can be evacuated using steam to displace the air (to generate the high vacuum required).