[jeff5may]

For a more effective liquid dehumidifier, we want to move the most water per btu or watt used to regenerate the dessicant. This means the regenerator should only be heated enough to drive the water from the solution to a concentration where solid salt would not form. Raising the brine temp to above 115 degF would make the hexahydrate want to give up water to form tetrahydrate, so if you had a regenerator with a large enough surface area, you could evaporate the brine out to around 50% strength effectively at or above that temperature. Higher regenerator temperatures equate to smaller surface areas with the same evaporation rate. Most commercial units shoot for around 180 degF to make the evaporation highly effective.

Indoors, the solution must have a certain strength to effectively pull water from the air. At normal room temps, this equates to somewhere above 40% minimum concentration. At 40%, the solution will dry the air down close to 40% relative humidity. More CaCl2 in the water equates to more dehumidifying power per liter.

Above 45% strength, the solution will tend to form crystals in the dehumidifier (which would tend to warm the liquid as they re-dissolved into the water) as the solution cools below 105 degF. So there is a sweet spot (between 40 and 45 percent concentration) that the solution should stay to avoid all manner of phase-change mayhem, assuming that solid crystal formation is unwanted.