The purpose of this idea is to dehumidify a room or a house, without the use of refrigerants or added heat.

There are two loops of liquid desiccant (Calcium Chloride in water, or similar); one inside the house, and one outside the house.

The loop outside the house goes as follows:

Liquid starts at the pump as a (relatively) dilute liquid, and then passes through an air handler, where the liquid is exposed to atmospheric air.

Some of the water in the liquid evaporates, making the liquid slightly less dilute.

The liquid collects at the bottom of the air handler, and drains through a device containing an osmotic membrane. This device *isn't* arranged like a regular reverse osmosis device, with one inlet and two outlets... instead, it has two inlets and two outlets, similar to a heat exchanger. As the liquid passes through the device (at atmospheric pressure), it becomes more dilute.

After leaving the device, the liquid goes back to the pump.

For the interior loop:

Relatively concentrated liquid desiccant passes through an air handler, exposing it to the air inside the house. The liquid absorbs water from the air, becoming less concentrated.

The liquid then splits into two streams, one going through a pump, and another going through the pressure increasing side of a pressure exchanger. The streams recombine, and (at high pressure) pass through the reverse osmosis device. As the liquid flows through the device, it becomes more concentrated. After the liquid leaves the device, it flows through the pressure decreasing side of the pressure exchanger.

The liquid then returns to the air handler to repeat the cycle.

.

Why this should work:

If the pressure exchange device weren't there, the fluid on both sides of the membrane would be at the same overall pressure. Logically, water would flow through the membrane in whatever direction was necessary to equalize the osmotic pressure.

With the aid of the two air handlers, this will result in humidity moving through the device into the building if it's more humid outside than inside, or humidity flowing out of the building if it's more humid inside than outside.

By making the pressure on one side higher than on the other side, water will flow through the membrane from high pressure to low pressure.

With the aid of the air handlers, this will create a humidity difference between the inside air and outside air... the higher the pressure applied to the membrane, the higher the humidity difference the system can maintain.
-- goldbb, Aug 31 2009

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