Novel liquid desiccant-based heat exchanger using pervaporative membrane tube

Air conditioning methods that include a process of dehumidifying an air stream and then exposing the air stream to a liquid desiccant in a conditioner are well established. In these units, a portion of the air stream that is dehumidified flows to another unit that acts as an evaporative chiller and causes the portion of the dehumidified air stream to absorb water from a water containing source and thereby cool a heat transfer fluid. There is therefore a need for a three-fluid heat exchanger, where air, liquid desiccant and a heat transfer fluid. Three fluid heat exchangers are known and typically utilize plate and frame configurations. These configurations have several key disadvantages. First of all, they provide dead zone were fluids are entrained and provide poor transfer properties. In order to render these plate and frame designs effective there is a need for very narrow flow channels which provide high pressure drop in the system and must be overcome with additional pumping energy. And they also suffer from poor sealing around the edges – quite simply they have extensive, long, continuous edges – that must be sealed. Salt solutions can be corrosive, and the plates need to be pressed at extremities to maintain sealing. Sealing these flat plate systems is a difficult, non-trivial engineering challenge. This invention provides for a simple three fluid heat exchanger.

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