Osmotic heat pipe - Problems and promises

Various problems associated with the operation of a heat pipe based on osmotic pumping for improved performance are examined. The discussion stresses the concept of osmotic heat pipes and important potential limitations on their performance. The heat pipe encloses a membrane, the annular space is filled with a salt solution, and water permeates by osmosis through the membrane and flows in the annular space; heat is removed at the bottom and condensed pure water is transported to the membrane by the capillary action of the wick. The limitations are such that heat transfer is limited by membrane permeability, the salt tends to concentrate in the evaporator region rather than the membrane area where it is needed to promote osmosis, the optimum solute concentration must be determined to obtain maximum buoyancy forces without crystallizing the salt, and the condensate must not block the vapor flow. A tentative geometry to meet these conditions is presented.