Experimental Measurements of Heat and Mass Transport in Heat Pipe Wicks

A novel experimental approach is developed for characterizing the performance of heat pipe wick structures. Mass transport measurements of the working fluid are obtained in addition to the temperature field in the porous wicks, under the action of a discrete heat source (evaporator). Open, partially submerged wicks are studied under partially saturated conditions, simulating normal heat pipe operation. The submerged portion of the wick simulates the condenser in a heat pipe. A vertical wick orientation, where the lift is in opposition to gravity, was selected to test the wicks under the most demanding conditions. The working fluid, supplied from the condenser pool, evaporates from the wick surface, and is condensed and collected into a collector separate from the pool, to yield mass flow rate results. Thus the liquid-pumping capability of the wick, coupled with flow impedance, can be measured with this approach at various applied heat fluxes. A simplified analytical model for the heat flow paths in the wick structure is also presented to explain the experimental measurements.