High heat flux removal using biporous heat pipe evaporators

The objective of this dissertation is to develop an advanced heat pipe-evaporating surface that can handle heat fluxes as high as 1kW/cm2 at intermediate junction temperatures for future Naval thermal management needs.; Thermophysical properties and evaporation heat transfer coefficient of monoporous and biporous wicks were measured. Apparatuses for measuring permeability, capillary pressure, thermal conductivity, wick heat transfer performance tests, and an apparatus for visualization of vapor flows were built in this work. Capillary pressure was found to decrease as particle diameter increases while permeability was found to increase with particle diameter. Thermal conductivity of monoporous samples was found not to depend on the particle diameter. Vapor permeability was found to increase with increasing cluster diameter and effective thermal conductivity of biporous samples was found to decrease with increasing the cluster diameter. Porosity of monoporous and biporous samples was found not to depend on the particle or cluster diameter.; Biporous wicks with different particle and cluster diameters, evaporator thicknesses, and evaporator radii were tested with degassed distilled water at an average vapor pressure of 0.07bar. The results show that monoporous evaporators perform better than biporous evaporators for heat fluxes below 300W/cm2; however, at heat fluxes higher than 300W/cm 2, the monoporous evaporators suddenly dryout and a run-away of the wall temperature occurs. Biporous evaporators are shown to operate safely at heat fluxes many times greater than CHF. Evaporator radius was found to have only a little effect on heat transfer performances while wick thickness was found to be one of the most important parameters.; A thick biporous wick was found that was able to remove 1340+/-187W/cm 2 at a wall temperature of 177+/-13°C and a thin biporous wick that removed 636+/-58W/cm2 at 110+/-5°C wall temperature. The results show that thin biporous wicks behave similar to monoporous wicks with extended evaporation area, and the thick biporous wicks remove the heat with a 2-D spreading of evaporation front within the wick.