Experimental study on capillary pumping performance of porous wicks for loop heat pipe

The aim of this study is to investigate the capillary pumping performance of porous wick for the use of loop heat pipe by developing a method that studying the capillary pumping amount real time changing curve which is recorded by electronic balance and computer. The porous wicks are prepared by powder metallurgy method using type 255 pure nickels as the material. The working fluids used in this study are water and acetone. The porous wicks investigated in this study include 3 with the same porosity and 4 with different porosities. The result shows that capillary pumping amount changing curve of porous wick can be described with an exponential increase equation. The offset and the opposite of amplitude of the exponential increase equation are all equated to the total capillary pumping amount of the porous wick. The time constant of the exponential increase equation is related to the capillary pumping rate which indicates the comprehensive properties of capillary pressure and flow resistance of the system of porous wick and working fluid. Capillary pumping rate is found to increase with the increasing porosities of the porous wicks. When porosities of the porous wicks are the same, those with tighter granules and straighter channels in the microstructures are found to have better capillary pumping performance. (C) 2010 Elsevier Inc. All rights reserved.