An Experimental Study in the Fundamentals of Evaporation from Porous Structure

Abstract

The heat pipe is one of the applications for evaporative heat transfer in porous media. The metal wick in a heat pipe has high thermal conductivity and water as a working fluid has high latent heat of evaporation that enhances the cooling effects. Evaporation rate affects the heat transfer capacity and efficiency of the heat pipe. Therefore, evaporative heat transfer from porous media in heat pipes and vapor chambers plays an important role in determining their overall performance. This paper is to study the fundamental evaporation characteristics and its relationship with regard to the different porosities. Samples with different random configurations, thickness ranging from 5mm to 40mm, and balls sizes of the sizes from 5mm to 20mm were tested at three different (60°C, 80°C and 100°C) heat source temperatures. Experiment results were analyzed at steady state arrangement. It was found that the evaporation rate can be improved by varying the particle size and the porosity. Decreasing the layer thickness could enhance the evaporation rate but it has less effect and could cause the drying out to happen easily. To further validate the capability of evaporation from porous structure, the results were compared with the evaporation from water only. It showed the rate of evaporation was obviously increased for evaporation from porous structures.