PROPOSAL OF UTILIZING UNI-DIRECTIONAL POROUS METAL FOR EXTREMELY HIGH HEAT FLUX REMOVAL

摘要

This paper proposes new heat removal devices utilizing uni-directional porous metal under extremely high heat flux conditions. Before designing the detailed structure of the porous media, we discuss some key parameters of the porous media to enable a high heat flux removal over 10 MW/m~2 at a low flow rate of water, which are effective thermal conductivity, permeability, direct liquid supply toward a heat transfer surface, vapor discharge, and contact thermal resistance between the porous medium and the heat transfer surface. Discussions based on the experimental results indicate that utilizing the uni-directional porous media will lead to breakthrough from the view point of its higher thermal conductivity, direct supply of cooling liquid toward the heat transfer surface, discharge of vapor, reduction in flow resistance and the thermal contact resistance. The experimental apparatus to verify this proposal is composed of the coolant supplying pump, the heat transfer test section, and the heat exchanger. Distilled water is used as cooling liquid. The heat transfer test section mainly consists of the heat transfer copper block and the uni-directional porous medium attached onto the heat transfer surface. The uni-directional porous copper has small holes of 0.5 mm in diameter for the liquid supply at the pitch of 1.0mm and five big holes of 2.6 mm in diameter for the vapor discharge. The thickness is 10 mm and the diameter of the porous medium is 20 mm. As a result, the heat transfer experiments verify that utilizing the uni-directional porous cooling device strongly enhances the boiling/evaporation heat transfer and leads to the heat flux removal of over 10 MW/m~2 as well as being able to reduce the pumping power.