Abstract
Loop Heat Pipe (LHP) performance strongly depends on the performance of a wick that is porous media inserted in an evaporator. In this paper, the visualization results of thermo-fluid behavior on the surface of the wick with microscopic infrared thermography were reported. In this study, 2 different samples that simulated a part of wick in the evaporator were used. The wicks were made by different two materials: polytetrafluoroethylene (PTFE) and stainless steel (SUS). The pore radii of PTFE wick and SUS wick are 1.2 μm and 22.5 μm. The difference of thermo-fluid behavior that was caused by the difference of material was investigated. These two materials include 4 different properties: pore radius, thermal conductivity, permeability and porosity. In order to investigate the effect of the thermal conductivity on wick’s operating mode, the phase diagram on the q-keff plane was made. Based on the temperature line profiles, two operating modes: mode of heat conduction and mode of convection were observed. The effective thermal conductivity of the porous media has strong effect on the operating modes. In addition, the difference of heat leak through the wick that was caused by the difference of the material was discussed.
Highlights
High efficiency heat transport devices are expected due to increase of power dissipated in electronicHow to cite this paper: Odagiri, K., Nishikawara, M. and Nagano, H. (2016) Microscale Infrared Observation of Liquid-Vapor Phase Change Process on the Surface of Porous Media for Loop Heat Pipe
loop heat pipe (LHP) is a two-phase heat transfer device using capillary action in a microscale porous structure that is called a wick inserted in the evaporator
The evaporator is a key component for enhancement of LHP performance because it strongly depends on its wick performance
Summary
High efficiency heat transport devices are expected due to increase of power dissipated in electronic. LHP is a two-phase heat transfer device using capillary action in a microscale porous structure that is called a wick inserted in the evaporator. In these components, the evaporator is a key component for enhancement of LHP performance because it strongly depends on its wick performance. The visual study of thermo-fluid behavior in the porous structure that has pore diameter that is smaller than dozens of microns is required. The experimental study of the difference of thermo-fluid behavior that is caused by the difference of wick material has not been performed yet. The purpose of this study is to reveal thermo-fluid behavior in the wick based on microscale infrared observation. The heat leak through the wick is estimated and the difference that is caused by the wick material is discussed
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