TITLE:
Microscale Infrared Observation of Liquid-Vapor Phase Change Process on the Surface of Porous Media for Loop Heat Pipe
AUTHORS:
Kimihide Odagiri, Masahito Nishikawara, Hosei Nagano
KEYWORDS:
Evaporator, Liquid-Vapor Phase Change, Loop Heat Pipe, Microscale Infrared Observation, Porous Media
JOURNAL NAME:
Journal of Electronics Cooling and Thermal Control,
Vol.6 No.2,
June
2,
2016
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.