Characteristics of phase-change heat transfer in a capillary evaporator based on microscale infrared/visible observation

In this study, the characteristic of liquid-vapor interface behavior in a capillary evaporator of loop heat pipes (LHPs) is studied experimentally and theoretically. The behavior of a phase-change heat transfer at the surface of a fine porous medium that is called a wick, is evaluated using microscopic infrared camera and microscope. Four distinct samples made using four different materials (polytetrafluoroethylene and stainless steel (SS1.0 mu m, SS4.5 mu m, SS22 mu m)) were used to simulate a part of the wick used in the evaporator. The changes in a heat transfer coefficient were caused by three types of liquid-vapor interface behaviors. In the analysis, a one-dimensional model of the liquid-vapor interface behavior in the wick is proposed based on thin liquid film evaporation theory. The predicted heat transfer coefficient was in good agreement with the experimental data. (C) 2018 Elsevier Ltd. All rights reserved.