Numerical simulation and analysis of heat leakage reduction in loop heat pipe with carbon fiber capillary wick
Abstract In this paper, a loop heat pipe (LHP) with a carbon fiber capillary wick was taken as the research object to study the steady state inside the LHP and validate the effectiveness of proposed improvements through CFD numerical simulations. A 3D model of the LHP was built and numerical simulations of steady state operation were conducted by ANSYS software. Through comparison of experiment and simulation results, heat leakage from the heated surface to the compensation chamber (CC) was identified as the major cause of failure in the feasibility experiment. The addition of a heat insulation layer on the contact surface between shells of the evaporator and the compensator was validated as an improvement in reducing heat leaking through the metal shells. The substitute of the copper plating by an alumina copper coating on surface of the carbon fiber capillary wick was proposed as an improvement to decrease the heat transferring through the capillary wick. The simulation shows that a silicon sheet with low thermal conductivity can increase the liquid volume fraction in the CC to 23% while an yttria stabilized zirconia (YSZ) heat insulation layer can raise the figure to 74% According to simulation results, the combination of YSZ layer and alumina copper coating can realize a temperature drop of 5.7 K comparing with the combination of silicon sheet and copper plating. The optimized experiment indicates that the use of the heat insulation layers improves stability of operation and increases bearing heat load of the LHP. The dependability of simulation results and the rationality of experimental error were proved by comparing results of experiment and simulation under the same operation conditions.