Numerical study on coupling phase change heat transfer performance of solar dish collector

In solar dish collector system, the heat transfer process is a typical coupling heat transfer problem, where the heat conduction, radiation heat transfer, convection heat transfer and phase change heat transfer are coexisting. In the present paper, a coupling model for Monte Carlo Ray Trace Method (MCRTM) and Finite Volume Method (FVM) was established to study the coupling heat transfer problem. Firstly, based on MCRTM, the non-uniform 3D heat flux distributions on the solar dish receiver inner surface were obtained. Then the non-uniform heat flux distribution is used as the boundary condition to simulate the phase change and convection heat transfer process inside the heat transfer tube. The effects of the non-uniform heat flux distribution on temperature field in phase change material (PCM) were examined. The results show that the non-uniform heat flux on the tube surface will result in seriously non-uniform temperature distribution in PCM. Then the optimization analyses for the temperature distribution were performed according to the convection heat transfer process and heat conduction process respectively. The results show that in the studied conditions, when heat transfer fluid (HTF) velocity increases from 10m/s to 25m/s, the maximum temperature difference in PCM will decrease from 781.2K to 497.8K, which reduces about 36.3%. However, it will cause the heat storage capacity and HTF outlet temperature decrease. When the thermal conductivity increases from 3.8Wm^-1K^-1 to 19.0Wm^-1K^-1, the maximum temperature difference will decrease from 781.2K to 409.5K, which reduces about 47.6%. And it will not result in HTF outlet temperature and heat storage capacity decreasing. So, enhancing the PCM thermal conductivity is an efficient method to achieve more uniform temperature distribution in PCM.