Thermal analysis of a conceptual loop heat pipe for solar central receivers

This study presents a novel loop heat pipe central receiver for the solar power tower (SPT) plant. For the first study, the evaporator section of the proposed receiver is simulated by a three-dimensional numerical model to study the flow, heat transfer and the evaporation phenomenon of the working fluid. In addition, effects of the outlet boundary pressure at the vapor groove and the solar irradiation heat flux on the absorbing surface are analyzed. The results show that most of the working fluid vaporizes at the liquid/vapor interface close to the casing. The heat transferred from the casing to the vapor working fluid is negligible, and thus the vapor temperature in the groove can be assumed to be constant in simulating the whole loop heat pipe central receiver. A lower temperature difference between the liquid/vapor interface and the compensation chamber is beneficial for obtaining more heat energy transferred to the vapor working fluid. It is also found that the evaporation heat transfer coefficient changes obviously with the absorbed solar heat flux. The findings of present work can be used as a reference to the modelling and design of the whole loop heat pipe central receiver in the next step.