Steady-state Operating Characteristics Analysis of Loop Heat Pipes with Flat-Plate Evaporator

A mathematical model of gravity-assisted flat loop heat pipe has been established, based on mass conservation, energy balance, combining pressure-temperature and heat & mass transfer relations. The effects of gravity, heat sink and ambient temperature on steady-state performance of the loop heat pipe were comprehensively investigated. The modeling results show that there exist two driving modes: gravity-driven mode and capillary-gravity co-driven mode when plate loop heat pipes operate under gravity-assisted condition. Besides, a critical heat flux has been found between the gravity-driven mode and the co-driven mode. The condensate capacity of heat sink and ambient temperature to the heat regenerative ability of the liquid line affect the variable heat-conductance zone and constant heat-conductance zone. These findings are beneficial to the comprehensive understanding of the operating characteristics, which can guide the design and optimization of the flat loop heat pipes.