Numerical and experimental study on the vapor-liquid distribution of loop heat pipe with varying density of working fluid

Loop heat pipes (LHPs) are effective passive heat transfer devices that are used in the thermal management systems for satellite payloads and electronic devices. The vapor-liquid distribution in the LHP determines the LHP's operating characteristics and heat transfer mechanism. This work developed a two-dimensional transient model for an LHP based on CFD methodology. The model includes a capillary force model and a phase change model, and considers the change in vapor and liquid densities during LHP operation. The steady-state vapor --liquid distribution in the condenser under different heat loads can be simulated. To validate the calculation results, a visualization experiment was conducted on the condenser. The simulation and the experimental results agree well. It was discovered that when the LHP works in steady-state conditions, the increase in vapor density and decrease in liquid density at high heat loads is a major cause for the the growth of liquid volume fraction in the condenser. When the condenser is entirely filled with liquid, the LHP fails to operate. The simulation model can be employed for theoretical research and design optimization of LHP.