Research on the refrigerant column height in the downcomer of a two-phase loop thermosyphon

A two-phase loop thermosyphon (TPLT) is a highly efficient heat transfer device. It is a type of gravity-assisted heat pipe system. Therefore, there is a high refrigerant column height in the downcomer that supplies the driving force for the TPLT system. This study focused on the investigation of factors that influence the refrigerant column height in the downcomer of a TPLT system through an experiment and a numerical simulation. These factors were identified as the flow resistance, increased working pressure, and amount of liquid phase flow in the two-phase flow. In addition, the effect of the condenser height was considered. The extreme situation in which the condenser was filled with liquid refrigerant was analyzed through an experiment. The results indicated that a high refrigerant column height would occupy part of the condenser space and decrease the performance of the TPLT. In practical applications, the relationship between the condenser and refrigerant column height should be considered. These influencing factors of the column height in the downcomer should be considered when deciding the geometric parameters and filling ratio of a TPLT system.