Two-phase loop thermosyphon is promising in free cooling of data center, base station, and other industrial buildings with high temperature heat source. The large-scale circulation loop of its natural phase-change cycle is complex with high internal flow resistance in these context and thus is hardly related to the thermodynamic properties of working medium, which has yet to be revealed in detail. In this study, a distributed steady-state model was implemented to verify the heat transfer performance of a two-phase loop thermosyphon with different working mediums under high internal flow resistance for building air-conditioning. Simulative study shows that the behaviors of R744 and R410A are relatively superior, and R744 is outstanding at the extreme high thermal resistance condition. The operating states with different mixed refrigerants are more stable in comparison with pure refrigerants. Eco-friendly mixed refrigerants with low cost and high safety are alternative selections for two-phase loop thermosyphon in building applications.
Keywords thermosyphon, heat transfer, building cooling, refrigerant