This paper proposes a theoretical model to investigate the thermal performance of a cold storage system with multi-loop wickless heat pipes. The cold storage system utilizes the superior heat transfer characteristics of heat pipe and eliminates drawbacks found in the conventional thermal storage tank. A modified RC circuit model to determine the thermal characteristics of the cold storage system has been developed. Experimental investigations are then conducted to study the cold storage thermal performance in an experimental system with the ratio of distance between heat pipes to outer diameter of heat pipe W/D = 2. Different heat transfer mechanisms, including nucleate boiling, geyser boiling, and natural convection, are identified in different experimental systems with various liquid fills. This paper probes the effect of the fill level on cold storage rate and cumulative cold storage quantity. Comparisons of this theory with experimental data show good agreements in the nucleate boiling stage of cold storage process.

Units: SI