Study on the behaviours of a controllable loop thermosyphon used in the temperature control of a fresh food compartment

The loop thermosyphon with active heat transfer control capability is a promising solution for the temperature management of the fresh food compartment of cool-storage refrigerators or other precise temperature control devices. However, the frequently start-stop operating mode of the loop thermosyphon has not received enough attention, the active temperature management behaviours of the loop thermosyphon still requires further investigation. In this study, a controllable loop thermosyphon (CLT) used in the temperature control of a fresh food compartment is developed. the start-stop of the CLT is controlled by the temperature controller with the assistance of two solenoid valves. The performances of CLT in long-term and start-stop operating modes are tested. The CLT with 35% filling ratio present highest heat transfer rate, reliable heat transfer capability, and stability for different temperatures in the fresh food compartment. Based on this filling ratio, the heat transfer rate of CLT remains higher than 40 W during the long-term operating test. The fitted equivalent heat transfer resistance increases sharply at first and then gradually decreases to 0.59 °C/W as the temperature of the fresh food compartment drops to 0 °C. When the CLT operates in the start-stop mode, the start-stop cycle decreases from 39.4 min to 27.2 min and the operating ratio increases from 12.6% to 53.7% as the temperature of the fresh food compartment rises from 2 °C to 8 °C. The results demonstrate that the precise temperature management capability of CLT is qualified as a novel temperature management device for the use in cool-storage refrigerators, as well as for other applications.