Preliminary study on variable conductance loop thermosyphons

Given that loop thermosyphons are widely used as simple and high-efficiency heat transfer devices, their passive heat transfer performance has attracted considerable research interest. The capability of loop thermosyphons for active heat transfer adjustment can potentially improve the precision and efficiency of heat and temperature management in many fields, but has not received much attention. A variable conductance loop thermosyphon (VCLT) is developed in this study. Heat transfer is precisely adjusted by actively regulating the internal flow resistance of the working fluid. The performance of VCLT under variable flow resistances is tested. The boundary conditions are set to those of a novel cool-storage refrigerator, wherein temperature control directly affects the freshness of stored food. VCLT behaviors under static and dynamic adjustment modes are also examined with the working fluid R134a. The maximum ratio of heat transfer adjustment is approximately 85%, when decreases the mass flow rate from 1.67 g/s to 0.21 g/s with increasing the equivalent thermal resistance from 0.0074 K/W to 0.54 K/W. Finally, the performance is verified with R404a, R407a and R410a. Results demonstrate that VCLT is an efficient and low-cost temperature adjustment device for refrigerators and other applications that require precise temperature control.