Vapor Compression Refrigeration Cycle for Electronics Cooling – Part I: Dynamic Modeling and Experimental Validation

This paper presents a first-principle lumped-parameter dynamic model and experimental validation of vapor compression cycles for electronics cooling. The model couples the dynamics of the heat exchangers with static empirical models for compressor and expansion valve. In contrast to past work on systems level modeling of refrigeration cycles, this paper focuses on imposed heat flux boundary condition, and the associated critical heat flux and critical vapor quality, in the evaporator. Using our vapor compression cycle testbed, we verify that the model prediction of the evaporator exit temperature and critical heat flux matches well with experimental measurements. The model is also used to search for operating conditions to enhance the critical heat flux. Experimental results show that at an undesired operating condition, even a small 5% change of heat flux could cause a wall temperature spike of over 100 °C, in contrast to 15 °C at a more advantageous operating conditions. For large heat flux transients, the onset of critical heat flux condition may be delayed, but its avoidance may require active refrigerant flow control.