Research on Coupling Performance of Heat Transfer and Throttling of Microchannel J-T Effect Cryocoolers

Abstract To solve the shortcomings of small cooling capacity of the current Joule-Thomson (J-T) cryocooler, a multi-layer microchannel J-T cryocooler is designed and fabricated by printed circuit board technology. The characteristic of the cryocooler is that there exists heat transfer while throttling. The coupling effect of heat transfer and throttling affects the overall performance of cryocooler. Therefore, the steady-state model was established for each part of the cryocooler. The P-h diagram of N 2 was calculated by the model. Considering the variation of J-T coefficient ( μ jt ) in the process, the coupling performance of heat transfer and throttling in the J-T cryocooler were analyzed. A new parameter, J-T efficiency ( η jt ), was proposed to evaluate the J-T effect. Additionally, according to the dependence of μ jt with temperature and pressure, the refrigeration performance of the cryocooler under different working conditions was simulated. The results show that the heat transfer in the throttle can enhance the throttling effect. When the inlet temperature is 285.0K and the inlet pressure increases to 18.00MPa, the N 2 temperature at the cold end reaches 116.3K, and the gross cooling capacity is 4.55W. When the inlet pressure is 6.00MPa and the inlet temperature reduces to 195.0K, the temperature at the cold end can reach to the saturated temperature of 103.2K, and the maximum gross cooling capacity is 7.68W. For the two groups of working conditions, the heat transfer in the throttle can enhance the J-T effect. η jt reaches 95.87% and 94.76%, the proportion of temperature drop caused by J-T effect is 56.10% and 68.03% of the total temperature drops, respectively. Finally, the variation laws of inlet temperature and η jt are analyzed when N 2 reaches saturated temperature under different pressures to guide the selection of inlet parameters.