Thermal optimization of inter-stage heat exchangers distribution in a three-stage cascading pulse tube cooler

The cascading pulse tube cooler (CPTC) with a transmission tube has the advantages of high efficiency by energy recovery and high reliability by introducing no extra moving parts to the system and can provide cooling capacity at different cooling temperatures. The efficiency of CPTC still needs further improvement to meet the requirement of superconducting cooling and other applications. As there are 3 heat exchangers (HXs) in each stage of CPTC, it's essential to analyze the losses inside the HXs and optimize the distribution of HXs in CPTC. In this paper, the numerical simulation is conducted to analyze the temperature distribution and pressure drop of different arrangements of hot-end HX (HHXs) and transmission tubes. Simulation results show that the acoustic loss decreases from 10.36 W to 5.17 W when first stage HHX (HHX I) is eliminated from the original CPTC for the same working condition. Experimental tests of a three-stage CPTC are carried out to verify the optimal distribution of the HHXs, the cooling capacity of the three-stage CPTC increases from 249.6 W (original) to 273.5 W (optimized) at 233 K with an input power of 500 W, and the efficiency is improved by 9.46 %. Moreover, the efficiency of the three-stage CPTC with the optimized distribution of the HHXs is improved by 50.7 % at 233 K when compared with the single-stage PTC. The pressure amplitude at the inlet of each stage also increases. The results verify the optimization method for the distribution of IHXs and further confirm that CPTC improves the efficiency of PTC.