Experimental study of a cascade pulse tube cryocooler with a displacer

Recovering the expansion power in pulse tube cryocooler is of great utility in improving cooling efficiency. Using a second-stage cooler after a primary cooler to produce extra cooling power is an effective way especially when the cooling temperature is not very low. In the configuration, the two coolers are connected by a displacer which is used as a phase shifter. In this paper, experimental investigations were conducted to study this system. Firstly, the performance of the overall system and separated cooler was respectively presented. To better understand the displacer, phase relation, mechanical resistance and displacement were then clarified. In addition, the power consumption distribution of the cascade cryocooler was discussed. Finally, both numerical and experimental comparisons were made on the displacer-type and tube-type cryocooler. The experimental results show that the displacer-type cryocooler has superior performance due to the better phase-modulation capability and less power loss. With the input electric power of 1.9 kW and cooling temperature of 130 K, the overall system achieved a cooling power of 371 W and a relative Carnot efficiency of 24.5%.