Numerical Investigations about Flow Resistance Values for Stirling Type Pulse Tube Cryocooler

Abstract

Pulse tube cryocoolers are extensively used for space application because of simplicity and reliability in operation. Many researchers have attempted the numerical analysis of the oscillatory flow inside the cryocooler, however, the precise predictions of the exact behavior of the gas inside the cryocooler using CFD has not yet been reported. While performing the CFD analysis of cryocooler, the values of inertial and viscous resistance coefficients play vital role and highly contributes to the pressure drop taking place in porous media. The prime objective of present work is to analyze the effect of these resistance values on performance of cryocooler. A single stage Stirling type pulse tube cryocooler model from literature is employed to perform the CFD analysis and the results obtained from the analysis are validated to ensure that methodology used for analysis is correct. The resistance values mentioned in the literature are applicable for steady and unidirectional flows. The model is further modified for the values of resistances for oscillating flow at room temperature and oscillating flow at cryogenic temperature. It is observed that performance predictions for oscillating flow at cryogenic temperature resistance values yields substantially lower temperature than all other cases. As experimental validation of this model is still not reported in literature, the reliability of accurate resistance values is not confirmed. Hence, another model of single stage Stirling type pulse tube cryocooler from literature is numerically analyzed for various operating conditions and is compared with its experimental performance, and found to be in fair agreement.