Numerical investigation on the influence of radial thermal conduction in a co-axial pulse tube cooler

Abstract

A co-axial pulse tube cooler, whose regenerator normally surrounds the pulse tube, has the most compact structure. Internal radial thermal conduction may occur between the regenerator and pulse tube due to the temperature mismatch at the same axial location. Theoretical analysis indicates that radial transferred heat flow from pulse tube to regenerator can increase the cooling power, while the opposite radial heat flow which flows from regenerator to pulse tube would decrease the cooling power. Then CFD models with and without radial thermal conduction based on a practical single-stage pulse tube cooler have been conducted to further analyze the mechanism and effect. Simulation results show that after introducing radial thermal conduction, the maximum temperature difference between the gas in regenerator and pulse tube is reduced from 25 K to below 10 K, and cooling power is reduced by 5.8% as a result of the time-averaged radial heat flow from regenerator to pulse tube. The influence of thermal conductivity of the coupled wall between regenerator and pulse tube is also discussed. This study provides a better understanding on the radial heat thermal conduction in a single stage co-axial pulse tube cooler, which sets the basis for optimizing the geometrical arrangement of co-axial pulse tube coolers.