Investigation of gravitational effects in pulse tube cryocoolers using 3-D CFD

Abstract

Investigation of Gravitational Effects in Pulse TubeCryocoolers Using 3-D CFD Abstract. Stirling-type pulse tube cryocoolers (PTC) are often selected for cryogenic cooling applications for their robustness and mechanical simplicity, having no moving parts at the cold end of the cooler. Originally designed for space applications, increased terrestrial use in tactical applications as well as ground testing of space systems has revealed that some PTCs exhibit sensitivity to gravitational orientation, often losing significant cooling performance unless situated with the cold end pointing downward. Previous investigations have indicated that some coolers exhibit sensitivity while others do not; however, a reliable method of predicting the level of sensitivity during the design process has not been developed. We have utilized 3-D computational fluid dynamics (CFD) to predict the percent of cooling capacity lost as a result of off-axis operation. The computational model has been validated experimentally on a number of coolers to enhance confidence in the method used.

Numerical investigation on non-linear streaming effects in a two-stage coaxial pulse tube cryocooler

“…These boundary layers can impede the gas flow, leading to an increase in gas resistance and decrease in heat transfer efficiency. [16][17][18] However, the physical visualization of such oscillating phenomena is quite impossible as it happens in a stainless steel pipe. This needs specialized neutron imaging visualization techniques to accurately detect those streamlines.…”