Numerical study of the regenerator for a miniature Stirling cryocooler using the local thermal equilibrium (LTE) and the local thermal nonequilibrium (LTNE) models

Abstract

Miniature Stirling cryocooler is widely used for cooling of IR detectors. In the present study, a numerical investigation is carried out on a regenerator for a miniature Stirling cryocooler, with Helium as the working fluid. The regenerator region made up of a stack of wire meshes is modelled as a porous medium. For modelling heat transfer in the regenerator, both the local thermal equilibrium (LTE) and the local thermal nonequilibrium (LTNE) models are used. The reciprocating motion of the compressor piston and the cold tip has been modelled with dynamic meshing. The thermo-physical properties of the working fluid and the wire mesh are considered to be varying with temperature. The maximum difference in the temperature obtained from the LTE and the LTNE models vary from +4% to −8% over the full length of the cryocooler at t = 40 s. From the present study, it was identified that the LTE and the LTNE models predict the overall temperature variation along the regenerator closely. However, for capturing accurate heat transfer characteristics, including thermal saturation, the LTNE model has to be used, even though it is computationally expensive.