Numerical study on the heat transfer characteristics of oscillating flow in cryogenic regenerators

The heat transfer characteristics of oscillating flow in regenerator have significant impacts on the system performance of regenerative cryocoolers such as pulse tube, Stirling and G-M type cryocoolers. In this paper, the hydrodynamics and heat transfer in porous media featuring periodically configured arrays of cylinders are simulated under periodically oscillating flow conditions. The effects of operating parameters including working frequency, velocity amplitude and location on the heat transfer coefficient are evaluated. The simulation results reveal that the Nusselt number is significantly different between steady and oscillating flow conditions with the magnitude strongly depending on the oscillation frequency and velocity amplitude. A correlation for the cycle averaged Nusselt number is proposed, which yields deviations of 7% from the simulation results of the oscillating flow in the cylinder array.