Nusselt number correction for stacked wire mesh considering finite heat capacity below 50 K

Abstract

In regenerative cooling systems, the heat transfer characteristics of regenerators employing stacked wire mesh are critically important. Numerous experimental and numerical investigations have been conducted to characterize the Nusselt number of regenerators, focusing on room temperature conditions where the solid heat capacity is sufficiently large compared to that of the gas . In this study, the #400 stainless steel mesh is simulated in three dimensions at pore scale to investigate the Nusselt number across various flow conditions, considering both unidirectional and oscillating flow. Under unidirectional flow, the heat transfer characteristics below 77 K are studied. Considering the influence of finite heat capacity of stainless steel, a modified Nusselt number formula applicable to the 50 K to 20 K range is generalized. Subsequently, the heat transfer characteristics under oscillating flow, including different frequencies and pressure ratios, are investigated. The results provide further evidence supporting the similarity of Nusselt numbers between oscillating and unidirectional flow. This study provides a deeper insight into the heat transfer characteristics of wire mesh regenerators at low temperatures. Meanwhile, the forementioned modified coefficient can be used for better regenerator simulations.