Numerical Analysis of a Split-Type Free-Piston Stirling Cryocooler for Space Application

Abstract

Abstract. In space applications, cooling of infrared (IR) sensors is essential because they can easily overheat from internal heat generation and radiative heat from their surroundings. Miniature free-piston Stirling cryocoolers, which use helium as working fluid, can produce a cooling effect ranging from 0.25 W to 5 W at 80 K, making them well-suited for cooling IR sensors. In this study, a miniature split-type free-piston Stirling cryocooler (SFPSC) was designed and numerically investigated using a third-order design software sage. The designed cryocooler can produce a cooling effect of 1.27 W at 80 K, resulting in a coefficient of performance (COP) of 0.03256. A comprehensive parametric analysis was performed to study the impact of key operating and geometric parameters on SFPSC performance. An available energy loss analysis of the cryocooler reveals that 43.1% of the total energy loss occurs in the split tube, due to high viscous dissipation as fluid flows through a narrow passage. Additionally, an investigation was conducted to examine the effects of regenerator mesh number and porosity on cooling capacity, COP, and various losses in the SFPSC. For a constant porosity, increasing the mesh number reduced thermal losses but increased the pressure drop. Conversely, for a constant mesh number, increasing the porosity decreased the pressure drop but increased thermal losses. The outcomes of this study provide new insights into the performance behavior and dominant loss mechanisms of SFPSC, highlighting important regenerator design tradeoffs and offering guidelines for optimizing the cooler for IR-sensor applications.