Quantitative evaluation of a free piston Stirling cooler performance based on a dimensionless analysis method and experimental results

Free piston Stirling cooler (FPSC), which operates on the reversed-Stirling cycle, is characterized by high efficiency, long lifespan, and compact structure. This study employs a dimensionless analysis method to quantitatively evaluate FPSC performance across various scales, focusing on the effects of key parameters on the coefficient of performance (COP), entropy generation, and response time. Comparison between experimental and simulation results indicates that the piston displacement error is below 5%, while the cold-end temperature deviation is limited to 1.39%. Results indicate that doubling the dimensionless mover mass decreases the COP by 23.08%. Conversely, doubling the cylinder diameter-to-stroke ratio increases the COP by approximately 95.00% and reduces dimensionless entropy generation by 66.69%. Increasing the dimensionless leaf spring stiffness to 2.5 times its initial value decreases the COP of 10.77%. A 37.5% increase in the dimensionless damping coefficient decreases the COP by 25.81% and reduces dimensionless entropy generation by 23.96%. When the dimensionless cooling target temperature increases by approximately 66.7%, the COP improves, the required dimensionless input energy decreases by 84.21%, and the dimensionless response time shortens by 83.22%, although the rate of reduction gradually slows. These findings provide valuable theoretical guidance for optimizing FPSC performance and guiding the selection of critical design parameters.