Experimental and Predicted Performance of the BEI Mini-Linear Cooler

Abstract

BEI is a manufacturer of Stirling-cycle cryocoolers based on the concept of clearance seal, pneumatically driven displacer and linear drive motors. Several cooler models are available covering refrigeration requirements ranging from 150 mW to 5.0 Watts of cooling at 78 K. This paper describes a computer simulation model, herein referred to as Hybrid Refrigeration Model (HRM), that was developed for the design of BEI coolers. The BEI computer model uses a novel technique that greatly reduces computation time without compromise in accuracy.

The hybrid model is used at BEI for the design of both Stirling and Pulse-Tube refrigerators. The model is similar, to a third order model described in the literature as the Stirling Refrigerator Performance Model (SRPM), that has been extensively validated against various Stirling and Pulse Tube designs from different manufacturers. Although very accurate in its prediction, the SRPM suffers a major shortcoming in its long run time. The Hybrid Refrigeration Model, on the other hand, uses a third order approach in calculating mass flows and pressure drops within the refrigerator while the losses are imposed using the second order analysis. This approach has provided an accurate tool for performance prediction with fast turnaround. An example of the use of this computer model is provided in this paper with the parameters of the BEI Mini-linear cooler. The performance of the cooler is discussed, in particular, the effects of the regenerator material, configuration and operating conditions.