Multistage Stirling Cycle Refrigeration Performance Mapping of the Ball SB235
T. Roberts, A. Razani
AFRL, Kirtland AFB, NM
Abstract
The performance mapping of a multistage Stirling cycle refrigeration system has been performed on the Ball Aerospace SB235 cryocooler by the Air Force Research Laboratory. The results are presented in terms of primitive variables such as temperature, work inputs, and cooling load supported. It is then restated in terms of composite variables such as available work (exergy) inputs, the individual and composite exergies of the cooling loads supported, and system efficiency. The results of this mapping when stated in terms of these composite variables shows that overall cooling performance follows discernible, distinct paths as external environmental conditions such as work input, rejection temperature, or imposed cooling load change. This composite performance is analogous to how cooling performance of a real single stage refrigerator is determined by its functional performance manifold with respect to these same environmental variables. Further analysis of this performance of the SB235 cryocooler suggests theoretical approaches to the question of how multistage Stirling refrigeration systems proportion available work to the discrete stages as a function of cooling load temperature, total available work input to the system, and rejection temperature. The data provided by this mapping would therefore form the basis for a theoretical first order model of how practical application environments alter the relative refrigeration performances of multistaged cold ends which now has to be empirically measured or predictively modeled using high order composite component models.
