Transition of Refrigeration Thermodynamic Analysis From Component to a Radar Power System

Abstract

Preliminary feasibility studies based on breakeven refrigeration thermodynamics, have been conducted for candidate power conditioning components in a transportable radar power system (Donovan, B.D. et al., 1995 “Effects of Refrigeration in a Transportable Cryogenic Aerospace Application,” Proc. 30th IECEC, Vol. 1, pp. 473–478; Ramalingam, M. et al., 1996 “Systems Analysis for a Cryogenic Aerospace Terrestrial Radar Power System,” Proc. 31st IECEC, Vol. 1). The analysis based on breakeven refrigeration thermodynamics revealed that in the case of a general switching device such as a power MOSFET, it would be more beneficial to operate it at 150 to 220 K, using a Stirling cycle-based cryocooler. The overall system efficiency was jeopardized by way of large input power requirements to cool small heat loads at lower temperatures, while the performance of the device itself suffered at higher temperatures. The break-even refrigeration thermodynamic analysis was also applied to multilayer ceramic capacitors at cryogenic temperatures. It was found that in order to avoid a power penalty for cooling the capacitor to 77 K, the cryocooled equivalent series resistance (ESR) value would have to be a factor of 40 lower than that of a conventional capacitor ESR value if using a Gifford-McMahon (GM) cooling cycle. A factor of 12 better improvement in ESR is required for a yet-to-be-developed more efficient Stirling cycle. In this paper, this break-even thermodynamic analytical concept was then partially extended from the component level to the radar power system level. The entire power system was sized based on several combinations of cryocooled generators, power conditioning, and antenna equipment. The analysis revealed that even though the radar output could potentially be increased two-to threefold by the introduction of cryocooled technologies, the sizes of the coolers begin to negate these advantages. Several power systems were evaluated with reference to a common figure-of-merit to arrive at an optimum configuration. [S0195-0738(00)00803-7]