Ground Simulation of High Altitude Test of Turbo-Refrigeration Cycle

Abstract

This study proposes a new test approach for a ram air-driven turbo-refrigeration system. The flight performance of the air cycle turbo-refrigerator is indirectly verified through ground tests under various flight conditions, and the actual altitude performance is predicted through dimensional analysis and similarity based on the ground test results. In addition, correction of the Reynolds number is also considered for adequate prediction of performance. This study develops a turbo-refrigerator that consists of a radial turbine and a centrifugal compressor. As this simple system drives the reverse Brayton cycle, it acts as a refrigerator that relieves the heat load. Although the ram air and exhaust conditions are usually simulated in high altitude test facilities, they are very costly and not suitable for prototype development, which often demands requirement and specification changes. The proposed system is designed to deliver a cooling capacity over 2kW through the heat exchanger at a Mach number of 0.8 and altitude up to 10 km. As a result of current study, the proposed test approach predicts that air cycle turbo-refrigeration system yields sufficient cooling capacity to comply with the requirements for the primary mission flight envelope under the hot day condition, despite slight performance degradation at high altitudes.