A validated numerical-experimental design methodology for a movable supersonic ejector compressor for waste-heat recovery

Abstract

The aim of this paper is to develop the technical knowledge, especially the optimum geometries, for the design and manufacturing of a supersonic gas-gas ejecto r for a waste heat driven vehicle cooling system. Although several studies have been performed to inves tigate the effects of geometrical configurations of gas-gas ejectors, a progressive design methodology of an ejector compressor for application to a vehicle cooling system has not yet been descr ibed. First, an analytical model for calculation of the ejector optimum geometry for a wide range of opera ting conditions is devel oped, using R134a as the working fluid with a rated cooling capacity of 2.5 kW. The maximum values of entrainment ratio ( ߱ ) have been estimated by correlation of the main parameters in a non-dimens ional form. The optimum values of nozzle throat diameter ( ݀ ௡௧ ) and mixing chamber diameter ( ݀ ௠௖ ) thus obtained are used as a starting point for the CFD optimization covering a wide range of geometrical configurations. To assess the effect of various dimensional quantities, an optimization technique has been proposed for calculation of the most efficient geometry of the target ejector for manufacturing. Using a vehicle cooling system as a test case, the final optimized dimensions are reported and discussed. An e xperimental validation confirms the CFD results and the ejector performance with a normalized deviati on of 5% between observed and simulated results, demonstrating that the methodology is a valid ejector design tool for a wide range of applications.