An experimental analysis of the impact of primary nozzle geometries on the ejector performance used in R141b ejector refrigerator

This paper gives an experimental discussion of the geometrical impact of the primary nozzle on the ejector performance in an R141b ejector refrigerator. Primary nozzle area ratio is varied to observe its effect on the ejector performance. Six primary nozzles are investigated experimentally. Four of them (D2.4M2.5, D2.8M2.5, D3.2M2.5, and D3.6M2.5) are designed with different throat diameters, but they have an identical nozzle area ratio. Two of them, D2.4M2.0 and D2.4M3.0, have an identical throat diameter, but they have different nozzle area ratio, resulting in a different nozzle exit Mach number. All nozzles are tested with one fixed geometry ejector at various operating conditions. Variations of the primary momentum caused by the change in primary nozzle throat and nozzle exit Mach number on the ejector performance is observed and discussed. The purpose is to determine the optimal primary nozzle geometries at given operating conditions. It is found that using a bigger nozzle throat, operated with lower generator temperature, is preferable. The primary nozzle exit Mach number should be as high as possible. It should also be designed to be consistent with the heat source's temperature for implementing the nozzle at the designed conditions. The primary nozzle exit diameter must be consistent with the mixing chamber used. Therefore, the minimum required generator temperature (Tgen-min) at various nozzle exit Mach numbers and the largest possible nozzle exit diameter for one particular ejector are provided for this present work. (C) 2016 Elsevier Ltd. All rights reserved.