Ejector Cooling

Numerical simulation of variable nozzle ejector of cooling system using R134a
Abstract
Cooling ejectors have been used in refrigeration applications for decades. Recent attempt researches are to minimize energy consumptions by harnessing renewable energy. This paper presents CFD model to study and evaluate the influence of exit nozzle position (NXP) on the ejector performance. The NXP can be controlled by the spindle feature which moves NXP forward or backward. Also the mass flow rate that enters the ejector is controlled by another spindle. By using both features two parameters can be controlled separately. From the simulation results, it is found that the optimal entrainment ratio Er can be obtained at certain position based on the operating

Rusly et al [5] studied and analysed couples of ejector designs that modelled by CFD techniques to resolve the flow dynamics in the ejector, the obtained results were validated with available experimental data. It was found that the maximum entrainment ratio happened in the ejector just before a shock occurs and the position of the nozzle is an important ejector design parameter. Allouche et al [6] studied the flow structure and the mixing process inside the steam ejector using CFD, it was found that no direct impact on the entrainment ratio from different condenser pressure. Varga et al [7] compared the CFD and experimental performance results for variable area ratio steam ejector, the variable geometry was done by a movable spindle in the primary nozzle inlet, the results were agreed well with average relative error of 8%. CFD predicted the entrainment ratio and secondary flow rate with accepted accuracy from 70% of the cases. Natthawut et al [8] employed the CFD technique to investigate the effect of the primary nozzle geometries on the performance of a steam ejector, two types of turbulences models k-ω-sst and relizable k-ϵ were compared with experimental values which obtained, it was found that k-ω-sst more accurate results, eight different nozzles were tested numerically, some parameters were observed and analysed such as the primary fluid pressure, Mach number, and mass flow rate, also it was found that the mixing chamber effected in the ejector performance. Varga et al [9]