Numerical simulation and design of ejector for solar air conditioning systems

In this thesis a generalized ejector for solar air conditioning system was successfully developed by using FLUENT. A 1-D analysis for ejector is carried out in this work. It revealed the influence of operating pressures and ejector geometries on the flow structure and the performance of an ejector air conditioning system using ammonia vapour as the working fluid. The primary nozzle geometries parameter was varied as 2.90 mm2, 2.93 mm2 and 2.96 mm2. For a given ejector, there exists an optimum primary fluid pressure at which maximum entrainment ratio is obtained. Entrainment ratio is decreased by increasing the primary fluid pressure and entrainment ratio is increased by decreasing the discharge pressure. The best performance was obtained by operating condition Pg=0.4 MPa, Tg=100℃, Pe=0.04 MPa, Te=4℃, Pc=0.06 MPa, and Tc=28℃ with primary nozzle geometry of 2.90 mm2 gives the highest entrainment ratio for better performance. A 2D axisymmetric, ideal gas model was developed to calculate the flow in the ejector air conditioning system. Predictions at the operating conditions in the ejector air conditioning system were discussed to obtain the ejector performance in the double choking or critical mode condition and variable operating condition. The effects on the primary fluid pressure and Mach number were observed and analyzed. It was found that shock’s position of the mixed fluid and the expansion diameter of the primary fluid supersonic stream within the mixing chamber played a very important role in the ejector performance. The critical back pressure Pc^* on the different ejector throat diameters A3 have obtained. When the ejector throat diameter A3 is larger, the critical back pressure (Pc^* ) is lower. When the ejector throat diameter A3 is smaller, the critical back pressure Pc^* is higher. When the ejector throat diameter A3 < 12.7 mm^2, ejector can’t work even if the back pressure is very low. The change of the ejector performance is caused by the change of shock wave. Which is the result of the change of ejector throat diameter A3.