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2. PHD Thesis / Tesis PHD
3. Solar Energy Research Institute / Institut Penyelidikan Tenaga Suria (SERI)

Title:	Performance evaluation of variable ejector in a hybrid air conditioning system
Authors:	Bashir Rahuma Elhub (P69921)
Supervisor:	Sohif Mat, Prof. Dr.
Keywords:	Refrigeration and refrigerating machinery Air conditioning Universiti Kebangsaan Malaysia -- Dissertations Dissertations, Academic -- Malaysia
Issue Date:	3-Oct-2018
Description:	Air conditioning equipment consumes considerable amount of energy and is estimated at about 37% of the world electricity consumption in the developed countries. The environmental benefits of using ejector cooling cycle is to reduce the carbon dioxide emissions by reducing the global warming impact and using friendly refrigerants. Ejector system is one of the most promising method for air conditioning. Ejector reduces the electricity consumption by replacing the mechanical compressor for compression of the refrigerant. The major challenge of ejector cooling system is the low performance. The reason is that the entrainment ratio between secondary flow to the primary flow and the optimum design of the geometry at different operating conditions. The main objective of this study is to enhance the Coefficient of Performance of the ejector and evaluate the variable cooling ejector experimentally. A 2 hp ejector cooling capacity have been studied numerically and experimentally. The variable ejector has two variables which can be controlled simultaneously was designed and fabricated. It was tested in a hybrid conventional–ejector air conditioning system. A computer model of the ejector geometry was developed by using ANSYS fluent 17.2. In the model the solutions to basic conservation equations, including the influence of shockwave in the ejector diffuser has been obtained. Simulation on the ejector were used to predict the relationship of six different parameters:(nozzle exit position, inlet primary pressure, inlet secondary pressure, inlet primary temperature, inlet secondary temperature, and outlet pressure) with optimization towards entrainment ratio. The significance of movable ejector has been used to determine the best operating parameters with varying environmental energy and effect on the inlet pressure, outlet pressure and temperatures. Sensitivity analysis was conducted to determine which of the parameters give the highest impact to entrainment ratio. Four of the parameters have been inversely proportional towards entrainment ratio (nozzle exit position, inlet primary pressure inlet secondary temperature and outlet pressure) while the other two (inlet secondary pressure, inlet primary temperature) vice versa. Nevertheless, outlet pressure has been the most sensitive parameter as it affects several important factors: location of mixing, location of choke flow and flow distribution inside the converging diverging nozzle. The optimum point for nozzle exit position is approximately 3 mm for this geometry configuration and the entrainment ratio was found to be around 1.2823. For nozzle exit position more than 4mm, the effect of outlet pressure has been more dominant thus creating back flow inside the nozzle. However, most of the parameters are affecting each other and thus Multi Objective Genetic Algorithm has been employed. The Coefficient of Performance affected by the back pressure, the optimum entrainment ratio was found when nozzle exit position around 4mm from the mixing chamber and primary pressure between (17-23 bar). Condenser pressure also has the most influence with the Coefficient of Performance was obtained at the optimum when the condenser temperature ranged between (28- 42 °C) and the primary pressure at 17 bar, nozzle exit position at 4mm. The performance of the system was affected by condenser load. The optimum Coefficient of Performance was obtained 0.99 when condenser load was at 4 kW. The experimental results obtained showed that the electricity consumption could be reduced 5% - 8% when the ejector operates at optimum performance showed good agreement with the numerical simulation obtained from Engineering Equation Solver software and computational fluid dynamics fluent software.,Ph.D.
Pages:	246
Call Number:	TP492.E375 2018 3 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Solar Energy Research Institute / Institut Penyelidikan Tenaga Suria (SERI)

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