International Journal of Engineering, Management & Sciences (IJEMS) ISSN-2348 –3733, Volume-2, Issue-5, May 2015
Theoretical Performance Analysis of Vapour Jet Ejector for R 134a Sonia Rani, Gulshan Sachdeva Abstract— In the present paper performance of refrigerant R134a is discussed throughout an ejector for low temperature heat source for refrigeration and air–conditioning applications. The proposed system performance has been compared with Carnot cycle working at same operating conditions with influence of condenser, generator, and evaporator temperature on performance of Vapour Jet Refrigeration (VJR) system. Furthermore, the effect of ejector efficiency also discussed at constant operating conditions. The design conditions were evaporator temperature (5-15˚C), condenser temperature (30-45˚C) and generator temperature (75-80˚C). For calculation purpose mathematical equations are developed and simulation results are obtained with EES (Engineering Equation Solver). The present results depicts that the performance of the ejector highly depend on operating conditions on the performance of ejector system. Index Terms—Ejector, R134a, Refrigeration.
Mathematics, Performance,
I. INTRODUCTION Refrigeration and air conditioning is essential extensively in world requirement of different applications like hotels, buildings, hospitals, manufacturing of ice, domestic refrigerators, deep freezers, automobiles, heating and ventilation. Refrigeration is a process of maintains of system temperature below than environment temperature by providing continues supply of energy in form of electricity. Generally vapour compression refrigeration system (VCRS) is employed for meet refrigeration purposes in addition to abundant amount of electricity providing to mechanical compressor [1]. As we know to meet huge amount of electricity demand fossils fuels are used for energy generation. By burning coal and fossils fuels we meet mainly two problems as follows: One is emission of CO2 gas which is dangerous for environment. The other is increasing global warming potential due to emission of chlorine atom from refrigerants. As a result, the European commission Regulation 2037/2000, installed on 1 October 2000, a program to control all the ozone depleting materials and all HCFCs (hydro chlorofluorocarbons) will be forbidden by 2015 [2]. One Manuscript received February 20, 2015. Sonia Rani , School of Renewable Energy and Efficiency, National Institute of Technology, Kurukshetra, India, Gulshan Sachdeva, Mechanical Engineering Department, National Institute of Technology, Kurukshetra, India,
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solution is to overcome this problem adoption of clean energy. However, we can use waste heat or solar heat for refrigeration and air conditioning. For utilizing of solar heat or waste heat Eejector air conditioning is attractive choice. Advantage of elimination of mechanical compressor no moving part except pump makes it more reliable in addition to reduced maintenance cost. In the present study Munday and Bagster theory is use according to which assumption of two discrete streams was considered [3]. The motive stream flow through primary nozzle and suction stream flow through secondary nozzle attains mixing of both fluids in mixing section at constant pressure. Immediate mixing shock wave generate results to subsonic velocity of mixed stream which can be obtained by intersection of Fanno and Rayleigh lines proceeding through diffuser [4]. At outlet of diffuser mixed stream velocity is negligible. In 1942, the constant pressure mixing theory of ejector was developed by Keenan and Neuman .They assumed constant pressure mixing ejector and many researchers used their study for further research work [5]. Sun and Eames described a simulation model for ejector refrigeration applications using working fluid as refrigerant R123 in place of R11. Their results showed that R123 is good alternative for R11 in air conditioning purposes. They also studied the effect of variable geometry on the performance of system at variable operating conditions for optimum results [6]. Nehdi et al. [7] performed experiments on supersonic ejector and found result for optimum designing of ejector with Refrigerant R11. Diswas and wongwises experimentally investigated the performance of ejector expansion refrigeration cycle without expansion valve of evaporator and their results showed improvement in coefficient of performance relative to conventional cycle [8]. Alexis predicted the main cross-section of ejector for refrigeration applications [9]. Salvaraju and Mani developed computer program to investigate the effect of specific heat of working fluid and friction on constant area mixing chamber [10]. II. EJECTOR PERFORMANCE AND MATHEMATICAL MODELING An ejector is a device which is used to entrain low pressure fluid by high pressure fluid without any mechanical power input. In fig.1 demonstrate the working of ejector system in which high pressure superheated vapour raised in generator (6). Now these vapours passes through ejector (2) in
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