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Title: Ejector Driven Refrigeration Systems
Keywords: Roto-dynamic Ejector, Green refrigeration, Ejector efficiency, Ejector systems, Ejector modelling, self driving ejectors
Issue Date: 18-Jan-2012
Source: SAMUEL DEVRAJ ARULMANI (2012-01-18). Ejector Driven Refrigeration Systems. ScholarBank@NUS Repository.
Abstract: Ejector driven systems, wherein an ejector is used as a thermal compressor are a viable alternative to traditional vapour compression refrigeration systems since they are simple to construct, operate and maintain. However their popularity has been limited by low COP and small operating windows. This project is aimed at trying to improve the performance of these systems so as to make them more attractive. The associated work carried out is reported as follows; 1. Traditional Ejector Model Development: A 1D model was developed in MATLAB to predict the performance of the ejector using conservation laws. The model helps to understand the working of an ejector and to predict the performance for different geometries and operating conditions. 2. Alternate Refrigerant Prediction for Existing Ejector Systems: Most of the Ejector systems currently in operation use refrigerants which have high Global Warming or Ozone Depletion Potential. The validated 1D model is used to propose suitable alternate environment-friendly refrigerants for existing ejector systems currently using older refrigerants. Base refrigerants considered are R11, R123 and R141b. Replacement refrigerants analysed are R134a, R245fa, R245ca, Water (H2O) and Ammonia (NH3). In general, ammonia and R134a develop a much higher entrainment than the base refrigerants. However they also have high operating pressures. R245fa and R245ca have operating pressure ranges very close to those of the base refrigerants. But their entrainments are often slightly lesser than those of the base refrigerants. 3. The Roto Ejector Concept and Model Development: The Traditional Ejector model has then been modified to simulate the performance of a ¿Roto-dynamic Ejector¿. The developed model is used to compute the expected performance for different refrigerants. 4. Comparison of Traditional and Roto-Ejector performances: The Traditional and Roto Ejector model performances are compared and improvements are gauged. It is observed that incorporating a Roto-ejector can improve the COP of a system up to 30% over that of the traditional ejector. The Entrainment ratio is also increased by 12 ¿ 29%.Based on the results, conditions for optimal operation are proposed.
Appears in Collections:Master's Theses (Open)

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