DEVELOPMENT OF A VAPOUR COMPRESSION REFRIGERATION SYSTEM BASED ON BALANCED POINTS BETWEEN OPERATIONAL UNITS

Abstract

Vapour Compression Refrigerator (VCR), consists of four major components- evaporator, condenser, compressor and expansion device, which are connected in a cycle. VCR is commonly used in a wide range of commercial and industrial refrigeration applications and represents a substantial fraction of the installed refrigeration systems. As a result special attention has been focused on this system by many researchers. The goals of the researchers were to simulate the actual working of a vapour compression system with Carnot model as the benchmark. The task of getting the performance of Carnot model has proved difficult. Hence most researchers end-up in modeling performance of heat exchangers or a single component of the system. Though there are models for predicting the approximate performance of VCR, none of such models discussed, the "balanced point" between the four major components. This study was carried out to investigate the effects of balanced point on the system performance. In order to get the balanced point, the performance characteristics of each of the components were modelled in such a way that each of them depends on temperature only. These equations were used to develop a computer programme for refrigeration cycle. The model was then used to generate performance data, which compare very well with theoretical values. In order to validate the model, the generated data was used to design and construct a VCR that was tested and evaluated. Two experimental rigs were constructed for the tests. Rig "a" was that constructed using generated data from the design model, whilst Rig "b" was constructed from bought out components. The investigations were carried out under the same conditions. Effects of system performance based on operational parameters such as: compressor speed, refrigerant charge, condenser and evaporator temperatures and others, have been experimentally evaluated and the results compared. Present analysis and experimental investigations have shown that the model results are comparable to the experimental ones. The results obtained from rig a agreed well with those of the model, although there were some deviations. The deviations of the model results from those obtained in experiments are within the ranges of 16 % to 19 % for rig "a" and 28 % to 34 % for rig "b" respectively.