SINGLE STAGE TRIPLE PRESSURE LEVEL ABSORPTION CYCLE BASED ON REFRIGERANTS R22, R32, R125, R134a AND R152a WITH DMEU

摘要

Current developments in absorption technology include the research for new working pairs and new advanced cycles that would facilitate increased efficiency of absorption units and extend applicability to different temperature ranges. Four HFC refrigerants diflouromethane (R32), pentafluoroethane (R125), 1,1,2-tetrafluoroethane (R134a) and 1,1-diflouroethane (R152a) which are alternatives to HCFC, such as colorodiflouromethane (R22), in combination with absorbent dimethylenurea (DMEU) were evaluated for possible utilization in absorption chillers powered by low temperature heat sources. A computerized simulation program was used to compare the different refrigerant-absorbent pairs. The program was based on an advanced single-stage triple pressure level (TPL) cycle containing a jet ejector. The absorption cycle was represented in terms of heat and mass balances for each component and the calculations were based on the thermophysical properties of the refrigerant-absorbent pairs measured and evaluated in our laboratory. The aim of the cycle analysis was to evaluate the highest coefficient of performance (COP) and the lowest circulation ratio (f), which can be obtained for different generator temperatures for a given evaporating and cooling water temperatures. At the maximum COP of each working pair, the effects of changes in the evaporator and the cooling water temperatures on the COP and the circulation ratio,f, were also examined. The performances of the working fluids based on HFC refrigerants-DMEU pairs were compared with the performance of R22-DMEU. It was obtained that the generator temperature of R125-DMEU at maximum COP is lower than those obtained with the other alternative working fluids.