Single stage absorption system based on refrigerants R125 and R134A with DMETEG

Abstract

Current developments in absorption technology include the research for new working pairs and new advance cycles that would facilitate increased efficiency of absorption units and extend applicability to different temperature ranges. Two refrigerants tetrafluoroethane (R134a) and pentafluoroethane (R125) that are alternatives to chlorofluorocarbons, in combination with absorbent dimethylether teraethylene glycol (DMETEG) were evaluated for possible utilization in absorption machines 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 advance single-stage cycle containing a jet ejector. The absorption cycle was represented in terms of heat and mass balance 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 under a constant evaporating and cooling water temperatures. The effects of changes in the evaporator and the cooling water temperatures on the COP and the circulation ratio, f, were also examined at the generator temperature at maximum COP.