SINGLE-AND DOUBLE-STAGE ABSORPTION CYCLES BASED ON FLUOROCARBON REFRIGERANTS AND ORGANIC ABSORBENTS

A comparison between different fluorocarbon refrigerants and organic a bsorbents as working fluids in single- and double-stage absorption hea t pumps was undertaken. The refrigerants included R22 (monochlorodiflu oromethane), R134a (1,1,1,2-tetrafluoroethane), R124 (2-chloro-1,1,1,2 ,-tetrafluoroethane) and R32 (difluoromethane), and various organic co mpounds such as DMAC (N,N'-dimethylacetamide), DMEU (dimethylethyleneu rea), DMETEG (dimethylether tetraethyleneglycol), NMP (N-methyl-2-pyrr olidone), and MCL (N-methyl epsilon-caprolactam) constituted the absor bents. The single- and double-stage cycles were calculated for the fol lowing working conditions: cooling capacity of 100 kW, generator tempe rature of 100 degrees C, evaporator temperature of -10 degrees C, wate r-cooled components outlet temperature of 35 degrees C, and the air-co oled components outlet temperature of 50 degrees C. The performance ch aracteristics of the working fluids in both cycles in terms of the coe fficient of performance (COP) and the circulation ratio (f), the heat transfer in the main components, the refrigerant and solution mass flo w-rates, and the water flow-rates were calculated and compared. Under these working conditions, the performance of the working fluids based on R22 are superior to those based on R124 in both cycles. The working fluids based on R134a cannot be used in a single-stage absorption cyc le while in a double-stage cycle the performances were the worst; solu tions based on R32 cannot be used in either cycles. (C) 1998 Elsevier Science Ltd. All rights reserved.