Performance comparison of absorption heating cycles using various low-GWP and natural refrigerants

Absorption heating is potential in building energy saving and emission reduction. To overcome the problems of conventional absorption working fluids and to explore more alternatives, absorption heating cycles using various low-GWP and natural refrigerants are compared. Property models of different working fluids have been chosen and developed with good accuracies. The models of single-effect and compression-assisted cycles are built with verified accuracies. Simulations revealed that H2O-LiBr has the best heating performance, but is highly restricted by crystallization and freezing. NH3-H2O has good performance and wide applicable range, but has the concern of toxicity. Among the HFC-based fluids, R161-DMF has the highest COP of 1.448-1.496 when generation temperature is above 145 °C, 1.414-1.674 when evaporation temperature is above 8 °C, 1.745-1.409 when condensation temperature is below 52 °C, otherwise R152a-DMF performs the best. R134a-DMF has quite similar performance to R152a-DMF, while R32-DMF has the lowest COP in the whole temperature ranges. In the compression-assisted cycle, the minimum generation temperature can be reduced from 92-130 °C to 65-80 °C, and the minimum evaporation temperature can be reduced from −8 to 6 °C to −20 to −12 °C under a compression ratio of 2.0. Primary energy efficiency of R161-DMF can be increased to 1.146-1.327 under generation temperature of 65-130 °C, and to 1.117-1.330 under evaporation temperature of −10 to 10 °C.