Thermodynamics Analysis And Prototype Design Of The Absorption Heat Transformer At High Temperature

The Absorption Heat Transformer (AHT) is a kind of device which can use the absorption cycle of the working fluid to transfer the energy from low-temperature to the higher one. This system can not only recover and utilize waste heat, but also decrease the thermal pollution discharged to the environment, and attracts more and more attention in the international community of energy utilization.Most of the current investigations focus on the low and moderate temperatures, but for high temperature, the publically available report is very limited. So in this paper, based on the mass conservation, the heat conservation as well as the momentum conservation, and also combine with the thermodynamic properties of lithium bromide-water at high temperature, the effects of evaporation temperature, condensation temperature, the concentration of the aqueous lithium bromide solution and the concentration difference on the gross temperature lift, the coefficient of performance and the thermal effectiveness are analyzed systematically from the viewpoint of thermodynamics.To meet the designed target of the AHT experiment, we assign the coefficient of performance as the objective function, and optimize the system cycle in a specified range of operating parameters. Some optimized operating parameters are obtained, including the evaporation temperature of 165℃, the condensation temperature of 124.9℃, the concentration of the strong aqueous lithium bromide solution 52%, and the concentration of the weak aqueous lithium bromide solution 48%. At these conditions, the gross temperature lift, the coefficient of performance and the thermal effectiveness can be achieved as 37.1℃, 0.43 and 0.72, respectively. Furthermore, a prototype AHT is designed for experiments, with the output available energy of 5.2 kW at high temperature above 200℃.In addition, an ejector is introduced into the cycle to improve the overall performance of AHT. Thermodynamics analysis of the Ejection-Absorption Heat Transformer (E-AHT) shows that its gross temperature lift is higher than that without ejector, and with the compression ratio is 1.2, the gross temperature lift can increase about 22.7%, the thermal effectiveness increases 3% and the coefficient of performance decreases 2.5%.