Investigations on the Cycle Performance of a Diffusion Absorption Heat Transformer Using HCOOK as an Alternative to LiBr

A diffusion absorption heat transformer (AHT) is very potential to improve energy utilization efficiency and reduce carbon emission, because it can be totally driven by waste heat without electricity consumption. On the base of a simulation model, the cycle performance of a diffusion absorption heat transformer using HCOOK-H₂O-R134a-TEGDME and LiBr-H₂O-R134a-TEGDME is compared under specified temperatures of Generator A, Generator B, evaporator, condenser, low-temperature (LT) absorber, and high-temperature (HT) absorber. The influences of six temperatures on cycle performance are assessed and coefficient of performance (COP) is found more sensitive to the temperatures of Generator B and high-temperature absorber. High COP corresponds to small diffusion gas supply ratio and small proportion of the heat input to Generator A in the total thermal power input. The employment of HCOOK instead of LiBr is beneficial to increasing COP in optimized conditions. In the design temperature conditions, COP can be increased from 0.170 to 0.178 in the system using HCOOK instead of LiBr. Meanwhile, diffusion gas supply ratio, proportion of the heat input to Generator A, and pumping ratio (PR) of Lifting Tube B can be decreased to 0.368, 0.022, and 0.098, respectively. The diffusion absorption heat transformer will provide a new way to lift the temperature of low-grade heat for more availability without electricity input and improve the energy utilization efficiency.