Performance investigation of a high-temperature absorption-compression heat transformer with liquid refrigerant injection

The high-temperature heat pump technology is a promising approach to utilizing low-temperature waste heat while meeting industrial demands for high-temperature heat. However, existing high-temperature heat pump systems face challenges including insufficient temperature lift, system complexity, and rapid performance degradation at high output temperature. This paper proposes a novel, structurally simple high-temperature absorption-compression heat transformer, aiming to recover heat below 100 degrees C and achieve a large temperature lift above 70 degrees C. The system is analyzed from the aspects of energy, exergy, key parameters that impact its performance, and techno-economic comparison. Results show that injecting liquid refrigerant into the compressor chamber mitigates high superheat effects on the compressor, allowing for higher absorption pressure. The system achieves an output temperature of around 170 degrees C, with the compressor outlet temperature below 120 degrees C. Moreover, some liquid refrigerant evaporates by absorbing compressor superheat. This reduces power consumption of the compressor, heat input of the evaporator, and overall system exergy loss. Thus, the proposed system demonstrates improvements of 6.5 % and 7.5 % in coefficient of performance and exergy coefficient of performance, respectively. Besides, it is feasible to achieve absorption temperatures exceeding 170 degrees C by increasing the solution concentration or the pressure ratio, with the former being the more cost-effective approach. Furthermore, the specific costs of the proposed system are more than 20 % lower than those of other types of high-temperature heat pumps, demonstrating its superior economic feasibility.