Review of advanced absorption cycles: performance improvement and temperature lift enhancement

The objective of this study is to propose and evaluate advanced absorption cycles for the coefficient of performance (COP) improvement and temperature lift enhancement applications. The characteristics of each cycle are assessed from the viewpoints of the ideal cycle COP and its applications. The advanced cycles for the COP improvement are categorized according to their heat recovery method: condensation heat recovery, absorption heat recovery, and condensation/absorption heat recovery. In H2O–LiBr systems, the number of effects and the number of stages can be improved by adding a third or a fourth component to the solution pairs. The performance of NH3–H2O systems can be improved by internal heat recovery due to their thermal characteristics such as temperature gliding. NH3–H2O cycles can be combined with adsorption cycles and power generation cycles for waste heat utilization, performance improvement, panel heating and low temperature applications. The H2O–LiBr cycle is better from the high COP viewpoints for the evaporation temperature over 0°C while the NH3–H2O cycle is better from the viewpoint of low temperature applications. This study suggests that the cycle performance would be significantly improved by combining the advanced H2O–LiBr and NH3–H2O cycles.