A novel method and operation strategy for the improved performance of an absorption heat transformer

Recently, waste heat recovery in industry applications of absorption heat transformers has developed rapidly. Due to the instability of the heat source and constantly changing heat load, it is difficult to adjust and control an absorption heat transformer to meet the needs of heat supply and heat consumption. Thus, the dynamic performance caused by thermal inertia and solution concentration inertia becomes increasingly important. A dynamic model of a vertical falling-film absorption heat transformer using LiBr/H2O as the working pair is established in this paper and validated by experimental data. The simulation results show that there is a contradiction at different stages of equipment operation. Less solution reserved in the system is more advantageous during start-up and load changing, but reserving less solution is opposite under internal and external fluctuations. Thus, a system improvement method and operational strategy are proposed to resolve this contradiction. The improved system has a faster temperature stabilization speed and higher total Coefficient of performance (COP) under start-up, load changing, and operating condition fluctuations. The stabilization time for start-up and load changing processes can be reduced by 43.8%, and a 20 kW absorption heat transformer can save about 212.2 kJ for each load changing operation.