Improving heat supply of ammonia-water absorption heat transformer by enlarging heat source utilization temperature span

Abstract

Compared with the LiBr–H2O absorption heat transformers, the NH3–H2O ones show greater application potential without the risk of crystallization and corrosion at high operating temperatures, while with the main drawback of lower COP. However, the heating capacity of systems at given heat source conditions attracts more attention for users than COP. Therefore, this work aims to increase the heating capacity of the NH3–H2O system by enlarging the temperature utilization span of the heat source. To achieve this, a temperature-changing generation process is introduced and generator configurations are modified. The comparison results with the literature indicate that the heating capacity of the proposed NH3–H2O system at given heat source conditions is equal to and even higher than the LiBr–H2O systems. In addition, it is found that the temperature matching with the heat source influences the system exergy efficiency. The maximum system exergy efficiency of 49.7% is realized when the optimum temperature matching is achieved. It is hoped that this work has eliminated influences of low COP drawbacks on NH3–H2O absorption heat transformers and promotes its practical application of low-grade heat recovery and low-carbon heating.