Process design, performance comparison and operating test of the multi-stage vertical absorption heat exchanger realizing independent heating in three zones

Abstract

Absorption heat exchangers applied in district heating systems can significantly reduce the outlet water temperature of the primary network, thereby expanding the heating scale and promoting low-temperature waste heat recovery. However, nearly 50% of the existing heating systems in high-rise buildings are divided into three independent zones. At present, there is a lack of research for absorption heat exchangers in this scenario. The main task of this paper is to address this issue to expand the application range of absorption heat exchangers. Firstly, two different processes are designed in this paper. The first process is to add a plate heat exchanger in the existing two-stage process, while the second process is a novel three-stage vertical process, consisting of three absorption heat pumps with different pressures and three sets of plate heat exchangers. Then, the operating performance, self-adjustment ability and the system cost of different processes are compared based on the simulation method. Although the price of Process 2 is 26.4% higher than that of Process 1, the efficiency of Process 2 is 20.3%-27.7% higher, and the self-regulation ability is significantly better. Thus, Process 2 has better overall performance. Moreover, the system development and operating test of Process 2 are conducted. Throughout the whole heating season, the overall efficiency of the system is 1.17–1.23. Without manual intervention, the relative standard deviations of the inlet water temperature of the secondary network and the actual heat supply rate ratio are less than 5% and 16% respectively, which proves that the system has great self-adjustment ability. The conclusions in this paper can guide the design and application of the absorption heat exchanger in three-zone independent heating scenarios.