Analysis of the Energy-Saving Effect of a Novel Central Air-Conditioning System with an Internal Heat Exchanger in Summer

In this paper, a novel central air-conditioning system with an internal heat exchanger is proposed and analyzed for its energy-saving effect. Two frequently used systems are chosen as the reference systems, i.e., a conventional system with a sensible heat exchanger (Reference System I) and a conventional system with a total heat exchanger (Reference System II). Analysis models are built to simulate the performance of the system. The energy-saving effects of the proposed system and the two reference systems under different conditions are theoretically calculated using a case-studied shopping mall in Nanjing, China. The results show that the influence of indoor relative humidity (RH) on the energy-saving effect is much greater than that of the indoor design temperature. Indoor design parameters have a greater impact on energy saving than outdoor design parameters. Under the studied conditions, the maximum energy-saving rates of the proposed system, Reference System I, and Reference System II, are 52.7%, 2.3%, and 12.1%, respectively. With the decrease in fresh-air ratio from 70% to 20%, the difference in energy-saving rates between the proposed system and Reference System II (Reference System I) can increase from 5% to 23% (15% to 30%). Therefore, the proposed system has obvious energy-saving potential and advantage, especially under the condition of a lower fresh-air ratio.