Study on the energy performance of a multi-mode split evaporative-cooling hybrid air-conditioning system

Reducing energy consumption in buildings is a crucial component in the pursuit of carbon neutrality and sustainable social development. The air-conditioning systems account for a significant portion of a building's energy consumption and therefore require special attention to their energy efficiency. These air-conditioning systems that incorporate indirect evaporative cooling (IEC) technology are a viable energy-saving strategy. However, these hybrid systems are mainly designed for hot-dry climates, and limited research has focused on the coupling advantages of condenser pre-cooling and reheating energy recovery via IEC through different operating modes. In this paper, a novel multi-mode split evaporative-cooling hybrid air-conditioning system (MVC-IEC) is proposed, which utilizes the IEC cycle to achieve condenser pre-cooling and supply air reheating. Simultaneously, it features five operating modes to adapt to the changing ambient climatic conditions. Subsequently, the energy performance of the MVC-IEC system was primarily investigated under different operating conditions. The MVCIEC demonstrates a more pronounced energy-saving advantage under high temperature, medium-low humidity and low reheat load conditions. In addition, the MVC-IEC has acceptable application potential in both hot-humid and hot-dry cities (Changsha, Nanjing, Zhengzhou and Xi'an). The seasonal COP for the MVC-IEC is reached by 3.9 - 4.6. And compared with MVC-HRC, the MVC-IEC achieves an energy-saving rate of 10.8 - 16.3 % and reduces carbon emissions by 0.42-0.80 kg/year.