Study on performance of seawater-based evaporative cooling integrated with desiccant wheel air-conditioning system for marine vessels

In this study, a hybrid air-conditioning system consists of a desiccant wheel (DW) driven by the waste heat of ships and a dew point indirect evaporative cooler (IEC) utilizing seawater as a cooling medium is proposed as an energy-efficient alternative to the conventional ship air-conditioning system for the dehumidification and cooling of the cabins of marine vessels. A numerical model including a DW and an IEC was developed. Different from traditional IEC which relies on pure water evaporation, research highlights are placed on the characteristics of seawater evaporation in the model establishment by taking account of the thermophysical properties of seawater. By using the energy consumption, dehumidification capacity and cooling capacity as indicators, the effects of six operating parameters on the system performance are investigated and optimized. Case study is also conducted to reveal the air handling processes and energy performance under typical operating conditions. The results show that the outlet air temperature of seawater based IEC is slightly higher than that of pure water-based IEC with a difference of only 0.86 % to 1.35 %. The hybrid air-conditioning system exhibits excellent dehumidification and cooling capacity at higher inlet air temperature, humidity and regeneration temperature, with a coefficient of performance (COP) up to 12.6. Compared with the traditional vapor compression refrigeration system, the energy saving rate of hybrid air-conditioning system can reach 61.62 % by consuming only 10.5 % of the ship's residual heat. The hybrid air-conditioning system provides a low-carbon and sustainable air-conditioning solution for the marine vessels.