Designing, Modelling and Experimental Investigation of Direct Evaporative Cooling System Coupled With Commercial Desiccant Dehumidifier

Abstract

With the increasing demand of clean and energy-efficient air conditioning systems, evaporative air cooling technique is gaining significant attention owing to less energy consumption and environmentally safe technology in comparison with conventional refrigerant-based air conditioners. In this study, commercial desiccant dehumidifier is coupled with experimentally developed direct evaporative cooling (DEC) system to first dehumidify the air and then pass it through DEC to achieve human thermal comfort level defined by ASHRAE standards. Under the climatic conditions of Islamabad, Pakistan, multiple experiments were carried out at different temperatures, flowrate, and relative humidity of air during November, when air temperature and relative humidity were in the range of 25–30 °C and 40–60%, respectively. To analyze the system performance under summer ambient conditions, indoor temperature was increased by 8–10 °C and relative humidity by 15–25% in laboratory. Experimental analysis showed that the system can provide human comfort level for a range of temperature 29–39.7 °C and relative humidity of 65–80% at flowrate of 180 m3/h. To achieve thermal comfort at higher humidity level, DEC is coupled with commercial desiccant dehumidifier. However, due to desiccant regeneration by an electric heater in the dehumidifier, the overall power consumption of the whole system increases up to 1.95 kW. Two well-known indices coefficient of performance (CoP) and energy efficiency ratio (EER) are used to analyze the system performance. Experimental analysis revealed that CoP decreases with the increasing specific humidity of air, decreasing ambient temperature, and flowrate.