Thermodynamic Performance Assessment of Air Conditioner Combining Evaporative and Passive Cooling

Abstract

The global increase in refrigeration and air conditioning applications poses a severe problem as regards the environmental degradation caused by greenhouse gas emissions. This study introduces a novel approach wherein both evaporative cooling and passive cooling are integrated to unveil notable enhancements in energy and exergy compared to conventional air conditioning systems. Therefore, this work aims to enhance the thermal performance of a 1.5-ton split air conditioner (SAC) employing outdoor (condenser) evaporative and indoor passive cooling (EPC). The heat removal capacity of a condenser and SAC performance are greatly affected by the air temperature at the condenser inlet. Evaporative cooling serves to lower outdoor air temperature, while passive cooling minimizes the indoor cooling load. Design parameters encompass outdoor temperature (Ta = 30–44 °C), relative humidity (RH = 20–80%), and temperature reduction due to passive cooling (ΔTR = 0.5–5 °C). A model is developed to calculate the temperature reductions of outdoor air through evaporative cooling in diverse climatic conditions, while the range of passive cooling degrees is obtained from previous experiments. Results indicate a substantial enhancement in the thermodynamic performance of the proposed system. The maximum coefficient of performance (COP) improvement of 68.66% is achieved at 44 °C outside temperature and 20% relative humidity. Annual energy savings, under extreme operating conditions, range from 358.4 kWh to 2116.8 kWh. The EPC SAC is identified as more sustainable than the conventional split air conditioner (CSAC). Moreover, the projected system is anticipated to recoup its costs within a relatively short period of 1.42 years.