Comparative Study of Experimental and Theoretical Evaluation of Nocturnal Cooling System for Room Cooling for Clear...

Nocturnal radiation is one of the effective passive cooling technologies by infrared radiation exchange between earthly surfaces and the sky. Heating ventilation and air conditioning (HVAC) systems are highly energy-demanding and there is a need to develop alternative low-energy means to achieve comfort. Radiative cooling reduces the electricity requirements, which normally is generated through fossil fuels, in order to run active cooling systems. During the day, this is offset by solar radiation gains on the roof; however, at night, this heat loss has the ability to cool air, as roofs can experience a temperature drop of 2-12 °C below ambient. The experimental investigation of the aluminum material and their surface colors on nocturnal cooling is presented for clear and cloudy sky conditions. The material of aluminum and black color coating are considered. Results obtained reveal that the plates' performances greatly depend on the presence of clouds in the night. The best results are obtained in a clear sky summer climate condition than in the cloudy sky condition. The net cooling rate of night sky radiation system for without and with coating on aluminum of mass flow rate 0.05 kg s^-1 is near about 72.30-80.99 W m^-2 for clear sky and 48.75-53.25 W m^-2 for cloudy sky condition.