Cooling of water flowing through a night sky radiator

Experimental and theoretical studies of nocturnal cooling of water flowing through a night sky radiator unit were carried out. The system used for this study is two parallel plates night sky radiator with the top one (radiator) being a painted black aluminum plate. The radiator plate was covered by a polyethylene windscreen cover. The experimental study was conducted for a gravity flow open loop system. The parameters studied include the effect of average water mass flow rate, uncovered from the ambient versus covered supply warm water tank, and windscreen cover thickness on the performance. A new definition of the performance was expressed by an overall efficiency. A comparison between nocturnal cooling of stagnant and flowing water was also done. In the theoretical study a thorough radiation model was developed which calculates the radiation heat losses from both the cover and the radiator plate considering multiple reflections and absorptions between cover and plate. Energy balance was then applied on the cover, the radiator plate and the water. The cover and insulation were considered one lump each, while each of the radiator plate and the water were divided into discrete number of lumps. Energy storage in the radiator frame and insulation, and water elements was considered. Experimental results were used for verification of the theoretical model.