The design and mathematical modelling of thermal radiator panel to be used primarily to measure night sky radiation wet coated surface is presented in this paper. The panel consists of an upper dry surface coated aluminium sheet laminated to an ethylene vinyl acetate foam backing block as an insulation. Water is sprayed onto the surface of the panel so that an evaporative cooling effect is gained in addition to the radiation effect; the surface of a panel then is wetted in order to study and measure the night sky radiation from the panel wet surface. In this case, the measuring water is circulated over the upper face of this panel during night time. Initial TRNSYS simulations for the performance of the system are presented and it is planned to use the panel as calibrated instruments for discriminating between the cooling effects of night sky radiation and evaporation. 1. Introduction The demand for energy efficient air conditioning systems to minimize the energy consumption worldwide has been an important issue for researchers since the invention of active air conditioning system. In parallel with the researches conducted to create new conventional air conditioning technologies, researches to find noncompressor systems took a place. Noncompressor cooling systems have been introduced as low electricity consumption alternatives to mechanical vapour compression units, providing a solution that reduces the energy consumption and environmental issues in buildings. Absorption and adsorption chillers, direct and indirect evaporative air coolers, and water passive cooling systems which utilize the night sky radiation effect are among the range of noncompressor systems available. Radiative cooling is a passive cooling process based on the phenomenon of heat transfer between earth-based objects and the sky by the means of long-wave radiation, usually when the effective sky temperature is less than the ground temperature. The transparency of earth’s atmosphere in the infrared range of 8–13？μm (atmospheric window) allows a fraction of the thermal radiation to be absorbed by space, especially during the night and early morning where solar short wave radiation is absent. The phenomenon can be applied to cool surfaces and/or fluids, which in turn can be used in air conditioning applications. Cooling with night sky radiation phenomena could be considered as featured technology with capability to be a passive alternative to the conventional air conditioning system. Many researchers have explored the different applications and systems proposed to cool fluids by means of
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