Thermal efficiency analysis of a night radiator prototype

Abstract

This study focuses on nocturnal radiative cooling as a passive way of cooling buildings. Due to the lack of studies on the radiator’s features that determines its efficiency, the thermal performance of a prototype radiator was characterized according to three methods: (a) the analytical method to quantify the cooling potential of a surface exposed to the local atmospheric conditions; (b) a field experiment with a pilot system; and (c) a CFD numerical method. All methods used the same environmental data collected in the field experiment as input. Experimental results showed similar behavior to the theoretical cooling achieved by the analytical method. Likewise, the simulations’ results allowed the prediction of the thermal behavior of the prototype radiators. Both CFD simulations and thermal images enabled the identification of a steep decline in temperature in the initial stretch of the prototype radiator and its stagnation in the remaining water path. Thus, a parallel arrangement was simulated for the water channels and improved performance up to 9.6%. Besides showing that the CFD simulations are a viable alternative to determine the arrangement of the radiators, this study concluded that parallel oriented flow could increase the cooling rate and thermal efficiency.

Keywords: Nocturnal radiative cooling. Prototype radiator. Passive cooling. Thermal simulation in CFD.