Analysis of cooling performance and energy consumption of nocturnal radiation and natural ventilation combined mechanical refrigeration system for outdoor prefabricated substation

Abstract

To make full use of renewable energy and reduce cooling energy consumption, a new structure nocturnal radiation board was designed, modeled and experimentally studied, and a combined refrigeration system of air/water-cooled chiller, nocturnal radiation board and natural ventilation unit was proposed and simulated with the building model of a prefabricated substation in Zhenjiang city in China. The research results of the nocturnal radiation board show that the average cooling heat fluxes are about 40.24, 70.40 and 37.84 W/m2 on a typical sunny summer day, a cool autumn day and a rainy summer day, respectively. The average cooling heat flux ratio of experimental results to calculating results is about 0.75, which can be taken as the model modification coefficient to predict the cooling heat flux of the nocturnal radiation board. The hourly dynamic simulation results of the combined refrigeration system show that the energy saving rates of 37.65%, 44.80% and 62.24% can be achieved on a typical summer day, a cool autumn week and the whole year when compared with the conventional air-cooled chiller system. The annual coefficient of performance of the combined refrigeration system is about 15.31, which is more than 2.7 times that of the conventional air-cooled chiller system. The proposed nocturnal radiation board and combined refrigeration system can make full use of nocturnal radiation energy and air energy for space cooling and significantly reduce the cooling energy consumption.