Anticipating an efficient relative humidity in a room under direct solar radiation and equipped by radiant cooling panel system

Abstract

In the present study the performance of radiant cooling ceiling system in a room under direct solar radiation is investigated by combination of numerical and analytical solutions. Assessments are implemented in four distinct climates in Iran which include Tabriz (dry and cold), Tehran (mild and dry), Rasht (mild and humid) and Yazd (dry and hot) in the hottest hour of the hottest day of the year 2017. Efficient surface temperatures of the ceiling are determined to supply thermal comfort conditions. Turbulent flow, radiation, solar radiation is modeled by Low-Reynolds k-ε model, discrete ordinate model and ray-tracing model, respectively, by FLUENT 6.3 software. To avoid condensation, critical RH method is defined to determine suitable RH accurately. Thermal comfort is investigated by PMV index. The energy saving effect of coated glass is also illustrated. Results demonstrate that by using coated glass, energy usage can be reduced 49–58%. Furthermore, changing room's orientation from west to south can boost the energy saving. Accordingly, the higher ceiling temperature which provides thermal comfort for occupants means the lower condensation probability; hence, radiant cooling ceiling systems could be utilized even in the mild and humid climate without dehumidifying necessity.