A quantitative metric for the indoor environment radiative field asymmetry developed through numerical simulation of the radiative field structure

Abstract

Radiative exchange in the indoor environment contributes significantly to the thermal comfort sensation reported by human subjects. The radiative exchange can have a strong directional character, depending on the temperature and size of various surfaces such as glazed areas, radiant panels, etc. Radiative asymmetry is known to cause varying degrees of thermal discomfort. The paper proposes a numerical simulation approach to characterize the asymmetry of the radiative field in a rectangular section enclosure. An enclosure with fixed dimensions was considered and the number and position of glazed areas were varied. Three shapes of virtual sensor were considered: rectangular prism, cylinder and sphere. The total heat flux exchanged by the sensor with the surfaces of the enclosure was determined. By varying the position of the sensor in the enclosure, a set of heat flux values associated to each sensor position was generated (a radiative field). A measure of radiative field asymmetry (radiative asymmetry coefficient) is proposed in this paper as the ratio between maximum and minimum values of the heat flux density. It was found that the most comprehensive characterization of the radiative field asymmetry can be obtained by employing a spherical sensor. The spherical sensor allows a two-fold definition of the radiative asymmetry coefficient with one value in the horizontal plane and another value in a vertical plane. The novel metric proposed here provides a more complete characterization of the radiative field than the conventional Radiant Temperature Asymmetry.