Allowable surface temperature of ceiling heating based on radiant temperature asymmetry

Radiant temperature asymmetry as one of the criteria for local thermal discomfort has an influence on the practical design of the heating system, as people are most sensitive to the radiant heating of the top of the head. The paper presents the determination of the allowable surface temperature of the heated ceiling based on the theoretical calculation using the angle factors and taking into account the allowable the radiant temperature asymmetry according to the standard values of 5 and 7 K. In practice, the radiation temperature asymmetry is determined by measuring two radiant temperatures. In this paper, the measurement of radiant temperature asymmetry is measured in an experimental room with a heated ceiling and the results are compared with the theoretical calculation procedure. The paper points out the differences between the measured and calculated values of the radiant temperature asymmetry. Based on the analyses, the allowable ceiling temperatures for radiant heating have been determined for different room geometries so that the radiant temperature asymmetry for thermal comfort categories A, B is actually observed. A new correlation has been established to determine the allowable surface temperature of the radiant ceiling as a function of the angle factor between the small plane element and the ceiling. For practical use, the correlation has been adjusted for typical geometric cases without the need for calculation of angle factors. Maximum ceiling surface temperatures are graphically displayed without causing thermal discomfort. Conversely, in large rooms with a heated ceiling, the ceiling surface temperature is severely limited, precisely because of the potential for thermal discomfort due to radiant temperature asymmetry.