Mean radiant temperature calculated from globe thermometer data: critical data analysis of a field study

Abstract

The mean radiant temperature (Tmrt) is one of the main variables used in studies on the perception and thermal performance in/of buildings. Usually, it is obtained indirectly, with procedure based on data from globe thermometers. In certain situations, this procedure may return inaccurate results. The aim of this study was to verify the reliability of Tmrt obtained considering data of globe thermometer using ping-pong ball. Tmrt obtained considering this equipment were compared with those obtained when using form factor and surface temperatures. Different environmental contexts of a test building were analyzed: a) Without cooling and without forced ventilation; b) With passive cooling and without forced ventilation; c) With passive cooling and forced ventilation; d) With mechanical cooling and forced ventilation. In all the analyzed contexts it became evident that the globe temperature is more related to the air temperature than to the average radiant temperature. In cases ‘a’ and ‘b’, the results indicated small differences between the results obtained by the two procedures. In case ‘c’, the differences were significant, and in case ‘d’, were even greater, generating uncertainty about the use of the equipment.