Publication date: July 2015
Source:Building and Environment, Volume 89
Author(s): Shang Wang , Yuguo Li
The globe thermometer has been commonly used as a meteorological instrument for measuring the mean radiant temperature for at least 80 years. Originally it consisted of a hollow copper sphere. In recent years, the acrylic globe thermometer has also become widely used for outdoor measurements because of its fast response and being more economical to produce. However it has been found that the mean radiant temperature measured by an acrylic globe thermometer is mostly inconsistent with that of the more accurate three-dimensional integral method. To investigate why such a discrepancy occurs, static indoor experiments and dynamic outdoor experiments were conducted to compare and explore the thermal response of both a copper and an acrylic globe thermometer. The measurements were also compared with theoretical predictions. In addition, the spatial distributions of temperature on the exterior surface and along the interior axis of the globe were measured. The effect of surface optical properties was also discussed. The primary reasons for the temperature differences between copper and acrylic globe thermometer are analysed. Based on above analysis, we conclude that the acrylic globe thermometer is not suitable for the measurement of outdoor diurnal mean radiant temperature. The conclusions are then generalized to metallic and non-metallic globes.
Source:Building and Environment, Volume 89
Author(s): Shang Wang , Yuguo Li