Looking for simple correction functions between the mean radiant temperature from the 'standard black globe' and the 'six-directional' techniques in Taiwan

摘要

Mean radiant temperature (T-mrt) values were calculated and compared to each other in Taiwan based on the six-directional and globe techniques. In the case of the six-directional technique (measurements with pyranometers and pyrgeometers), two different T-mrt values were calculated: one representing the radiation load on a standing man [T-mrt(st)] and the other which refers to a spherical reference shape [T-mrt(sp)]. Moreover, T-mrt(T-g) was obtained through the globe thermometer technique applying the standard black globe. Comparing T-mrt values based on the six-directional technique but with different reference shapes revealed that the difference was always in the +/-5 degrees C domain. Of the cases, 75 % fell into the +/-5 degrees C Delta Tmrt range when we compared different techniques with similar reference shapes [T-mrt(sp) and T-mrt(T-g)] and only 69% when we compared the different techniques with different reference shapes [T-mrt(st) and T-mrt(T-g)]. Based on easily accessible factors, simple correction functions were determined to make the T-mrt(T-g) values of already existing outdoor thermal comfort databases comparable with other databases which involve six-directional T-mrt. The corrections were conducted directly between the T-mrt(T-g) and T-mrt(sp) values and also indirectly, i.e., by using the values of T-g to reduce the differences between T-mrt(sp) and T-mrt(T-g). Both correction methods resulted in considerable improvement and reduced the differences between the T-mrt(sp) and the T-mrt(T-g) values. However, validations with an independent database from Hungary revealed that it is not suggested to apply the correction functions under totally different background climate conditions.