Measurement of the black globe temperature to estimate the MRT and WBGT indices using a smaller diameter globe than a standardized one: Experimental analysis

Abstract

Heat stress can affect negatively human performance, behavior and even health, therefore, mean radiant temperature (MRT) and wet-bulb globe temperature (WBGT) measurement and monitoring should be obtained for any environment in which people are constantly exposed. The aim of this work is to compare the globe thermometer temperature (tg), used for calculating both MTR and WBGT, using a smaller globe compared to a standardized diameter. For such purpose, a prototype has been designed. The device consists of an Arduino MEGA board, three temperature sensors, two black globes (Copper globe, matt black painted) and an anemometer. As an effort to use a device with a globe easier to handle in a real measuring device, a 9 cm diameter globe has been used which has a smaller diameter than a standardized one (15 cm); the third temperature sensor is used to measure the air temperature. MRT monitoring tests were carried out using the proposed prototype, collected data were compared between the smaller and the standardized diameter globes measurements according to UNE EN ISO 7723 and NTP 322 recommendations. Results of this work show that it is possible to use a smaller diameter globe in a heat stress monitor, with an acceptable margin of error compared to a standardized size globe.