Measurement of ambient air temperature for evaluation of human heat convective losses

To analyze a human being’s local thermal balance through simulation and/or experiments, a good description of the thermal environment is indispensable. Many local physical data are needed to calculate the heat exchanged by the body during transient conditions in a non-homogeneous environment. To evaluate the conditions near the body, measurements have to be made very close to the surface in extremely non-homogeneous thermal conditions, so sometimes the probes have to be fixed on the subject himself. For air temperature measurements, ISO recommends protecting the probe by a low-emissivity protective screen and increasing air velocity that is not possible as it will change heat exchanges on skin surface. If air velocity is low when the air is colder than the surrounding surfaces, the air temperature measured close to the body is overestimated. We performed laboratory experiments to understand the influence of the protective screen. It appeared that the screen and the aerodynamic flow in and around the screen influenced the temperature of the probe. The paper quantifies the correction needed to improve measurements, and the discussion leads to recommendations about how to measure air temperature close to a human being.