Resolving indoor shortwave and longwave human body irradiance variations for mean radiant temperature and local thermal comfort

A spatially and directionally resolved longwave and shortwave radiant heat transfer model is presented via a series of experiments in a thermal lab to input surface temperatures and geometries, as well as skin temperature readings from a human subject, in order to test mean radiant temperature (MRT) and thermal comfort results for the person. Combining novel scanning and thermography methods together with ray-tracing simulation, high-resolution thermal models are derived fully characterizing the longwave and shortwave radiant heat fluxes in space and resolving the impact of these variations on MRT. The study demonstrates the significant amount of spatial variation of both shortwave and longwave radiant heat transfer on MRT through the room and also across body segments: the experimental results show variations of up to 14.5°C across the room, leading to PMV comfort variations from −0.27 to 2.45, clearly demonstrating the importance of mapping the entire radiant field rather than assuming one MRT value for a thermal zone. Furthermore, local radiant temperature, newly defined Body Segment Plane Radiant Temperature (BSPRT), variations across the body of more than 30°C are found. Finally, a detailed human thermo-physiology model was used to evaluate the possible variation in thermal sensation between the different body segments due to the large differences in local MRT.