Physiological Indicators of Thermal Comfort: A Comprehensive Approach Using the Metabolic-Based Predicted Mean Vote Index

Abstract

Current thermal comfort constructs are perceptional, and their relationships to the physiological responses are not fully understood. The latter are very important, not only to indicate personal comfort perception but also to protect personal health against cold and heat stresses. This paper combined a two-node bioheat model with the metabolic-based predicted mean vote index (MPMV) to uncover the relationships between the physiological responses and perceptional thermal sensation at steady-state conditions. The MPMV index accounts for sweating and non-shivering thermogenesis (NST) at the neutral comfort state and handles both core and skin cooling cases. Simulations were conducted for adults in typical indoor environment conditions. The physiological responses investigated included the body, core and mean skin temperatures, skin evaporative heat flux, shivering metabolic rate, and skin blood flow. The study revealed that only the mean skin temperature and skin blood flow can discriminate between comfort perception levels and can therefore be used alone or combined with other variables as alternative physiological indicators. The comfort range (MPMV within ±1) in terms of the mean skin temperature is maintained by regulatory sweating and/or NST and gets wider with increasing activity levels. The study also offered important insights for practical applications and future research.