Identifying neutral thermal conditions of driver body segments in vehicle cabins using a coupled thermophysiological and thermal comfort model

Abstract

A highly asymmetric and nonuniform thermal environment frequently encountered in vehicle cabins can lead to thermal discomfort for drivers. Understanding the segment‑specific thermal neutrality of the driver is therefore essential for the energy‑efficient design and control of vehicle HVAC systems. In this study, a coupled thermophysiological and thermal comfort model was developed to identify the neutral thermal conditions of individual body segments for a driver in a vehicle cabin. Various nonuniform thermal environments measured in a real vehicle cabin were applied to quantitatively analyze the relationships among segmental heat loss, skin temperature, and thermal responses. Significant differences in heat loss among body segments were observed even under the same operative temperature due to variations in clothing insulation, metabolic rate, heat transfer coefficients, and skin temperature. Optimal heat loss values corresponding to neutral thermal sensation ranged from 37.1 W/m² to 124.0 W/m², depending on the body segment and season. These optimal values provide a quantitative basis for segment‑specific thermal management and offer practical guidance for the design and control of vehicle HVAC and personal comfort systems.