Human thermal comfort in non-uniform thermal environments: A review

Thermal comfort is critical for ensuring the health and productivity of occupants and knowing their thermal demand could help creat a satisfying environment with the least energy waste. Theory of thermal comfort is built based on experimental studies in uniform and stable environments, while there is still a gap when applying in evaluating human thermal comfort in non-uniform thermal environments. Therefore, an insight into human thermal comfort in non-uniform thermal environments is taken. The fundamental studies of thermal comfort in non-uniform thermal environments are explicated, including thermal comfort theory applied in non-uniform thermal environments, types of non-uniform thermal environments and corresponding studies, physiological and psychological thermal responses in the environments. Besides, the evaluation indices of non-uniform thermal environments are classified according to their definitions and the comfort models are reviewed. Finally, future works in this research field are discussed. In general, the overall thermal comfort and local thermal comfort should be both taken into account in non-uniform thermal environments where skin temperatures and psychological thermal responses of occupants are different among local body segments. Moreover, as studies of local thermal comfort are mainly conducted in thermally neutral condition, the limits considering the state deviating thermal neutrality (slightly warm or cool), which is frequently found in reality, are encouraged to be studied. Finally, a well-defined comprehensive index should be proposed considering heat exchange of human body with their microenvironments and thus the comfort range of the index could be provided for designing of non-uniform thermal environments.