Search

Numerous metrics and indices have been proposed for the assessment of thermal perception and comfort. Commonly used indices based on the estimate of the heat flow between the human and its environment includes the well-known Fanger's method, also known as the PMV-PPD thermal comfort model. Recently this thermodynamic approach has been expanded with the application of the second law of thermodynamics. In this paper, an exergy-based analysis of the relation between the human and its environment is presented. Heat and mass flow rate due to convection, radiation, evaporation and respiration are calculated and expressed in terms of exergy loss. This value is used in the modified Fanger's thermal comfort model, where the heat balance equation is replaced by the exergy loss. The paper builds upon prior studies on determination of internal and external exergy losses by revised and newly defined formulas taking into account clothing and indoor conditions. The results quantitatively show that thermal energy load in the original Fanger's PMV model could be substituted by exergy loss and it corresponds to a certain level of subjective assessed thermal comfort level. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes the application of exergy analysis to human heat and mass exchange with the indoor environment. The basis for this paper is the existence of a formal similarity between the parameters defining human heat and mass transfer governed by physiological processes and the parameters defining exergy destruction. Basic heat and mass transfer is calculated using a standard two-node human physiological model. To enable an exergy analysis the model was divided according to heat and mass transfer over appropriate boundaries. The exergy analysis was performed for each process with regard to the type of exergy that participates in heat and mass exchange with respect to the indoor environment. The results provide insight into the complex interactions between the human body and environment as characterized by exergy destruction. Furthermore, the analysis indicates that at given physiological parameters only a certain combination of environmental conditions ensures minimal exergy destruction. These environmental and human conditions coincide with expected level of thermal comfort. [ABSTRACT FROM AUTHOR]