New Approach and Alternate Criterion for Heat-transfer Analysis of Building Walls and Its Applications

Abstract

Energy consumed by buildings accounts for approximately one-third of the total energy consumption of the society. Moreover, energy systems employed in buildings emit hazardous pollutants, such as, NOx, PM2.5 and CO2, into the environment. Consequently, increasing the energy efficiency of buildings constitutes an important problem concerning the field of building-energy and environment conservation. Thermal resistance and capacitance are two important thermophysical properties of building walls significantly impacting their heat-transfer performance. Traditional theories concerning these properties, however, face certain limitations: (1) the concept of thermal resistance is only valid for one-dimensional, steady heat conduction without existence of an internal heat source; (2) thermal resistance and capacitance are relevant, and can, therefore, not be used to analyze heat-transfer and storage performance, respectively, of building walls. Based on the entransy-dissipation-based impedance theory, a new approach towards realization of heat-transfer analysis and optimization has been proposed in this study. The weightiness of thermal resistance and capacitance with regard to heat-transfer performance has been described along with deduction of the corresponding substitutional relation via illustrative examples. The proposed approach has been demonstrated to effectively overcome aforementioned limitations of building energy conservation problems.