Analysis Method Based On System Identification Theory Of Unsteady Heat Transfer Of Multi-layer Wall

With the advance of society and the improvement of people's living standard, the demand to man-made environment has becoming increasingly strict. The exact prediction of space load can assure the indoor environment quality, and is beneficial to promote energy conservation. As a large proportion of total space load, the space load resulting from transient heat conduction of building envelope is difficult to calculate exactly. The direct root-finding method, as a conventional method for analyzing transient heat conduction of wall, will produce much inevitable problem such as root-missing and low efficiency. At all times, people quested for more efficient and simple method to analyze its dynamic heat conduction.It will present a new method-frequency-domain regression (FDR) method based on system identification theory for calculating transient heat flux through multi-layer walls. First, the frequency characteristics of the total transmission matrix are calculated within the frequency range concerned. Then, a simple polynomial 5-transfer function is yielded from the theoretical frequency characteristics for internal, cross and external heat conduction by applying appropriate identification algorithm, respectively. Finally, the wall response factors are obtained simply by applying inverse Laplace transforms on the polynomial s -transfer function, and conduction transfer function coefficients are obtained by applying Z-transforms. Compared to other ways, FDR method is very simple and efficient, and has high accuracy and fast computation speed.For the need of architecture design, it appears more and more cylindrical walls and semi-spherical roofs. However, current space load-predicting programs do not account for the effect of dynamic heat conduction for above two constructions on indoor space load. In order to improve current space load-predicting and energy-consuming program, transfer matrix of cylindrical and spherical constructions are deduced using Laplace transform. Considering complexity of transfer functions for above both constructions, conventional methods are difficult to proceed and can't assure computation exactness and efficiency, FDR method is adopted. The comparisons and validations show that the analysis for transient heat conduction of cylindrical and spherical constructions is also simple and efficient, as long as the FDR method is used.