Calculating method for the conduction z-transfer functions of multilayer walls based on system identification

Frequency domain regression (FDR) method was developed to calculate z-transfer functions of multilayer walls. This method is based on the theoretical frequency characteristics of transient heat conduction through a multiplayer wall to estimate a simple polynomial s-transfer function. The simple polynomial s-transfer function is equivalent to the hyperbolic s-transfer function of the wall in terms of frequency characteristics. First, the frequency characteristics of transient heat conduction of the wall were calculated within the frequency range concerned. Then, a set of linear equations was solved to yield a simple polynomial s-transfer function for internal, cross and external heat conduction. Finally, z-transfer functions were obtained by applying z-transforms on the time-domain response of the polynomial z-transfer function. The comparisons and validations show that this method is simple, efficient, fast and accurate.