Study On Building Envelope Comprehensive Thermal Performance Based On System Identification Theory

Building is a synthesis of many components. There are walls, windows, doors. The methods and level of construction have an important impact on insulation and energy saving. At present, heat flow meter method and heat box method are all steady state methods, which are used in domestic and international. These methods can only measure a single heat transfer coefficient, and can not measure overall envelope thermal performance through the construction and installation.Given the current heat transfer coefficient testing instrument is not comprehensive, using transfer function theory and system identification theory, by measuring the thermal response of building envelope characteristics, can we calculate the integrated heat transfer coefficient envelope in order to determine whether the buildings meet energy requirements. The focus of this method is not a single envelope, but the entire envelope and its integrated construction technology.According to system identification theory, the mathematical model of heat transfer process is established. In order to facilitate solving the model, model parameters from all aspects of the process through simplification, identified as the single input, single output, linear, constant, random system model. On the basis, the envelope compressive heat transfer coefficient formula is deduced. Because of the limit of experiment conditions, the experiment is done in the " experiment room", by the time the object recognized are wood board and gypsum board; the input is heat power and output is temperature difference between indoor and environment of the " experiment room".The results show that the model output and measured output fit best, so the model is reliable. To further prove the reliability of this method then the heat flow meter method is used to verify, and then the compressive heat transfer coefficient is calculated. The comparison of two methods results shows that the compressive heat transfer coefficient results calculated by means of system identification reaches a certain degree of accuracy; the maximum error between the two methods is only 2.27%. Therefore, in view of experimental measurements and theoretical analysis methods are relatively simple. The test method of calculation of envelope compressive heat transfer coefficient based on system identification theory can be direct promoted in engineering practice.