Influence Research Of Thermal Physical Uncertainty On Heat Transfer Characteristics Of Composite Walls

The research on heat transfer characteristics of composite walls has always been one of the hot topics in the field of numerical heat transfer and building energy conservation.At present,almost all the related researches adopt deterministic mathematical models,physical parameters and boundary conditions.However,there are a lot of uncertainties in the actual heat transfer process,such as boundary conditions,physical parameters and so on.The influence of these uncertainties on the heat transfer process must be considered.In this paper,based on Monte-Carlo stochastic finite element method,the effects of stochastic distribution of boundary conditions and physical parameters on the heat transfer characteristics of composite walls are studied.The following conclusions are drawn:A Monte-Carlo stochastic finite element method is developed to solve the uncertainty propagation of heat transfer between a single-layer wall and composite walls under stochastic boundary condition and stochastic thermal conductivity.Firstly,the Karhunen-Loeve expansion of the input stochastic fields such as boundary condition and thermal conductivity is carried out and the stochastic samples of boundary condition and thermal conductivity are generated based on the Latin hypercube sampling method.Then,coupled with the stochastic finite element program of the steady-state heat conduction differential equation,the single-layer wall and the composite walls with stochastic boundary condition and stochastic thermal conductivity are numerically calculated.The average value and standard deviation of random temperature field are calculated by the sampling statistics method.Based on the above calculation algorithm and framework,a MATLAB stochastic finite element program is compiled to solve the heat transfer uncertainty of single-layer wall and composite walls under the uncertainty of boundary condition and thermophysical parameters.The influence of correlation length and variation coefficient of stochastic boundary condition and stochastic thermal conductivity on the uncertainty of heat transfer process of single-layer wall and composite walls is analyzed.The average temperature field shows that the average temperature fields of single-layer wall and composite walls are basically the same as that of deterministic condition,and the insulation performance of composite walls is better than that of single-layer wall.The probability distribution of characteristic node temperature under random boundary condition and random thermal conductivity basically shows normal distribution,and increases with the increase of correlation length and variation coefficient.The influence of variation coefficient on heat transfer performance of single wall and composite walls is stronger than that of correlation length.