An Inverse Heat Transfer Problem Method For The Field Detection Of Wall Thermal Performance

In China,building energy consumption accounts for a large proportion of the total energy consumption,and the energy consumption caused by the envelope accounts for the highest proportion of building energy consumption.Field detection of thermal performance of building envelope is of great significance for building energy conservation.In view of the limitations of the existing field detection methods for thermal performance of building envelope,based on the frequency response of the method of harmonic response theory,two inverse heat transfer problem methods are put forward,which are used to solve the thermal conductivity and volume specific heat of single layer homogeneous wall and thermal inertia index of multi-layer wall according to the mathematical relation of output response,input signal and thermal system.First,the inverse problem methods are simulated and verified.Under the set heat transfer conditions,the inverse problem methods are used to solve the thermal conductivity and volume specific heat of three single-layer materials,as well as the thermal inertia index and characteristic value of heat accumulation of six walls composed of three different layers of materials in six different order,which shows that the inverse problem methods are completely feasible in theory to be used for solving monolayer and multilayer wall thermal performance index.At the same time,the concept of characteristic value of heat accumulation of multilayer wall is derived by analyzing the simulation results of multilayer wall.The characteristic value of heat accumulation is consistent with the physical meaning of the coefficient of heat accumulation of the single-layer wall,which reflects the heat storage characteristic of the multi-layer wall under the specific sequence of each constituent layer and specific structure.The thermal inertia index and characteristic value of heat accumulation of the multi-layer wall jointly determine the unsteady heat transfer characteristic of the wall.Then,under the experimental conditions,the inverse problem methods are used to detect the thermal performance of the fiber reinforced calcium silicate board and XPS extruded board with different thickness,as well as the solid brick wall with cement plaster on both sides.The results showed that the inverse problem methods could be used to detect the thermal performance index of the wall.Finally,the feasibility of the inverse problem methods is verified again through a field test example,and the specific process of the field application of the inverse problem methods is given.