Simultaneous estimation of the thermophysical properties of liquids and of the boundary conditions

The determination of thermophysical properties from an inverse method is an attractive technique both from the experimental and methodological point of view. The aim of this paper is to identify simultaneously the thermal conductivity and the thermal diffusivity of liquids and the heat transfer coefficient by the utilization of the well-known flash method which is coupled to an inverse parameter identification method. To be characterized, a thin layer of the liquid is sandwiched between two metal plates and a cylindrical sample holder. Then it is subjected on its front face to a heat flux density during a short time. The temperature evolution of the rear face of the container is measured during and after the thermal excitation. The identification procedure based on the inverse method consists in the minimization of an objective function that represents the errors between the measured temperature at the rear face and a theoretical model that describes the temperature evolution of the system (liquid and container). The theoretical model, which is a function of the unknown thermophysical properties of the three layer system, is calculated by the use of the thermal quadrupoles formalism. To minimize the objective function, a genetic algorithm is developed and used. Genetic algorithm is categorized as global search heuristics. It is an iterative procedure which borrows the ideas of natural selection and survival of the fittest from natural evolution which were first described by Darwin.The identification procedure based on the use the flash method and the developed genetic algorithm is used in this work to identify thermophysical properties of distilled water, glycerol, acetone, and ethylene glycol. A good agreement is found between our experimental results and the thermophysical properties indicated in the literature of the studied liquids.

► Estimation of thermal conductivity and thermal diffusivity of liquids and heat transfer coefficient.
► Development of a mathematical model based on the thermal quadrupole formalism.
► Use of an inverse heat transfer problem based on genetic algorithm to estimate these correlated properties.