Fethi Albouchi

Estimation of radiative and conductive properties of a semitransparent medium using genetic algorithms

The aim of this work is to simultaneously identify the conductive and radiative parameters of a semitransparent sample using a photothermal method associated with an inverse problem. The identification of the conductive and radiative proprieties is performed by the minimization of an objective function that represents the errors between calculated temperature and measured signal. The calculated temperature is obtained from a theoretical model built with the thermal quadrupole formalism. Measurement is obtained in the rear face of the sample whose front face is excited by a crenel of heat flux. For identification procedure, a genetic algorithm is developed and used. The genetic algorithm is a useful tool in the simultaneous estimation of correlated or nearly correlated parameters, which can be a limiting factor for the gradient-based methods. The results of the identification procedure show the efficiency and the stability of the genetic algorithm to simultaneously estimate the conductive and radiative properties of clear glass.

Optimal experiment design and thermo-physical characterization of a plastically deformed solid

The thermo-physical properties of a plastically deformed solid are measured using a non-destructive photo-thermal method. The experiment is optimally designed in order to choose the optimal heat flux duration, the sample thickness and the thermocouple position. The thermo-physical properties of the deformed sample are then identified by minimizing the sum of squares of the differences between experimental measurements and numerical results of a 2D model describing the heat transfer in the cylindrical sample. These identification results are finally compared with standard thermal diffusivity measurements (isotropic model) made on both initial and deformed samples.

Analysis of differential scanning calorimetry data of the paraffin/graphite waste composites for thermal energy storage

A paraffin/graphite waste composite for thermal energy storage at low temperature was elaborated using the cold uni-axial compression technique and its thermal energy storage properties were studied versus percentage of graphite waste using differential scanning calorimetry (DSC). Results indicated that the phase transition temperature did not change with a change in the amount of paraffin, whereas the latent heat of phase change was decreased with increasing graphite waste content. Also, the effect of the graphite addition on the thermal conductivity of the composites was investigated using the periodic temperature method.