An inverse problem based on genetic algorithm to estimate thermophysical properties of fouling

Abstract

In the past few decades, the study on how to apply genetic algorithms to problems in the industrial engineering world has aroused a great deal of curiosity of many researchers in the area of management science, industrial operations and engineering systems. This paper shows an experimental process of thermophysical properties estimation of fouling deposited on internal surface of a heat exchanger tube using genetic algorithms. In brief, the deposits on heat exchanger tubes are caused by the presence of inorganic salts, of small quantities of organic materials and products of corrosion in the water. From thermophysical point of view, the deposited fouling has harmful effects on the heat exchanger efficiency. For these reasons the determination of its thermophysical properties became very important. The experimental bench using a photothermal method with a finite width pulse heat excitation is used. The genetic algorithm is used to minimize an objective function containing a calculated and a measured temperature. This last is measured on the rear face of a bi-layer system composed of a section of a heat exchanger and the fouling deposited on during and after a finite width pulse heat excitation on its front face. The calculated temperature, that is a function of the unknown thermophysical properties of the bi-layer system, is calculated by the resolution of the one-dimensional linear inverse conduction problem, and by the use of the thermal quadrupoles formalism. The motivation in using genetic algorithms was their potential to overcome the restriction to the estimation of non-correlated parameters of gradient-based methods, and their powerful ability to work well for many complex problems which are very difficult to solve by conventional techniques. The results of the estimation procedure show on the one hand the efficiency and the stability of the developed genetic algorithm to estimate the thermophysical properties of fouling and the high accuracy of the obtained results on the other hand.