Papers by Keyword: Heat Diffusion

Abstract: In pursuit of greater practicality in the food preparation, in recent years there has been a considerable growth of researches in the field of cooling and freezing of food. Therefore, the trade in frozen food has been very promising, allowing a great variety of products to the consumers due to the convenience of transportation, storage and use. Cooling and freezing of products are preservation methods used in the food industry to maintain the sensorial attributes and nutritional properties of these products. In this sense, in order to optimize the process and reduce energy costs, this work presents a transient three-dimensional mathematical modeling to describe the heat transfer inside liquid materials with parallelepiped shape including phase change (liquid-solid) term. The governing equation was solved numerically using the finite volume technique with a fully implicit formulation. As an application, the methodology was used to predict heat transfer during cooling, freezing and post-freezing of the Tahiti lemon pulp. Numerical results of the temperature distribution at different process instants are presented and analyzed, and temperature data at the center of the product throughout time were compared to experimental data reported in the literature and a good agreement was obtained.

Abstract: An analytical approach of transient heat conduction in a two layered material, in finite dimensions within imperfect thermal contact, subjected to a moving Gaussian laser beam was achieved. The result of this study allows on the one hand an easy access to the distribution and the evolution of the temperature in both layers of the workpiece; on the other hand permits to clarify the influence of the contact quality on the temperature gap at the interface. The effect of a porous grannular deposit layer was also considered in this study. A design of electronic tracks by laser cladding was studied as an application example in the surface treatment area; this model can be also used to estimate the thermal contact resistance between layers.

Abstract: Recent developments in infrared camera technology, testing methods and data processing algorithms have brought significant progress for high resolution spatial and temporal analysis of thermal radiation. Together with industry standard automation technology and specific infrared image data processing it became possible to non destructively inspect laser welded seams and other types of joints using heat flux analysis subsequent to thermal stimulation. High thermal diffusion coefficients of the usually metallic samples under test make the availability of high-speed infrared cameras as a key hardware component indispensable. Since high-speed infrared cameras with frame rates of at least 500 Hz have become available for commercial applications, non-destructive testing systems with a new class of performance were designed, manufactured, and implemented at industrial sites. Heat flux analysis as a new and robust method of non-destructive testing has been implemented for various types of equipment, ranging from off-line tools for laboratory use to automated robot based systems enabling fast and operator-free in-line inspection. Depending on environment, implementation surroundings, and geometry of objects to be inspected, different types of pulsed or continuous operating heat sources (e.g. flash light, laser, … ) are selected. Due to its outstanding industrial relevance non-destructive testing of laser welded seams in automobile manufacturing is shown in detail in this paper.