Diffusion welding in gradient heatmetry

Gradient heatmetry allows you to record, process and analyze pulsations of heat flux, which is of paramount importance in the research of gas flow around bodies, in the study of complex heat transfer, etc.

A simplified model for calculating heat transfer through the double skin facade

Double skin façade (DSF) has been recognized as a flexible type of envelope that can adapt to various building needs, such as insulation, solar heat gain, ventilation, and shading. This adaption ability makes the DSF a potentially high performance envelope. However, the reliable calculation of the heat flow in the DSF has been a challenging task due to the complex heat transfer process involved in the DSF. In this study, we propose a simple model that aims to simplify the heat transfer calculation involved in the DSF. In this model, a characteristic function of heat transfer coefficient (CFHTC) was proposed for the heat transfer between the inner layer and the outside air, which would otherwise call the complex convective heat transfer in the cavity. We use experimental data to demonstrate that this function can be expressed as a function of the incident solar intensity. This CFHTC is supposed to be dependent on the geometry of the DSF. With the CFHTC, the calculation of the heat transfer between the inner layer of the DSF and the outside air is simplified and can be incorporated in energy simulation tools.

Optimal control of the radiation heat exchange equations for multi-component media

An analysis of optimal control problems for nonlinear elliptic equations modeling complex heat transfer with Fresnel conjugation conditions on the discontinuity surfaces of the refractive index is presented. Conditions for the solvability of extremal problems and the nondegeneracy of the optimality system are obtained. For the control problem with boundary observation, the bang-bang property is set.

A Non-Field Analytical Method for Solving Some Nonlinear Problems in Heat Transfer

This paper presents an extension of the non-field analytical method – known as the method of Kulish – to some nonlinear problems in heat transfer. In view of the fact that solving nonlinear problems is very complicated in general, the extension of the method is presented in the form of several important illustrative examples. Two classes of problems are considered: first are the problems, in which the heat equation contains nonlinear terms, while the second type of the problems includes some problems with nonlinear boundary conditions. From the practical viewpoint, the case considered in Section 4 is of the greatest interest. In that section, it is shown that, for complex heat transfer problems, where applications of the non-field method are practically impossible due to a large volume of necessary computations, it is still possible to analyse the solution behaviour and automatically determine similarity criteria for the limiting values of the parameters. Wherever possible the obtained solutions are compared with known solutions obtained by other methods. The practical advantages of the non-field method over other analytical methods are emphasised in each case.

Model of Complex Heat Transfer in the Package of Rectangular Steel Sections

During heat treatment of rectangular steel sections, a heated charge in the form of regularly arranged packages is placed in a furnace. The article presents a model of a complex heat transfer in such a package using the thermo-electric analogy. The model considers the following types of heat transfer: conduction in section walls, conduction and natural convection within gas, heat radiation between the walls of a section, as well as contact conduction between the adjacent sections. The results of our own experimental research were used for calculations of heat resistance applying to natural convection and contact conduction. We assumed that the material of sections was low-carbon steel and the gas was air. The result of the calculations of the presented model is total thermal resistance Rto. The calculations were performed for the temperature range 20–700 °C for four geometrical cases. Due to the variability of conditions for contact heat conduction, we assumed that total thermal resistance for a given charge is contained within a value range between Rto-min and Rto-max. We established that the value of Rto depends significantly on the section’s geometry. The larger the section sizes, the greater the changes of Rto. The minimal and maximal values of Rto for all packages were 0.0051 (m2·K)/W and 0.0238 (m2·K)/W, respectively. The correctness of model calculations was verified with the use of experimental data.