Analysis of turbulent wall jet impingement onto a moving heated body

Purpose The purpose of this study is to make a numerical analysis of a wall jet with a moving wall attached with a heated body. The hot body is cooled via impinging wall jet. Thus, a jet cooling problem is modeled. The Reynolds number is taken in three different values between 5 × 103 ≤ Re ≤ 15 × 103. The h/H ratio for each value of the Re number was taken as 0.02, 0.04 and 0.0, respectively. Design/methodology/approach Two-dimensional impinged wall jet problem onto a moving body on a conveyor is numerically studied. The heated body is inserted onto an adiabatic moving wall, and it moves in +x direction with the wall. Governing equations for turbulent flow are solved by using the finite element method via analysis and system Fluent R2020. A dynamic mesh was produced to simulate the moving hot body. Findings The obtained results showed that the heat transfer (HT) is decreased with distance between the jet outlet and the jet inlet. The best HT occurred for the parameters of h/H = 0.02 and Re = 15 × 103. Also, HT can be controlled by changing the h/H ratio as a passive method. Originality/value Originality of this work is to make an analysis of turbulent flow and heat transfer for wall jet impinging onto a moving heated body.

OPTICAL-ELECTRONIC INSTRUMENT FOR MEASURING THE RADIATION COEFFICIENT AND TEMPERATURE OF THE CONTROLLED OBJECT

The operating principle of optoelectronic instruments for measuring the temperature of the heated products based on the measurement of the radiation flux from the heated product, which depends on the temperature and emissivity of the surface material. The main error of such optocal-electronic devices is the methodological component, which is due to the variability of the radiation coefficient of the surface of the product material. The radiation coefficient of an object depends on the material, the surface state of the material, and the temperature. In the measurement process, it is difficult to take this dependence into account, since there are no exact analytical expressions of these dependencies. In practice, the radiation coefficient of the surface of material the product is determined approximately using reference books. For a more accurate determination of the radiation coefficient, a preliminary study is necessary, which requires more complex equipment than a device for measuring the radiation flux from a heated body. To solve this problem, there are empirical generalized equations of the functional dependences of the radiation coefficient. The article analyzes the errors in determining the radiation coefficient using generalized equations in comparison with experimental data. The analysis indicates that the error in determining the radiation coefficient can reach large values that may not meet the requirements of consumers. To improve the accuracy of measuring the temperature of the object, a device has been developed that implements the method of sample signals. The developed device predetermines the radiation coefficient of the measured product at a certain temperature and introduces a correction when measuring the temperature.

THERMAL IMAGING STUDIES OF THE ORIGINAL HEAT EXCHANGER PLATE

A modern method for studying the temperature field of heated bodies is considered. The object under study is a corrugated heat exchange plate with an original geometry. Heat exchangers are one of the main types of process equipment in heat supply systems. The article presents a comparison of two main types of heat exchange equipment: shell-and-tube and plate devices. The FLIR i50 thermal imaging device is characterized. A comparison is made between a standard heat exchange plate and a corrugated plate with spherical recesses located linearly on the areas between the corrugations. The use of original plates can increase the efficiency of the heat exchange process due to increased turbulization of the coolant. The relationship between the true temperature of a heated body and the brightness temperature of a black body is established. Experimental studies are carried out, in result the value of the average temperature of the heated body is obtained. This value is necessary for further calculation of heat transfer coefficients, which, in turn, are decisive in calculating the main parameter that characterizes the efficiency of heat exchange equipment-the heat transfer coefficient. The use of thermal imaging is the original way to study heat transfer processes, allowing to show the real increase of heat transfer coefficient of a plate heat exchanger.

Analisys of thermal processes during induction surfacing

Aspects of thermal phenomena associated with the production process of bimetallic billets in conditions of small penetration depths of eddy currents compared to the size of the heated body are considered. Various conditions of heat distribution in the heated layer and its removal are modeled using differentiated thermal resistance. Based on the analysis of the temperature distribution in various situational variants, promising ways to improve this technology are identified.

Real time optimization of temperature field in induction heating

Many induction heating processes must be controlled in accordance with the prescribed time evolution of temperature of the heated body (bodies). This requires a correct setting of field currents (amplitudes and frequencies) in the heating inductors that can vary either continuously or by steps. The paper presents a novel model of induction annealing of cylindrical aluminum billets based on solution of nonstationary forward and inverse tasks. The methodology is described in detail and illustrated with a typical example. Some of the results were verified experimentally.

Investigation of the Possibility for Control of High-Temperature Synthesis of Nanomaterials

The feasibility of creating conditions for control of high-temperature synthesis (SHS) of nanomaterials has been studied. Experiments were carried out to determine the velocity of the combustion wave propagation of aluminum nanopowder obtained by electric explosion. In the course of the study, the factors influencing formation of the induction time: the thermal diffusivity of the substrate, the method of initiation of the combustion wave (flame, spark, heated body), the induction time between the initiating front and the front of the thermal explosion were considered. The relation describing the time of induction of thermal explosion is established.

Analysis of Natural Convection Flow in a Trapezoidal Cavity Containing a Rectangular Heated Body in Presence of External Oriented Magnetic Field

The laminar natural convection flow and heat transfer inside a trapezoidal cavity filled with air and containing a rectangular block is investigated numerically. The left and right walls of the cavity are cold, the top and bottom walls are adiabatic and the rectangular body is heated uniformly. Finite Element Method of Galerkin’s weighted residual scheme is used to solve the transport equations with appropriate boundary conditions. The main objective of this study is to explore the influence of pertinent parameters such as Rayleigh number, Hartmann number and orientation of the magnetic field on the flow and heat transfer performance of the fluid while the Prandtl number is considered fixed. Results indicate that the heat transfer rate is significantly affected by increasing the mentioned parameters.

SIMULATION OF RADIATIVE HEAT FLUX DISTRIBUTION UNDER AN INFRARED HEAT EMITTER

<p>The article deals with a heat radiation model used for heat flux calculation of an infrared heater. In general, we consider a system consisting of a set of objects, whereas a single object could stand for a heater, a reflector or a heated body. Each of the objects is defined by its bounding surface. The presented model applies a 2D restriction of the real system. The aim of a particular simulation is to obtain a heat flux distribution all over the heated body under given conditions such as objects temperature and material properties. Furthermore, the implemented model is used to design a reflector profile to obtain a desired heat flux distribution. The paper presents the implemented model, a comparison of simulated and measured data and an example of reflector design.</p>