scholarly journals Influence of Heat Exchange Coefficients on Both Optimized Thermal Contact (OTCR) and Critical (CTCR) Resistances at the Contact Interface of a Flat Concrete Slab and a Rice Straw Board

2021 ◽  
Vol 13 (12) ◽  
pp. 392-402
Author(s):  
Alassane Diene ◽  
Mamadou Lamine Lo ◽  
Abdoulaye Sene ◽  
Ablaye Fame ◽  
Youssou Traore ◽  
...  
Keyword(s):  
Heat Exchange ◽  
Rice Straw ◽  
Concrete Slab ◽  
Thermal Contact ◽  
Contact Interface

scholarly journals Study on non-stationary heat exchange in combined packages of water-resistant protective clothing of firefighters

2020 ◽  
Vol 64 (4) ◽  
pp. 467-476
Author(s):  
A. I. Ol’shanskii ◽  
R. V. Okunev ◽  
A. M. Gusarov
Keyword(s):  
Thermal Conductivity ◽  
Heat Exchange ◽  
Protective Clothing ◽  
Thermal Contact ◽  
Exchange Process ◽  
Toxic Substances ◽  
Nonlinear Transport ◽  
Stationary Heat ◽  
Technical Requirements ◽  
Linearization Methods

The results of research of non-stationary heat exchange in combined packages intended for creation of special water- and heat-resistant protective clothing of firefighters from dangerous and harmful factors during emergency rescue and other urgent works, with participation of non-toxic substances, acid solutions, alkalis, oil and petroleum products, liquid toxic substances, as well as during operation in water with temperature from 0 to 70 °С are presented. The stability of clothing material packs has been investigated as a transient heat exchange process in a multilayer plate with ideal thermal contact at the joints of the layers. The unlimited plate is heated on both sides under different heat exchange conditions according to Newton’s Law, with constant action of the heat source on one of the surfaces of the hot liquid contacting through the waterproof thin surface. Second surface of the plate interacts with external medium, temperature of which varies according to linear law. At solving the equation of non-stationary thermal conductivity with nonlinear transport coefficients, linearization methods are used based on the approximation of nonlinear coefficients, such that nonlinear equations become approximately linear. The entire heat transfer process is divided into a plurality of small-time intervals within which the transfer coefficients are constant. The zonal method of investigation of non-stationary thermal conductivity in clothing packages establishes equations for calculation of temperature, densities of thermal flows, distribution of temperature across thickness of clothing packages. It has been shown that under accepted calculation simplifications, parameter values are well consistent with the experiment. The composition of the clothing package is proposed, which meets the technical requirements of TУ BY 101114857.082-2015 “Personal Protective Kits”.

scholarly journals Thermal condition of cohesion in a two-layer roll of a rolling mill

2019 ◽  
pp. 45-48
Author(s):  
Olga Panteleivna Demyanchenko ◽  
Viktor Lyashenko
Keyword(s):  
Heat Exchange ◽  
Temperature Distribution ◽  
Heat Conductivity ◽  
Rolling Mill ◽  
Thermal Condition ◽  
Thermal Contact ◽  
Homogeneous Equation ◽  
Target Setting ◽  
Radial Section ◽  
Ideal Thermal Contact

A condition of heat exchange between the layershaving different thermalphysic properties in a two-layercylindrical roll of a rolling mill is analyzed foe an ideal thermalcontact. It can be realized with application of the condition ofheat balance of one of the layers in the cylindrical area for ahomogeneous equation of heat conductivity. Analyzed was asimplified target setting in the radial section with a supposition,regarding an averaged in radius temperature distribution in theouter layer. By applying the condition of the thermal balance andby integrating the homogeneous equation of heat conductivity inthe two-layer area a condition of cohesion of an impedance typein case of an ideal thermal contact between the layers wasconstructed.

Development of an Experimental Procedure for Thermal Contact Resistance Estimation at the Glass/Metal Contact Interface

2013 ◽  
Vol 6 (2) ◽  
Author(s):  
B. Abdulhay ◽  
B. Bourouga ◽  
F. Alzetto ◽  
C. Challita
Keyword(s):  
Heat Flux ◽  
Contact Resistance ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Thermal Conditions ◽  
Metal Contact ◽  
Contact Interface ◽  
Equivalent Thermal Conductivity ◽  
Experimental Procedure ◽  
Glass Metal

In this paper, an experimental device is designed and developed in order to estimate thermal conditions at the glass/metal contact interface. This device is made of two parts: The upper part contains the tool (piston) made of bronze and a heating device to raise the temperature of the piston to 700 °C. The lower part is composed of a lead crucible and a glass sample. The assembly is provided with a heating system, an induction furnace of 6 kW for heating the glass up to 950 °C. The developed experimental procedure has permitted the estimation of the thermal contact resistance (TCR) using a developed measurement principle based on the inverse technique developed by Beck et al. (1985, Inverse Heat Conduction: III Posed Problems, Wiley Inter-science, New York). The semitransparent character of the glass has been taken into account by an additional radiative heat flux and an equivalent thermal conductivity. After the set-up tests, reproducibility experiments for a specific contact pressure have been carried out. Results show a good repeatability of the registered and estimated parameters such as the piston surface temperature, heat flux density, and TCR. The estimated value of TCR reaches 2 × 10−3 K m2/W with a maximum dispersion that does not exceed 6%.

scholarly journals SIMULATION OF HEAT EXCHANGE IN A MULTILAYER FLAT STRUCTURE UNDER PERFECT THERMAL CONTACT IN FIRE CONDITIONS

Fire Safety ◽  
2020 ◽  
Vol 36 ◽  
pp. 115-120
Author(s):  
R. Tatsii ◽  
M. Stasiuk ◽  
O. Pazen
Keyword(s):  
Thermal Conductivity ◽  
Heat Exchange ◽  
Thermal Contact ◽  
Internal Heat ◽  
Nonstationary Temperature ◽  
Heat Sources ◽  
Conductivity Equation ◽  
Flat Structure ◽  
Temperature Changes ◽  
Internal Heat Sources

The proposed work is devoted to the application of the direct method to the study of heat transfer processes in a multilayer flat structure. It is assumed that each layer is made of isotropic material of different thickness. There is an imperfect thermal contact between them, and the layers have internal heat sources. In this case, the isothermal surfaces are parallel planes, i.e the temperature changes in only one direction. On the outer surfaces of the structure there is a convective heat exchange with the environment, i.e the boundary conditions of the third kind are fulfilled. The coefficients of the thermal conductivity equation are considered to be piecewise constant with respect to the spatial coordinate. This is the first time the problem has been solved in this setting. The solution of the problem is realized by applying the method of reduction using the concept of quasi-derivatives and applying the theory of systems of differential equations with impulse action. The following is the procedure for separating Fourier variables using a modified method of eigenfunctions.Based on the physical content of the problem, the differential equation of thermal conductivity was written in the Cartesian coordinate system, but the solution scheme presented here without any fundamental difficulties extends to similar problems for multilayer bodies of basic geometric shapes by switching to appropriate coordinate systems. To illustrate the proposed method, a model example of finding the distribution of a nonstationary temperature field in a seven-layer flat structure under the influence of the hydrocarbon temperature of the fire is solved. The condition of ideal or non-ideal thermal contact is fulfilled between two adjacent layers. In addition, some layers have internal heat sources. The results of the calculations are presented in the form of a graph of temperature changes depending on timeand spatial coordinates.

scholarly journals Heat exchange of a roller with a particle from polymeric material when it is pressed into tissue

2019 ◽  
Vol 298 ◽  
pp. 00086
Author(s):  
Vladimir Fedyaev ◽  
Valentin Khaliulin ◽  
Marat Faskhutdinov ◽  
Alexey Belyaev ◽  
Liliya Sirotkina
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Initial Conditions ◽  
Thermal Contact ◽  
Polymer Particle ◽  
Heat Propagation ◽  
Conductive Heat ◽  
Polymer Particles ◽  
Heat Conservation ◽  
The Heat Balance

We study the heat transfer of polymer particles with a roller that presses the material of the particles into the fabric. Provided that the speed of movement of the tissue with the particles relative to the roller is small, the heat exchange of the pressed particles with the environment is not taken into account, a mathematical model of conductive heat transfer in the contacting roller, polymer particle and reinforcing fabric is proposed. This model includes heat conservation equations written with respect to average temperatures of the roller, particles, fabric, as well as boundary and initial conditions. Assuming that there is perfect thermal contact between the polymer particles and the fabric, in the direction of heat propagation the average thickness of the pressed tissue particle is small, the layer of material of particles and fabric is considered thermally thin, the temperature in it varies slightly in thickness. As a result, the initial system of three equations is reduced to one equation with respect to the temperature of the roller, which is supplemented by the corresponding boundary and initial conditions. In the case when the temperature along the radius of the roller varies along its radius linearly, the specific heat flux on the surface of the roller is estimated. After that, this expression is substituted into the heat balance equation of a thermally thin layer consisting of particle material and tissue, which is integrated after certain transformations.

The Use of Analog Computers for Determining Surface Parameters Required for Prediction of Thermal Contact Conductance

1964 ◽  
Vol 86 (4) ◽  
pp. 543-550 ◽  
Author(s):  
J. J. Henry ◽  
H. Fenech
Keyword(s):  
Experimental Data ◽  
Unit Area ◽  
Thermal Contact ◽  
Analog Computer ◽  
General Purpose ◽  
Thermal Contact Conductance ◽  
Average Thickness ◽  
Contact Interface ◽  
Contact Conductance ◽  
Surface Profiles

The mathematical analysis of a thermal contact by Fenech and Rohsenow requires knowledge of certain parameters describing the geometry of the contact interface. These parameters are volume average thickness of the void above and below the plane of the contact, the number of contacts per unit area, and the ratio of the actual contact area to the total area. The authors outline a method for determining these parameters graphically. This paper describes a method for obtaining analog voltages of surface profiles of contacting surfaces and the application of a general purpose analog computer to determine the geometric parameters of contact as a function of contact pressure. The results of applying this method are combined with the analysis of Fenech and Rohsenow. The predicted contact conductance is found to agree well with experimental data at mean contact temperatures of 100, 200, and 300 F for load pressures of 100 to 20,000 psi.

scholarly journals Study on Thermal Contact Resistance Estimation in Planar Medium

2018 ◽  
Vol 36 (1) ◽  
pp. 28-34
Author(s):  
Jingjing Wen ◽  
Leitao Li ◽  
Chengwu Liu ◽  
Bin Wu
Keyword(s):  
Heat Transfer ◽  
Contact Resistance ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Estimation Methods ◽  
Transfer Model ◽  
Calculation Error ◽  
Contact Interface ◽  
Temperature Measuring ◽  
Planar Medium

Thermal contact resistance(TCR) is one of the important parameters in heat transfer problems of engineering, and it is necessary to estimate the value of TCR effectively in many engineering fields. Considering the limitation of current estimation methods of TCR such as only focusing on one-dimensional thermal conduction, getting a single value of TCR merely, and the temperature measuring points only being placed in temperature gradient direction of mediums, boundary element method(BEM) and conjugate gradient method are combined to estimate the TCR in planar mediums. The value of TCR in relation to the position of contact interface line is estimated with this method, and the positions of temperature measuring points can be selected randomly because of the characteristic of BEM that there is no necessity to discrete the inner area and it is sufficient to discrete the boundary. The analysis of calculation examples base on heat transfer model of planar medium demonstrates that:this method can estimate the TCR effectively, but the ill-posedness is also existed in this method which is one of the inverse problems, and the calculation error of TCR is increased with the distance from temperature measuring points to contact interface, the estimation precision and stability can be improved after optimization with least square method.

scholarly journals AN INNOVATIVE METHOD OF THERMAL CONTACT HEATING AND MELTING OF HYDROCARBON MIXTURES TO OBTAIN SOFT DOSAGE FORMS

2020 ◽  
Author(s):  
Oleksandr Obodovych ◽  
◽  
Olesya Stepanova ◽  
Keyword(s):  
Heat Exchange ◽  
Thermal Contact ◽  
High Energy ◽  
Large Temperature ◽  
Hydrocarbon Mixtures ◽  
Exchange Processes ◽  
Contact Heating ◽  
Urgent Task ◽  
Wide Range ◽  
Energy Consuming

Heat exchange processes are of great importance for the implementation of technological operations in many industries, including the pharmaceutical, food and refining industries. The problem of heat transfer intensification is especially important for the creation of high-energy-efficient equipment. Heat-exchange processes of heating and melting are labor-intensive and energy-consuming, where it is necessary to transfer substances or mixtures from a solid state to a sufficiently fluid one to ensure their further transportation to the next stages of production. The peculiarity of hydrocarbon mixtures lies in their thermophysical properties: a wide range of changes in the phase transition temperature or melting point (37…100 °C), a tendency to thermal destruction and a low thermal conductivity (0.034… 0.34 W/m ∙ K). Traditionally, reactors with different mixer designs, baths with coils, electric tissue heaters, heating chambers, etc. are used at enterprises for heating and melting hydrocarbon mixtures. Mostly equipment is purchased abroad, for the purchase of which a lot of money is spent. Such methods are long and energy-intensive, there are large temperature gradients, which often leads to overheating of one part of the substance and underheating of another. In addition, the process of loading mixtures into boilers and their subsequent unloading is problematic and contaminatingly dangerous. Given all this, the development and implementation of domestic innovative technologies and equipment for the processes of heating and melting of hydrocarbon mixtures is an urgent task.

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