scholarly journals MATHEMATICAL MODELLING OF NON-STATIONARY HEAT TRANSFER IN A MULTILAYER COMPOSITE MATERIAL

2021 ◽  
Vol 51 (1) ◽  
pp. 9-14
Author(s):  
Dmitriy V. Sorokin ◽  
Alexandr L. Nikiforov
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Composite Material ◽  
Temperature Distribution ◽  
Thermal Protection ◽  
Temperature Fields ◽  
Insulating Layer ◽  
Stationary Heat ◽  
Improved Performance ◽  
Stationary Heat Transfer

The article considers the issue of designing a composite textile material based on the use of a 3D textile matrix for firefighter combat clothing with improved performance characteristics. To reduce labour and material costs for design and create an alternative to the experimental selection of the structure and composition of the material, a mathematical model of non-stationary heat transfer in the “environment – composite material – human” system is proposed. The problem of temperature distribution at any time for the outer and inner layers is presented in the form of heat transfer in a multilayer plate. The problem of temperature distribution in the heat-insulating layer of the material is presented in the form of heat transfer through a limited rod in the air. The developed mathematical model allows calculating the distribution of temperature fields in the layers of the material at different values of the effective heat flow and determine the limit parameters of its thermal protection effect.

scholarly journals Mathematical model of heat transfer in roll caliber

2019 ◽  
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Temperature Field ◽  
Temperature Distribution ◽  
Boundary Value Problem ◽  
Boundary Conditions ◽  
Heat Equation ◽  
Rolling Mill ◽  
Thermal Process ◽  
Stationary Heat

A physical model of the thermal process in the roll caliber during the rolling of the tape on a two-roll rolling mill was constructed. A mathematical model of the temperature field of a rolling hollow roll of a rolling state of a cylindrical shape rotating about its axis with constant angular velocity is proposed. The mathematical model takes into account different conditions of heat exchange of the inner and outer surfaces of the roll with the belt and its surrounding environment. The temperature field of a hollow roll of a rolling mill is considered as an initial boundary-value problem for a homogeneous non-stationary heat equation with inhomogeneous, nonlinear boundary conditions, which also depend on the angle of rotation of the roll around its axis. The equation describes the temperature field of the rolls during uncontrolled heat transfer during rolling. It significantly depends on the time and number of revolutions around its axis. With a large number of revolutions of the roll around its axis, a quasi-stationary temperature distribution occurs. Therefore, the simplified problem of determining a quasistationary temperature field, which is associated with a thermal process that is time-independent, is considered further in the work. In this case, the temperature field is described using the boundary value problem in a ring for a homogeneous stationary heat equation with inhomogeneous boundary conditions and heat transfer conditions outside the ring, which lie from the angular coordinate. After the averaging operation, the solution of this problem is reduced to solving the equivalent integral equation of Hammerstein type with a kernel in the form of the Green's function. The Mathcad computer mathematical system builds the temperature distribution of the roll surface. An algorithm for solving a inhomogeneous problem was developed and the temperature distribution of the roll was constructed.

Experimental Investigation of Non Stationary Heat Transfer Between Fluid and Solid Body

2013 ◽  
Author(s):  
Jerzy Marcinkiewicz ◽  
Jan Taler ◽  
Artur Cebula
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Solid Body ◽  
Computer Tomography ◽  
The Body ◽  
Measuring System ◽  
Temperature Fields ◽  
Measuring Error ◽  
Stationary Heat ◽  
Stationary Heat Transfer

The presented work is a result of actions taken in connection to analyses of root cause of damages (cracks and one brake) in the control rod shafts in Swedish BWR Forsmark 3. The damages were detected during the refueling outage 2008. It has been found that damages were caused by thermal fatigue. Extensive analyses of flow and temperature fields around the shaft were performed using transient CFD calculations [1, 2]. The character of the fluctuating thermal loadings on the shaft was confirmed by a limited experiment [3]. However the CFD-calculations of heat transfer between the water and the shaft have not been validated experimentally. In order to validate CFD-calculations of heat transfer between the water and the solid body the measurements of the non-stationary heat transfer are planned. The paper presents the method of determination of heat flux and temperature on the surface of the body based on temperature measurements at some discrete points beneath the surface and solving the inverse heat conduction problem (IHCP). Software was developed for performing measurements and calculations. Main parts of measurement system particularly design and manufacturing of measuring items, thermocouple installation, construction of test stand for initial testing and calibration are described. Verification of thermocouple locations was performed using computer tomography and the actual locations were introduced in to the calculation algorithm in order to improve accuracy of heat flux determination. Heat flux measuring error has been determined based on assumed random error in temperature measurement and accuracy of location verification (computer tomography). Results of initial verifying tests are presented and discussed. The measuring system is now ready for performing measurements of transient heat transfer in configurations that can occur in a reactor environment.

scholarly journals MATHEMATICAL MODELING OF HEAT TRANSMISSION THROUGH THE ENCLOSURE CONSTRUCTION

2020 ◽  
pp. 29-39
Author(s):  
A. Grazhdankin ◽  
V. Ivanchenko ◽  
A. Pis'menskiy
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Temperature Distribution ◽  
Dissimilar Materials ◽  
Building Envelope ◽  
Transfer Resistance ◽  
Space Planning ◽  
Air Temperatures ◽  
The Mathematical Model ◽  
Stationary Heat Transfer

Currently, the main direction of energy saving in mass construction is the energy efficiency of structural and space-planning solutions of buildings and structures. To evaluate the thermotechnical qualities of the enclosure, it is necessary to know the value of the heat transfer resistance and the temperature in any plane of the enclosure at given air temperatures on one and the other side of the enclosure. To understand and describe the processes of heat transfer, as well as to determine the temperature distribution inside the enclosing structures, Tabunshchikov Y.A. and Brodach M.M. derived a mathematical model of heat transfer through the enclosing structure. When considering one-dimensional heat transfer perpendicular to the wall surface at the internal borders between dissimilar materials of the building envelope, it is assumed that the temperature functions T (x) and the heat flow Q (x) are continuous. The article presents an analytical and numerical solution of a boundary value problem for stationary heat transfer through a multilayer enclosing structure, as well as a comparison of the obtained solution with the current regulatory documentation. An experimental study is conducted in the laboratory to compare the theoretical, obtained in the mathematical model of heat transfer given in the article, and the experimental temperature distribution, which shows greater convergence of the results and confirms the validity of the mathematical model.

Heat Removal and Thermal Stabilization of High-temperature Surfaces by a Dispersed Coolant Flow

Vestnik MEI ◽  
2021 ◽  
pp. 19-26
Author(s):  
Valentin S. Shteling ◽  
◽  
Vladimir V. Ilyin ◽  
Aleksandr T. Komov ◽  
Petr P. Shcherbakov ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flux Density ◽  
Flow Rate ◽  
Heat Flux Density ◽  
Coolant Flow ◽  
Transfer Coefficients ◽  
Stationary Heat ◽  
Heat Transfer Coefficients ◽  
Stationary Heat Transfer

The effectiveness of stabilizing the surface temperature by a dispersed coolant flow is experimentally studied on a bench simulating energy intensive elements of thermonuclear installations A test section in which the maximum heat flux density can be obtained when being subjected to high-frequency heating was developed, manufactured, and assembled. The test section was heated using a VCh-60AV HF generator with a frequency of not lower than 30 kHz. A hydraulic nozzle with a conical insert was used as the dispersing device. Techniques for carrying out an experiment on studying a stationary heat transfer regime and for calculating thermophysical quantities were developed. The experimental data were obtained in the stationary heat transfer regime with the following range of coolant operating parameters: water pressure equal to 0.38 MPa, water mass flow rate equal to 5.35 ml/s, and induction heating power equal to 6--19 kW. Based on the data obtained, the removed heat flux density and the heat transfer coefficients were calculated for each stationary heat transfer regime. The dependences of the heat transfer coefficient on the removed heat flux density and of the removed heat flux density on the temperature difference have been obtained. High values of heat transfer coefficients and heat flux density at a relatively low coolant flow rate were achieved in the experiments.

scholarly journals Optimizing air velocity for the underfloor forced ventilation to protect a refrigerated warehouse from frost heaving

2018 ◽  
Vol 38 (3) ◽  
pp. 321-327
Author(s):  
Jingfu Jia ◽  
Manjin Hao ◽  
Jianhua Zhao
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Natural Ventilation ◽  
Ventilation System ◽  
Three Dimensional ◽  
Temperature Fields ◽  
Frost Heave ◽  
Forced Ventilation ◽  
Air Velocity ◽  
Set Up

Forced or natural ventilation is the most common measure of frost heave protection for refrigerated warehouse floor. To optimize air velocity for the underfloor forced ventilation system of refrigerated warehouse, a steady state three-dimensional mathematical model of heat transfer is set up in this paper. The temperature fields of this system are simulated and calculated by CFD software PHOENICS under different air velocity, 1.5m/s, 2.5m/s or 3.5m/s. The results show that the optimized air velocity is 1.5m/s when the tube spacing is 1.5m.

Non-stationary heat transfer beyond diffusion spinodal of a solution

2020 ◽  
Author(s):  
S. B. Rutin ◽  
P. V. Skripov ◽  
A. A. Igolnikov
Keyword(s):  
Heat Transfer ◽  
Stationary Heat ◽  
Stationary Heat Transfer

Heat Transfer Enhancement in Corrugated Pipes

2010 ◽  
Author(s):  
Dennis A. Siginer ◽  
F. Talay Akyildiz
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Temperature Distribution ◽  
Heat Transfer Enhancement ◽  
Temperature Fields ◽  
Governing Equations ◽  
Transfer Enhancement ◽  
Exact Analytical Solutions ◽  
Velocity And Temperature Fields ◽  
Steady Laminar

The temperature distribution and heat transfer coefficient are investigated in forced convection with Newtonian fluids in pressure gradient driven hydrodynamically and thermally fully developed steady laminar flow in transversally corrugated pipes. The governing equations are solved by means of the epitrochoid conformal mapping and exact analytical solutions are derived for the velocity and temperature fields without viscous dissipation. The effect of the corrugations and the number of waves on the friction factor, the temperature distribution and the heat transfer enhancement is discussed.

Study on a New Mathematical Model for Aggregate Air Cooling or Heating

2011 ◽  
Vol 374-377 ◽  
pp. 1882-1886
Author(s):  
Li Juan Wang ◽  
Yan Feng Liu ◽  
Jia Ping Liu ◽  
Fei Lu
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Heat Transfer Coefficient ◽  
Temperature Distribution ◽  
Hydraulic Structure ◽  
Surface Heat ◽  
Air Cooling ◽  
Foundation Engineering ◽  
Heating Capacity ◽  
Surface Heat Transfer Coefficient

Before the construction of hydraulic structure, aggregate must be cooled or heated by air (we call it aggregate air cooling or heating in this paper) or other technologies to the required temperature. Previous model of aggregate air cooling or heating cannot provide the center temperature of each aggregate. So a more accurate mathematical model is developed to determine the thermal performance of aggregate, and the surface heat transfer coefficient of wet aggregate is revised. This model can predict the center temperature of an aggregate and can accurately calculate the cold down time or temperature distribution of aggregate, so that the refrigeration or heating capacity can be reasonably supplied. It’s significant for foundation engineering of hydraulic structure.

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