scholarly journals Heat Transfer with Absorption in Anisotropic Thermal Protection of High-Temperature Products

2019 ◽  
pp. 35-49
Author(s):  
V.F. Formalev ◽  
S.A. Kolesnik ◽  
B.A. Garibyan
Keyword(s):  
Heat Transfer ◽  
Thermal Protection ◽  
Phenol Formaldehyde ◽  
The Body ◽  
Temperature Fields ◽  
Chemical Transformations ◽  
Heat Flows ◽  
Plate Heating ◽  
Heat Shielding ◽  
Physical And Chemical

The purpose of the research was to study the non-stationary heat transfer in anisotropic thermal protection under the action of unsteady heat flows distributed along the body, when there are thermal energy sinks inside the body, the energy being proportional to temperature, due to endothermic physical and chemical transformations. Thermal protection is made of anisotropic material, such as phenol-formaldehyde fiberglass, asboplastics, carbon-carbon plastics, etc. A new analytical solution has been obtained for the problem of plate heating under the action of unsteady heat flows distributed along the body. Using this solution, we studied the temperature fields when the components and orientation angles of the main axes of the thermal conductivity tensors of anisotropic heat-shielding materials were changed. Findings of research show that with increasing time, the temperature field inside the plate is localized and does not extend further than the limiting isotherm.

Computational Study on Radiative Aerothermodynamics of a Reentry Space Vehicle

2021 ◽  
Author(s):  
Qi Li ◽  
Sijun Zhang
Keyword(s):  
Heat Transfer ◽  
Thermal Protection ◽  
Computational Study ◽  
Space Vehicle ◽  
The Body ◽  
Stagnation Region ◽  
Convective Flux ◽  
Transit Times ◽  
Key Issues ◽  
Nonequilibrium Flows

Abstract Under hypersonic flight conditions, a vehicle travelling through the atmosphere could excite the air that flows around the body to very high temperatures as the kinetic energy of the vehicle is dissipated to the gas. Depending on the flight velocity, various chemical reactions will be produced behind a shock wave for stagnation region. These reactions greatly change the properties of air and cause considerable deviation from those of a thermally and calorically perfect gas. A vehicle flying through the higher altitude of the atmosphere at high velocities may also experience thermal non-equilibrium since the lower density reduces the collision frequency and the high velocity results in smaller transit times for the air molecules. Under such extremely thermal circumstances, the heat transfer by convection and radiation around a vehicle has been one of key issues for thermal protection system (TPS). In this paper, the computational aerothermodynamics with fully coupled radiative heat transfer is developed. To validate the proposed approach, it is employed to simulate the thermal and chemical nonequilibrium flows over Stardust. The computed results on the reentry space vehicle reveal both of convective flux and radiative flux are in good agreements with other predicted results.

scholarly journals Transformation Thermodynamics with Arbitrarily Shaped Non-Conformal Objects and Coatings

2018 ◽  
Vol 186 ◽  
pp. 01007
Author(s):  
Qingxiang Ji ◽  
Guodong Fang ◽  
Jun Liang
Keyword(s):  
Thermal Protection ◽  
Small Region ◽  
Heat Fluxes ◽  
Temperature Fields ◽  
Heat Flows ◽  
Thermal Protection Systems ◽  
Thermal Fields ◽  
Design Flexibility ◽  
Protection Systems ◽  
Concentrate Heat

In this paper we apply transformation optics theory to thermodynamics and design thermal cloaks and concentrators with arbitrarily shaped non-conformal objects and coatings. Expressions of the required material parameters are derived analytically and then validated by numerical simulations. We apply this method to design a thermal cloak which can guide the heat flow around the inner domain without perturbation to external thermal fields. In this way, the object inside the inner domain is protected from the invasion of external heat fluxes. In contrast, a concentrator is designed to concentrate heat flows into a small region without disturbing outside temperature fields, which can considerably enhance the heat density in the designed domain. The proposed method extends the design flexibility in manipulating heat flux and will find wide applications in thermal protection systems, solar cells and so on.

Transformation "Insulator-Conductor" after Laser Irradiation of the Polymer Films

2011 ◽  
Vol 496 ◽  
pp. 50-54
Author(s):  
Jimsher N. Aneli ◽  
Elena F. Semiletova ◽  
Nana V. Bakradze ◽  
Teimuraz N. Dumbadze
Keyword(s):  
Laser Irradiation ◽  
Phenol Formaldehyde ◽  
High Vacuum ◽  
Polymer Materials ◽  
Chemical Transformations ◽  
Chemical Structures ◽  
Irradiation Energy ◽  
Electrical Conducting ◽  
Physical And Chemical ◽  
Paramagnetic Properties

Abstract: Formation of electrical conducting channels with paramagnetic properties on the surface of three type polymer plates (phenol-formaldehyde and epoxy resins, polyacrylonitrile) under influence of CO2 laser irradiation at the presence of air have been studied. It is shown that the magnitude of surface resistance of the investigated polymers depends on polymer type and irradiation energy. The appearance of electrical conducting regions in the polymer materials is due to laser-chemical transformations of macromolecular physical and chemical structures near the polymer plate surfaces, leading to formation of double conjugated bonds. These structures are characterized also with paramagnetic properties- by method of ESR the free radicals are discovered in the transformed regions of polymers. The obtained results practically are analogous to ones obtained in such polymers after thermal treatment at high temperatures. However there are some advantages: in the latter case for obtaining of conducting materials on the base of dielectric polymers it is necessary to use a high vacuum. Besides of such method does not allow the formation of conducting channels with desired square and configuration on the surface of polymer plates in very short time (about several seconds) at present of air.

On Demand Thermal Protection (ODTP): A New Approach for Designing Garments Exposed to Flash Flame Incidents

2012 ◽  
Author(s):  
Eduardo Mendoza ◽  
Jean-pierre Cooper ◽  
John W. Evangelista ◽  
Margaret Auerbach ◽  
Özer Arnas
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Heat Equation ◽  
Thermal Protection ◽  
Experimental Testing ◽  
Sudden Change ◽  
Muscle Layer ◽  
The Body ◽  
On Demand ◽  
Combined Convection

Soldiers, first responders and other high risk occupations such as power line technicians are routinely exposed to dangerous situations where severe burn injuries are possible. Standard flame resistant (FR) fabrics provide minimal burn protection when exposed to a flash flame incident. As a result, improvement in thermal protection is desperately needed and remains an ongoing subject of research and development. A simplified one dimensional physical model composed of a muscle layer, skin/fat layer, air gap(s) and fabric layer(s) is used to model heat transfer entering the body covered by a garment that is exposed to a flash flame. Heat transfer within the skin and muscle layers is modeled by combined conduction, metabolic heat generation and blood perfusion by a recently developed modification to the heat equation termed the bio-heat equation. Boundary conditions include a fixed temperature (core body temperature) at the inside of the muscle layer and combined convection and radiation from the flame on the outside of the fabric. The heat equation is solved by discretizing the domain in one dimension and using a finite volume approach to derive the finite difference equations. This model is an initial step to be used to provide an assessment of common FR garments with respect to both comfort in ambient conditions and protection during a flash flame. It also provides for parametric analysis to determine ideal thermo-physical properties, fabric thicknesses and layering for better protection during flash flame incidents. Estimates for time to burn injury from the numerical model is presented with experimental results using live mannequin flame tests (ASTMF-1930), standard vertical flame tests (ISO-17492) and a non-standard flame test with combined convection and radiation heat fluxes up to 85 kW/m2. The main effort of this study revolves around an initial working design for a dynamic garment termed On Demand Thermal Protection (ODTP). The primary focus of the design is the development of a thermistor circuit embedded in a protective garment to act as an electric sensor for rapidly deploying the necessary thermal protection that is needed as predicted by the numerical model instantaneously in the event of a flash flame incident. An initial prototype is being developed with a focus on designing the thermistor circuit to mechanically actuate protective components in a flash-flame environment. Concepts include rapidly releasing a pressurized flame retardant fluid through vinyl tubing sewn into a garment and deploying a protective barrier around the face and neck when the thermistor circuit detects a sudden change in heat transfer. A summary of the prototype along with experimental testing to date compared to the theoretical predictions from the model described above is presented.

A Procedure to Evaluate the Thermal Response of a Multilayered Thermal Protection System Subjected to Aerodynamic Heating

2009 ◽  
Author(s):  
Michele Ferraiuolo ◽  
Oronzio Manca ◽  
Aniello Riccio
Keyword(s):  
Heat Transfer ◽  
Thermal Protection ◽  
Outer Space ◽  
Thermal Response ◽  
Temperature Limit ◽  
The Body ◽  
Heat Radiation ◽  
Aerodynamic Heating ◽  
Internal Temperature ◽  
Design Activities

Next generation reusable re-entry vehicles must be capable of sustaining consistent repeated aero-thermal loads without damage or deterioration. This means that such structures must tolerate the high temperatures engendered by aero-thermal re-entry fluxes due to the establishment of a hypersonic regime over the body. Thermal Protection Systems (TPS) are used to maintain a reusable launch vehicle’s structural temperature within acceptable limits during re-entry flights; that is, internal temperature should not overcome the temperature limit use of the internal structure. TPS are usually composed by several layers made of different materials. Heat transfer through a multilayer insulation during atmospheric re-entry involves combined modes of heat transfer: heat conduction through the solid, heat radiation to the outer space etc. In the frame of TPS design activities a procedure based on one dimensional analytical solutions of transient nonlinear analyses has been developed in order to estimate the temperature variation with time and space of a multilayered body subjected to aerodynamic heating inside a radiating space. Since internal temperature values of TPSs of re-entry vehicles cannot exceed certain values, that procedure allows to quickly evaluate those temperature values and to preliminary size layer thicknesses before preparing and performing Finite Element analyses.

Heat Transfer in Friction Stir Welding—Experimental and Numerical Studies

2003 ◽  
Vol 125 (1) ◽  
pp. 138-145 ◽  
Author(s):  
Yuh J. Chao ◽  
X. Qi ◽  
W. Tang
Keyword(s):  
Heat Transfer ◽  
Friction Stir Welding ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Friction Stir ◽  
Heat Flows ◽  
Numerical Studies ◽  
Weld Residual Stress ◽  
Joining Process

In the friction stir welding (FSW) process, heat is generated by friction between the tool and the workpiece. This heat flows into the workpiece as well as the tool. The amount of heat conducted into the workpiece determines the quality of the weld, residual stress and distortion of the workpiece. The amount of the heat that flows to the tool dictates the life of the tool and the capability of the tool for the joining process. In this paper, we formulate the heat transfer of the FSW process into two boundary value problems (BVP)—a steady state BVP for the tool and a transient BVP for the workpiece. To quantify the physical values of the process the temperatures in the workpiece and the tool are measured during FSW. Using the measured transient temperature fields finite element numerical analyses were performed to determine the heat flux generated from the friction to the workpiece and the tool. Detailed temperature distributions in the workpiece and the tool are presented. Discussions relative to the FSW process are then given. In particular, the results show that (1) the majority of the heat generated from the friction, i.e., about 95%, is transferred into the workpiece and only 5% flows into the tool and (2) the fraction of the rate of plastic work dissipated as heat is about 80%.

scholarly journals Thermal Modernization of the Panel Buildings External Walls

2018 ◽  
Vol 7 (3.2) ◽  
pp. 116
Author(s):  
Olena Filonenko ◽  
Oleg Yurin ◽  
Olga Kodak
Keyword(s):  
Heat Transfer ◽  
Thermal Protection ◽  
Residential Buildings ◽  
Outer Wall ◽  
Temperature Fields ◽  
Heat Conducting ◽  
Protection Level ◽  
Protective Properties ◽  
Wall Panels ◽  
Before And After

The thermal protection level of the first mass series panel buildings (series 111-94) is the lowest among residential buildings in Poltava. The problems of these buildings’ thermal modernization, is consideration of heat-conducting inclusions effect on the reduced resistance to heat transfer. In the studies such heat-conducting inclusions as the panel joints’ design, the window slope and the external wall geometry (the external corner) were taken into account. Studies were performed for the four pattern sections of the outer wall. Panels of two thickness variants with two joint designs were under consideration.To analyze the thermal protection level, the results of the two-dimensional temperature fields’ calculations were used. The analysis of the wall panels’ thermal protection level before the thermal modernization was performed. The magnitude of the heat conducting inclusions effect on reduced resistance of the walling to the heat transfer before and after the thermal modernization is determined. Possible ways of improving the wall panels’ heat-protective properties to the level of the standards in Ukraine are considered. The optimal variant of insulation for each pattern was chosen.  

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.

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 Investigation of the boundary layer zone with an aerodynamic flow around an axisymmetric spindle-shaped body for solving conjugate problems of heat and mass transfer

2021 ◽  
Vol 2131 (2) ◽  
pp. 022028
Author(s):  
T Novoselova ◽  
L Tolmacheva ◽  
A Palii ◽  
J Akopdjanyan
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Conjugate Heat Transfer ◽  
Transfer Problem ◽  
Surface Region ◽  
The Body ◽  
Temperature Fields ◽  
Similarity Coefficients ◽  
Near Surface ◽  
Shaped Body

Abstract The article discusses the possibility of calculating the thickness of the boundary layer when flowing around an axisymmetric spindle-shaped body without using empirical similarity coefficients. For this, the use of physical analogy of processes is proposed. The necessary flow conditions are described. The two-dimensional Laplace equation is solved for the near-surface region of the laminar flow around the body, obtained by rotating a curve of a given shape. When solving the problems of conjugate heat transfer, the regularities of the interaction of the flow with the body surface are taken into account, which, as a result, is reduced to the joint solution of the boundary layer equations describing the flow field and the heat conduction equations describing the propagation of temperature fields inside and outside the body. In view of the complexity or impossibility of the analytical solution of such problems, it is customary to resort to numerical methods for solving these equations. Even the numerical solution of the conjugate heat transfer problem is associated with a huge number of calculations, the availability of computing power and significant time costs. Therefore, it is customary to solve such problems in a quasi-stationary approximation, which imposes certain restrictions on the scope of application

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