Numerical solutions for general inverse heat conduction problem

A family of numerical methods for determining the space-and time-variable heat transfer coefficient, based on experimentally acquired interior temperature-time data, is presented. Newton-type methods are utilized to compute simultaneously the unknown heat transfer coefficient components. To reduce the influence of random errors in the measurement data on the estimated heat transfer coefficients, the noisy data are smoothed using least squares approximation by cubic splines. Three test examples using experimental and random simulated data are used to illustrate the computation efficiency and generality of the present methods.     

Whole time domain solution of inverse heat conduction problem in multi-layer media

The unknown surface conditions in composite media is estimated by minimizing the nonlinear least squares error between the computed and measured temperatures over the whole time domain. This approach shown to be stable, efficient and accurate. The unknown surface conditions are assumed to have an abrupt change at unknown time. A sensitivity analysis is conducted to learn more insight into the nature of difficulties that can be encountered in the estimation of the parameters associated with the inverse problem. The stability and accuracy of the method is demonstrated by several numerical examples which provide very strict test conditions. Received on 7 March 1997     

An exact mathematical solution for entrance-region laminar heat transfer with axial conduction

Summary A relatively simple mathematical scheme is proposed by which the entrance-region temperature solution for laminar flow heat transfer with axial conduction can be rigorously obtained.For Poiseuille pipe flow (parabolic velocity profile) with uniform wall heat flux, the accurate first twelve eigenvalues, eigenfunctions, and the coefficients of the series expansion which are required in the temperature solution have been determined for Peclet numbers of 5, 10, 20, 30, 50, and 100. In addition, asymptotic expressions for the eigenvalues and the eigenfunction,R _n (1), are derived. It is possible to use the asymptotic equation to predict, with satisfactory accuracy, even the first few eigenvalues for all the Peclet numbers considered.By employing the computed eigenvalues and the relevant constants, the effect of axial conduction on the entrance-region temperature profile and local Nusselt numbers has been examined and reported.This work was performed under the auspices of the U.S. Atomic Energy Commission.     

Analytical solution of the overdetermined inverse heat conduction problem with an application to monitoring thermal stresses

The paper presents a technique for determining the transient temperature distribution, when input data as thermocouple responses are known at several interior locations. If the temperature field is known, then the thermal stresses can be calculated. The problem is overdetermined and is solved using a least squares method that minimizes the error between the computed and measured thermocouple temperatures. The present method incorporates the advantages of simplicity and accuracy of analytical solutions. Several numerical examples and measurements are presented as an indication of the accuracy of the presented method. Received on 10 January 1997     

Determination of nonuniform heat flux density on boundary in inverse heat conduction problem

This paper develops reducing deviation method to solve inverse heat conduction problem with nonuniform heat flux density on boundary. When the thermocouple is placed a bit far from the boundary, there is no problem on non-convergence in this method. A calculation example is given.     

PRECISE INTEGRAL ALGORITHM BASED SOLUTION FOR TRANSIENT INVERSE HEAT CONDUCTION PROBLEMS WITH MULTI-VARIABLES

IntroductionIHCPs (InverseHeatConductionProblems)arecloselyassociatedwithmanyengineeringaspects,andwelldocumentedintheliteratures,coveringtheidentificationsofthermalparameters[1,2 ],boundaryshapes[3],boundaryconditions[4 ]andsource_relatedterms[5 ,6 ]etc .Howeveritseemsthatonlylittleworkisdirectlyconcernedwithmulti_variablesidentificationsbyauthors’knowledge.Tsengetal.presentedanapproachtodeterminingtwokindsofvariables[7],butonlygavefewnumericalexamplestodeterminethemsimultaneously .Thesol…     

Optimization of heat transfer through finned dissipators cooled by laminar flow

In the present work, the problem of optimizing the shape and the spacing of the fins of a thermal dissipator cooled by a fluid in laminar flow is studied. For a particular finned conduit, the velocity and temperature distributions on the transversal section are determined with the help of a finite element model and a global heat transfer coefficient is calculated. A polynomial lateral profile is proposed for the fins and the geometry is optimized in order to make the heat transfer coefficient as high as possible with the smallest dimensions or the lowest hydraulic resistance to the flow. The optimum fin profile and spacing, obtained by means of a genetic algorithm, are finally shown for different situations. Increases of 45% are obtained in the heat transfer coefficient referring to the maximum values which can be obtained with rectangular fin profiles.     

A boundary identification method for an inverse heat conduction problem with an application in ironmaking

A boundary identification problem in inverse heat conduction is studied, based on data from internal measurement of temperature and heat flux. Formulated as a sideways heat conduction equation, a spatial continuation technique is applied to extend the solution to a known boundary condition at the desired boundary position. Recording the positions traversed in the continuation for each time instant yields the boundary position trajectory and hence the solution of the identification problem. A prospective application of the method can be found in the ironmaking blast furnace, where it is desired to monitor the thickness of the accreted refractory wall based on measurement of its internal state. Simulations featuring noisy measurement data demonstrate the feasibility of the identification method for blast furnace wall thickness estimation.     

Formulation of Gyarmati's principle for heat conduction equation

Gyarmati's principle is formulated in various pictures for the heat conduction phenomenon in solid. Since the heat current density and the internal energy function can be given in three different pictures for heat conduction phenomena, we get the nine forms of the principle from which the heat conduction equation can be derived. This formulation has been shown using the generalized picture. In the subsequent section the principle is formulated in proper picture from which three proper pictures namely Fourier, entropy and energy follow.

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Formulierung des Prinzips von Gyarmati für Wärmeleitprobleme

Zusammenfassung Das Prinzip von Gyarmati wird in verschiedenen Arten für Wärmeleitphänomene formuliert. Da die Wärmestromdichte und die innere Energie in drei verschiedenen Arten für Wärmeleitphänomene angegeben werden können, erhalten wir die neun Formen des Prinzips, von denen die Wärmeleitgleichung abgeleitet werden kann. In dieser Formulierung wird ein verallgemeinertes -Bild verwendet. Im folgenden Teil wird das Prinzip in einem geeigneten -Bild formuliert, von dem drei geeignete Bilder folgen, nämlich das Fourier-, das Entropie- und das Energie-Bild.

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Nomenclature rate of entropy production - dissipation potential function of thermodynamic forces only - dissipation potential function of fluxes only - v volume of the system - x _i thermodynamic forces - J _i thermodynamic currents - f number of irreversible processes taking place in the system - L_iK phenomenological coefficients representing conductivity of the material - R_iK phenomenological coefficients representing resistances - density of the material - a specific value of the extensive transport quantity - _i state parameters, the gradients of which give rise to the thermodynamic forces - _i source density of a_i - s specific entropy - T absolute temperature - J _q heat current density vector - heat conductivity coefficient - L_qq phenomenological coefficient corresponding to heat conductivity coefficient - x _q thermal dissipative force - _q entropy production due to heat transfer - u specific internal energy - L phenomenological coefficient in picture - c_V specific heat at constant volume     

Solution of the laminar duct flow problem by a boundary integral equation method

Summary A boundary integral equation method is proposed for approximate numerical and exact analytical solutions to fully developed incompressible laminar flow in straight ducts of multiply or simply connected cross-section. It is based on a direct reduction of the problem to the solution of a singular integral equation for the vorticity field in the cross section of the duct. For the numerical solution of the singular integral equation, a simple discretization of it along the cross-section boundary is used. It leads to satisfactory rapid convergency and to accurate results. The concept of hydrodynamic moment of inertia is introduced in order to easily calculate the flow rate, the main velocity, and the fRe-factor. As an example, the exact analytical and, comparatively, the approximate numerical solution of the problem of a circular pipe with two circular rods are presented. In the literature, this is the first non-trivial exact analytical solution of the problem for triply connected cross section domains. The solution to the Saint-Venant torsion problem, as a special case of the laminar duct-flow problem, is herein entirely incorporated.     

A note on heat transfer in laminar flow through a gap

Summary The problem of heat transfer in laminar flow through a gap between two semi-infinite parallel plates at constant temperature was recently studied by Agrawal¹⁾. He solved this problem with the use of infinite Fourier sine series and derived an expression for the local temperature profile and the local Nusselt number as a function of the distance along the gap. A detailed solution for Péclèt number Pe=1 is given. Far enough from the entrance of the gap the local temperature profile of the fluid is almost independent of it's initial temperature. In this paper this limit temperature profile is expressed with the confluent hypergeometric function and the corresponding Nusselt number as a function of Pe is calculated.     

A semi-numerical method for solving inverse heat conduction problems

A semi-numerical method is presented for solving the inverse heat conduction problems in homogeneous and composite bodies. The presented solution does not require both the initial temperature distribution in the body and the whole temperature-time history at the temperature sensor locations. Sample calculations confirm that this approach produces stable and accurate results for both exact and noisy data. The extension of the method presented to two or three dimensions is straightforward.     

The conduction of fluctuating heat flow

Summary It has previously been known that, for calculation of temperatures and heat flows that vary sinusoidally with time, homogeneous slabs or hollow cylinders may be considered as passive four-poles. Extension of this idea is now shown to be possible for non-infinite slabs and cylinders and for situations wherein the temperature or heat flow over the whole surface is not independent of the position in the surface.     

A space marching method for multidimensional transient inverse heat conduction problems

A new method for the solution of multidimensional heat conduction problems is formulated. The developed space marching method allows to determine quickly and exactly unsteady temperature distributions in the construction elements of irregular geometry. The method is especially appropriate for determining transient temperature distribution in thick-wall pressure components based on temperature measurements at the outer surface. Two examples are included to demonstrate the capabilities of the new approach. Received on 28 October 1998     

Relaxation equation of heat conduction and generation — an analytical solution by Laplace transforms method

Heat and Mass Transfer - The relaxation equation of heat conduction and generation permits the relaxation of heat flux (a finite speed of heat propagation) as well as the relaxation of heat source...     

Finite element method solution of simultaneous two-dimensional heat and mass transfer in laminar film flow

A finite element solution is given for the coupled heat and mass transfer taking place when a vapour with considerable heat of absorption is absorbed into a laminar film flow. Convection and diffusion parallel and perpendicular to the direction of flow are taken into account. Temperature and mass fraction profiles across the film are given as well as results in film flow direction for several values of the Peclet number. Comparison with a solution based on one-dimensional flow and diffusion perpendicular to the flow, shows that deviations from this case by our two-dimensional solution increase for decreasing Peclet number.