Numerical Determination of the Temperature Dependent Thermophysical Properties in Solid Materials: Experimental Instrumentation

2010 ◽  
Author(s):  
Joaquin Zueco ◽  
O. Anwar Be´g
Keyword(s):  
Inverse Problem ◽  
Physical Properties ◽  
Difference Equations ◽  
Heat Conduction Problem ◽  
Temperature Measurements ◽  
Mathematical Function ◽  
Temperature Dependent ◽  
Solid Materials ◽  
Partial Difference ◽  
Thermo Physical Properties

An iterative approach is presented to determine the temperature-dependent thermo-physical properties from the temperature measurements taken at various points of the medium. Network Simulation Method (NSM) is used as the numerical tool in the form of an inverse problem to obtain a stable and exact numerical solution for simultaneously estimating thermal conductivity and specific heat. The approach provides estimations of the functions k(T) and ce(T), regardless of the waveform of those functions even without a priori information on the kind of dependence concerned. The solutions are reached by a piece-wise functions, whose number of stretches may be specified. The input data (temperature measurements) are obtained from an experimental installation has been designed and using various points of measurement in different solid materials. The sensitivity of the functional versus the slope of the line, at each step, is acceptable and the complete piece-wise solution is very close to the exact thermo-physical properties in all the cases studied. The proposed general procedure may be applied regardless of the kind of temperature dependence for k(T) and ce(T) as long as these are continuous temperature functions given by an explicit mathematical function or by a finite stretches piece-wise function. The estimations of k(T) and ce(T) are piece-wise functions with a number of stretches that may be specified to approximate the inverse solutions to the exact values as much as required. The typical functional of these problems contains the simulated measured data taken at three points of the solid. These measurements are compared in the functional with the solution of the partial inverse problem by applying NSM as the numerical technique in each iteration, in order to estimate each of the stretches that conform the whole piece-wise estimation. NSM has been successfully applied before to solve both DHCP and IHCP. Among the advantages of this method is the fact that no mathematical manipulations or convergence criteria are needed to solve the finite difference equations resulting from the discretization of the partial difference equations of the mathematical model. Both tasks are carried out by the powerful software used to solve the network model. The close agreement between the exact solutions and the estimated results shows the potential of the proposed method in finding the accurate value of the temperature-dependent thermo-physical properties in inverse heat conduction problem.

scholarly journals Reconstruction of the thermal properties in a wave-type model of bio-heat transfer

2020 ◽  
Vol 30 (12) ◽  
pp. 5143-5167
Author(s):  
Moataz Alosaimi ◽  
Daniel Lesnic ◽  
Jitse Niesen
Keyword(s):  
Heat Transfer ◽  
Physical Properties ◽  
Thermal Wave ◽  
Wave Model ◽  
Temperature Measurements ◽  
Dimensionless Parameters ◽  
Content Type ◽  
Boundary Temperature ◽  
Dimensional Parameters ◽  
Thermo Physical Properties

Purpose This study aims to at numerically retrieve five constant dimensional thermo-physical properties of a biological tissue from dimensionless boundary temperature measurements. Design/methodology/approach The thermal-wave model of bio-heat transfer is used as an appropriate model because of its realism in situations in which the heat flux is extremely high or low and imposed over a short duration of time. For the numerical discretization, an unconditionally stable finite difference scheme used as a direct solver is developed. The sensitivity coefficients of the dimensionless boundary temperature measurements with respect to five constant dimensionless parameters appearing in a non-dimensionalised version of the governing hyperbolic model are computed. The retrieval of those dimensionless parameters, from both exact and noisy measurements, is successfully achieved by using a minimization procedure based on the MATLAB optimization toolbox routine lsqnonlin. The values of the five-dimensional parameters are recovered by inverting a nonlinear system of algebraic equations connecting those parameters to the dimensionless parameters whose values have already been recovered. Findings Accurate and stable numerical solutions for the unknown thermo-physical properties of a biological tissue from dimensionless boundary temperature measurements are obtained using the proposed numerical procedure. Research limitations/implications The current investigation is limited to the retrieval of constant physical properties, but future work will investigate the reconstruction of the space-dependent blood perfusion coefficient. Practical implications As noise inherently present in practical measurements is inverted, the paper is of practical significance and models a real-world situation. Social implications The findings of the present paper are of considerable significance and interest to practitioners in the biomedical engineering and medical physics sectors. Originality/value In comparison to Alkhwaji et al. (2012), the novelty and contribution of this work are as follows: considering the more general and realistic thermal-wave model of bio-heat transfer, accounting for a relaxation time; allowing for the tissue to have a finite size; and reconstructing five thermally significant dimensional parameters.

scholarly journals Application of the RBF Method to the Estimation of Temperature on the External Surface in Laminar Pipe Flow

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Shiqin Lyu ◽  
Can Wu ◽  
Sufang Zhang
Keyword(s):  
Inverse Problem ◽  
Direct Problem ◽  
External Surface ◽  
Heat Conduction Problem ◽  
Main Idea ◽  
Inverse Heat Conduction Problem ◽  
Laminar Flows ◽  
Temperature Measurements ◽  
Control Technique ◽  
Unknown Boundary

The inverse heat conduction problem on the heat transfer characteristics of cooled/heated laminar flows through finite length thick-walled circular tubes is studied, using temperature measurements taken at several different locations within the fluid in this paper. The method of radial basis functions is coupled with the boundary control technique to estimate the unknown temperature on the external surface of the circular pipe. The main idea of the proposed method is to solve the direct problem instead of solving the inverse problem directly. The temperature data obtained from the direct problem are used to simulate the temperature measurement for the inverse problem, and during the calculation, the Tikhonov regularization and L-curve methods are employed to solve the inverse problem. Therefore, this study also considers the influence of errors in these measurements upon the precision of the estimated results as well as the influence of the locations and number of sensors used upon the accuracy of the estimated results. The results indicate that the accuracy of the estimated results is improved by taking temperature measurements in locations close to the the unknown boundary. Finally, the results confirm that the proposed method is capable of yielding accurate results even when errors in the temperature measurements are present.

scholarly journals Dynamics of Rising Bubbles in a Quiescent Slag Bath with Varying Thermo-Physical Properties

2020 ◽  
Vol 51 (6) ◽  
pp. 2843-2861
Author(s):  
D. Obiso ◽  
D. H. Schwitalla ◽  
I. Korobeinikov ◽  
B. Meyer ◽  
M. Reuter ◽  
...  
Keyword(s):  
Physical Properties ◽  
Bubble Dynamics ◽  
Fluid Dynamic ◽  
Temperature Gradients ◽  
Slag Bath ◽  
Bubble Motion ◽  
Temperature Dependent ◽  
Slag Properties ◽  
Temperature Dependent Properties ◽  
Thermo Physical Properties

AbstractThe motion of bubbles in a liquid slag bath with temperature gradients is investigated by means of 3D fluid dynamic computations. The goal of the work is to describe the dynamics of the rising bubbles, taking into account the temperature dependency of the thermo-physical properties of the slag. Attention is paid to the modeling approach used for the slag properties and how this affects the simulation of the bubble motion. In particular, the usage of constant values is compared to the usage of temperature-dependent data, taken from models available in the literature and from in-house experimental measurements. Although the present study focuses on temperature gradients, the consideration of varying thermo-physical properties is greatly relevant for the fluid dynamic modeling of reactive slag baths, since the same effect is given by heterogeneous species and solid fraction distributions. CFD is applied to evaluate the bubble dynamics in terms of the rising path, terminal bubble shape, and velocity, the gas–liquid interface area, and the appearance of break-up phenomena. It is shown that the presence of a thermal gradient strongly acts on the gas–liquid interaction when the temperature-dependent properties are considered. Furthermore, the use of literature models and experimental data produces different results, demonstrating the importance of correctly modeling the slag’s thermo-physical properties.

Multi-Parameter Estimation in Hyperthermia Problem by Using an Optimal Choice of Descent Parameters in Iterative Methods

2002 ◽  
Author(s):  
Tahar Loulou ◽  
Elaine P. Scott
Keyword(s):  
Physical Properties ◽  
Heat Conduction Problem ◽  
Numerical Procedure ◽  
Blood Perfusion ◽  
Treatment Quality ◽  
Accurate Estimation ◽  
Heating Process ◽  
Hyperthermia Treatment ◽  
Transient Heating ◽  
Thermo Physical Properties

This paper describes a numerical procedure conducted to estimate thermo-physical properties of the human tissue during hyperthermia treatment of a cancerous region. The estimation algorithm is based on the solution of an inverse heat conduction problem. The Gauss-Newton method is used to estimate simultaneously the volumetric heat capacity, the thermal conductivity, and the volumetric blood rate (blood perfusion) in the bio-heat transfer equation during a hyperthermia treatment cycle. The treatment quality of hyperthermia is analyzed by the computation of the thermal dose which is obtained from the resulting temperature field in the tissue. The importance of an accurate estimation of the thermo-physical properties of the tissue lies in that they are the most important factors for achieving a high precision heating cycle which results in an optimized treatment. The inverse analysis is based on the temperature measurements taken inside the cancerous tissue region during the transient heating process. An experimental optimization procedure is conducted to make the estimated parameters as accurate as possible. Several numerical tests were performed and show that the developed method provides an accurate estimation of thermo-physical properties in a very short practical time. As the blood perfusion is very sensitive to the temperature variation in the tissue, this estimation tool can be implemented during one cycle treatment which results in an on-line thermo-physical parameter correction while the treatment is performed.

scholarly journals PYROLYSIS MODELLING AND EXPERIMENTATION FOR THERMO-PHYSICAL PROPERTIES OF CHAR FORMED FROM ABLATIVE MATERIAL

2012 ◽  
pp. 216-220
Author(s):  
S.V. Aravind Pulickel ◽  
Mangesh. B. Chaudhari
Keyword(s):  
Inverse Problem ◽  
Computer Program ◽  
Physical Properties ◽  
Thermal Response ◽  
Test Facility ◽  
Aerodynamic Heating ◽  
Computational Results ◽  
Heat Shields ◽  
Thermo Physical Properties

Ablative materials are used in heat shields of spacecrafts re-entering the atmosphere to protect them from high aerodynamic heating. A computer program has been developed to predict the pyrolysis and thermal response in ablative materials. The computational results are verified by performing experiments conducted at the test facility in Vikram Sarabhai Space Centre. The properties and thickness of char formed are crucial to determine heat ingress. Using an inverse problem, the thermo-physical properties of char formed from the ablative material, which have not been determined earlier, are estimated. Thickness of char formed is also predicted using the program.

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