Optimal Heat Input for Estimating Luikov's Parameters in a Heat and Mass Transfer Problem

International audienceIn this article, the problem of computing an optimal heat input in Luikov's heat and mass transfer problem is detailed and analyzed. The main objective is the establishment of an optimal time-dependent heat flux profile with the goal of maximizing the temperature and moisture sensitivities of some parameters to this excitation in a drying process. Such maximization makes the estimation of the desired parameters possible, easier, and with limited uncertainty intervals. It also helps to reduce the linearity dependence between the parameters of interest and the number of temperature and moisture sensors used. The estimation of the optimal heat input is obtained with Uzawa's algorithm, while the estimation of parameters is performed with Levenberg-Marquardt's method of minimization of the ordinary least-square criterion. The six dimensionless parameters characterizing Luikov's equations are estimated successfully with this optimal heat flux profile, which also helps to reduce the number of both temperature and moisture sensors needed in the estimation procedure. By doing so, the objective of estimating simultaneously the six parameters which appear in the formulation of Luikov's physical problem is reached by using a limited transient temperature and/or moisture measurements taken anywhere in the drying medium

Optimal control of thermal damage to targetted regions in a biological material

Paper No. HT-FED2004-56426, pp. 733-736; 4 pagesASME 2004 Heat Transfer/Fluids Engineering Summer ConferenceVolume 4Conference Sponsors: Heat Transfer Division and Fluids Engineering DivisionISBN: 0-7918-4693-8 | eISBN: 0-7918-3740-8International audienceA numerical technique with potential applications in hyperthermia treatment planning is presented. The treatment is simulated using a 2D transient computational model of the Pennes bioheat equation within an optimization algorithm. The algorithm recovers the heating protocol which will lead to a desired damage field. The relationship between temperature, time and thermal damage is expressed as a first order rate process using the Arrhenius equation. The objective function of the control problem is based on this thermal damage model. The adjoint method in conjunction with the conjugate gradient algorithm is used to minimize the objective function. The results from a numerical simulation show good agreement between the optimal damage field and the damage field recovered by the algorithm. A comparison between the recovered damage field and the commonly used thermal dose is also made

Numerical and Experimental Investigation on Single-Point Thermal Contact Resistance

© 2021 Springer Nature Singapore Pte Ltd. This is the accepted manuscript version of an paper/conference proceeding which has been published in final form https://doi.org/10.1007/978-981-33-4765-6_75In the engineering applications, the thermal contact resistance has an important effect of heat transfer design and operation of systems and devices. For general contact heat transfer, as long as the geometry, mechanics and boundary conditions are known, the steady thermal contact resistance of the interface will be “unique,” which is independent of theoretical prediction and experimental measurement method

Crystal structures and characterization of two divalent metal selenates templated by dabco, (C6H14N2)[MII(H2O)6](SeO4)2 (MII: NiII, ZnII)

International audienceTwo new organic-inorganic hybrid materials have been synthesized and crystallographically characterized. Both compounds, (C6H14N2)[Ni(H2O)6](SeO4)2 (I) and (C6H14N2)[Zn(H2O)6](SeO4)2 (II), crystallize isotypically in the monoclinic system, space group P21/c, with the following unit cell parameters: a = 12.4045(3), b = 11.9360(3), c = 12.8366(3) Å, β = 108.518(2)°, V = 1802.18(8) Å3, Z = 4 for compound (I) and a = 12.7839(2), b = 11.9153(4), c = 12.3814(2) Å, β = 108.264(5)°, V = 1790.97(7) Å3, Z = 4 for the zinc related phase. Their supramolecular structure consists of metallic cation octahedrally coordinated by six water molecules [MII(H2O)6]2+, selenate anions (SeO4)2- and dabcodiium cation (C6H14N2)2+ linked together via two types of hydrogen bonds, Ow-H...O and N-H...O only. The thermal decomposition of these supramolecular compounds takes place in several steps leading to the formation of metal oxide. The magnetic measurements show that the nickel based compound is predominantly paramagnetic with weak antiferromagnetic interactions at low temperature

Etude de l'influence des conditions interfaciales sur le développement du noyau lors du soudage par résistance par point

National audienceSee http://hal.archives-ouvertes.fr/docs/00/59/29/59/ANNEX/r_1280325L.pd

Effect of water based nanofluids on laminar convective heat transfer in developing region of rectangular channel

Researches involving mixing very little amount of nano-sized solid additives to base fluid have gained popular interest to develop enhanced convective heat transfer techniques. The dispersion of solid particles in such nanofluids changes the thermo physical properties of the working fluid such as viscosity, thermal conductivity, density and specific heat. Therefore, nanofluids have enhancement potential in heat transfer performance compared to normal working fluids. Additionally, most of the researches regarding heat transfer enhancement by using nanofluids considered circular tube as the geometry conducted on developed region. However, in many industry or heat generated equipment, rectangular channels are generally used as a flow path for fluid flowing to conduct heat transfer application. Therefore, the analysis of heat transfer through the entire section of channel (both developing and developed region) is important to understand flow behavior along with heat transfer performance of the entire section for industrial operation. In this study, convective heat transfer of laminar nanofluids in developing region of a rectangular channel was numerically investigated using finite volume method and single-phase approach with ANSYS Fluent software. Four nanoparticles (Al2O3, CuO, SiC and TiO2) with different volume fraction (1% - 5%) were used to mix with water to produce water based nanofluids. The heat transfer was analysed for a constant Reynolds numbers 700 with a constant heat flux 500 W/m2 applied on the channel wall. Results demonstrated 2% to 13.38% enhancement in heat transfer coefficient with the presence of 1 to 5% nanoparticles concentration, respectively, in comparison to pure water. Meanwhile, results in terms of Nusselt number showed an increase of 1.5% to 13.36% as compared to pure water for the same range of nanoparticles concentration, respectively. From these results, it can be deduced that higher nanoparticles volume fraction results in higher heat transfer coefficient and Nusselt number. Moreover, CuO-water nanofluid provides the highest enhancement in terms of both heat transfer coefficient and Nusselt number while Al2O3-water nanofluid provides lowest enhancement in terms of both heat transfer coefficient and Nusselt number among all nanofluids considered in this study. From this study, it can be concluded that water-based nanofluids provide enhancement of heat transfer coefficient and Nusselt number for laminar developing region of a rectangular channel

Combined Parameter and Function Estimation With Applications to Thermal Conductivity and Surface Heat Flux

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comparative study of Heat Flux and Temperature Based Objective Functional to Solve Inverse Heat Conduction Problems

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An inverse heat conduction problem with heat flux measurements

International audienceUsing heat flux measurements as additional information to solve inverse heat conduction problems was and is still rarely employed. Lot of disadvantages linked to heat flux measurement specificities (local disturbance, intrusive measurement, lack of knowledge and proficiency, etc.) make people prefer temperature measurements which are well documented and very widespread. Solving inverse heat conduction problems with heat flux measurements is quite different than the one which uses temperatures and need to be investigated deeply. In this work, this problem is approached through the solution of a bioengineering problem consisting in the development of a non‐invasive blood perfusion probe. The effort here is focused on the development of a methodology for the estimation of time‐dependent blood perfusion from heat flux measurements. The physical probe incorporates a thin heat flux sensor, which is placed in contact with the tissue region where the perfusion is to be measured. The sensor records the heat flux due to an imposed thermal event, which is achieved by air flow. A one‐dimensional mathematical model is used to simulate the thermal event occurring at the contact region holding between the probe and the tissue. A combined parameter and function estimation procedure is developed to estimate simultaneously time‐dependent blood perfusion and thermal contact conductance between the probe and the tissue. The robustness of the method was demonstrated through several test cases using simulated data. The presented examples include various functional changes in the time evolution of blood perfusion. Results from this study have shown the feasibility of solving inverse problems with heat flux measurements and the two unknowns are estimated with no a priori information about their functional forms

comparative study of Heat Flux and Temperature Based Objective Functional to Solve Inverse Heat Conduction Problems

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