Sensitivity Analysis and Inverse Problems in Microscale Heat Transfer

2015 ◽  
Vol 362 ◽  
pp. 209-223 ◽  
Author(s):  
Ewa Majchrzak ◽  
Jolanta Dziatkiewicz ◽  
Łukasz Turchan
Keyword(s):  
Heat Transfer ◽  
Sensitivity Analysis ◽  
Inverse Problems ◽  
Initial Conditions ◽  
Short Pulse ◽  
Relaxation Times ◽  
Coupling Factor ◽  
Hyperbolic Model ◽  
Short Pulse Laser ◽  
Microscale Heat Transfer

In the paper the selected problems related to the modeling of microscale heat transfer are presented. In particular, thermal processes occurring in thin metal films exposed to short-pulse laser are described by two-temperature hyperbolic model supplemented by appropriate boundary and initial conditions. Sensitivity analysis of electrons and phonons temperatures with respect to the microscopic parameters is discussed and also the inverse problems connected with the identification of relaxation times and coupling factor are presented. In the final part of the paper the examples of computations are shown.

Simulation Based Study on Ultra-Short Pulse Laser Welding of Dissimilar Materials Expending Phase Lag Influence

2017 ◽  
Author(s):  
Swarup Bag ◽  
M. Ruhul Amin
Keyword(s):  
Heat Transfer ◽  
Pulse Laser ◽  
Short Pulse ◽  
Relaxation Times ◽  
Heat Transfer Analysis ◽  
Phase Lag ◽  
Short Pulse Laser ◽  
Simulation Based ◽  
Ultra Short Pulse ◽  
Ultra Short Pulse Laser

In this work, the thermal simulation of dissimilar fusion welding system is demonstrated by considering the phase lag effects in ultra-short pulse laser source. When the pulse duration is comparable with the electron relaxation time, the hyperbolic effect cannot be neglected in heat transfer analysis due to femtosecond laser. The non-Fourier effect is considered for heat transfer analysis assuming finite delay in development of temperature within the body. This delay is represented in terms of relaxation times connected to heat flux and temperature gradient. In the present work, the simulation has been proposed by developing 3D finite element based heat transfer model using dual phase lag effect. Since the experimental basis of transient temperature distribution in ultra-short pulse laser is extremely difficult or nearly impossible, the model results have been validated with literature reported results. The model has been used further for the simulation of temperature distribution in femtosecond fiber laser welding of dissimilar aluminum alloy and stainless steel. The results in terms of computed isotherm are compared with experimentally evaluated weld pool geometry for dissimilar materials from independent literature. The influence of other characteristic parameters like pulse frequency, pulse width and relaxation times are assessed for this simulation based study which will effectively reduce the costly experimental effort for differential influence of process parameters. A clear guideline of geometric shape and size of weld pool geometry and peak temperature of the welding system with reference to predictable laser parameters are the effective output of this simulation based study. It was observed that the peak temperature reached in a very short interval of time, in the order of nano-seconds. Such high heating or cooling rate impacts on the microstructural changes of the welded joint. In order to reach certain temperature, multiple pulses are required in the material processing of either very thin film or microwelding to keep the thermal shock distortion as low as possible.

Analysis of Microscale Heat Transfer and Ultrafast Thermoelasticity in a Multi-Layered Metal Film

2009 ◽  
Author(s):  
Tsung-Wen Tsai ◽  
Yung-Ming Lee ◽  
Yang-Hsu Liao
Keyword(s):  
Heat Transfer ◽  
Short Pulse ◽  
Early Stage ◽  
Thermal Response ◽  
Laser Source ◽  
Heating Process ◽  
Hot Electron ◽  
Contact Conductance ◽  
Short Pulse Laser ◽  
Ultra Short Pulse

The micro-scale heat transfer and ultrafast thermoelasticity of a gold-chromium film subjected to ultra-short pulse laser heating is investigated. To predicate the thermal response accurately, the ballistic motion and hot electron diffusion are adopted in the laser source term. The ultrafast thermoelasticity (UTE) model with the modified laser heat source is applied to solve ultrafast thermoelastic behaviors inside a two-layered thin-film and the effect of the contact conductance on the thermo-elastic fields is included in the analysis. It is found that the excessive concentration stress appears at the interface due to the contact conductance effect. Therefore, the mechanical failure or damage may occur at the interface during the very early stage of the heating process even though the thermal resistance is extremely small (as small as 10−7 m2K/W).

Selection of heat transfer model for describing short-pulse laser heating silica-based sensor

2012 ◽  
Vol 24 (2) ◽  
pp. 285-288
Author(s):  
郝向南 Hao Xiangnan ◽  
聂劲松 Nie Jinsong ◽  
李化 Li Hua ◽  
卞进田 Bian Jintian
Keyword(s):  
Heat Transfer ◽  
Pulse Laser ◽  
Laser Heating ◽  
Short Pulse ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Short Pulse Laser ◽  
Pulse Laser Heating ◽  
Selection Of

Hierarchical Modeling of Heat Transfer in Silicon-Based Electronic Devices

2010 ◽  
Vol 132 (10) ◽  
Author(s):  
Javier V. Goicochea ◽  
Marcela Madrid ◽  
Cristina Amon
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Hierarchical Model ◽  
Hierarchical Modeling ◽  
Initial Conditions ◽  
Electronic Devices ◽  
Relaxation Times ◽  
Silicon On Insulator ◽  
Boltzmann Transport ◽  
Phonon Confinement

A hierarchical model of heat transfer for the thermal analysis of electronic devices is presented. The integration of participating scales (from nanoscale to macroscales) is achieved by (i) estimating the input parameters and thermal properties to solve the Boltzmann transport equation (BTE) for phonons using molecular dynamics (MD), including phonon relaxation times, dispersion relations, group velocities, and specific heat, (ii) applying quantum corrections to the MD results to make them suitable for the solution of BTE, and (iii) numerically solving the BTE in space and time subject to different boundary and initial conditions. We apply our hierarchical model to estimate the silicon out-of-plane thermal conductivity and the thermal response of an silicon on insulator (SOI) device subject to Joule heating. We have found that relative phonon contribution to the overall conductivity changes as the dimension of the domain is reduced as a result of phonon confinement. The observed reduction in the thermal conductivity is produced by the progressive transition of modes in the diffusive regime (as in the bulk) to transitional and ballistic regimes as the film thickness is decreased. In addition, we have found that relaxation time expressions for optical phonons are important to describe the transient response of SOI devices and that the characteristic transport regimes, determined with Holland and Klemens phonon models, differ significantly.

scholarly journals Sensitivity analysis of simplified low cost converging thermal wave technique for thin bilayer solid

2014 ◽  
Vol 3 (3) ◽  
pp. 158
Author(s):  
M. Shahril Shahril Bin Husin
Keyword(s):  
Sensitivity Analysis ◽  
Thermal Wave ◽  
Short Pulse ◽  
Low Cost ◽  
Wave Model ◽  
Physical Parameters ◽  
Transient Heating ◽  
Simple Method ◽  
Short Pulse Laser ◽  
Correlated Parameters

<div><p class="ABSabstract">In this paper, the sensitivity analysis of thermo physical parameters of the semi-infinite bilayer was presented by using a simplified converging thermal wave model. This is done under the consideration that radial flow of converging thermal wave substantially dominates in the first layer and axial thermal wave, dominates in the second layer. The sensitivity of the correlated parameters due to the 5%, 10% and 100% of increment were evaluated.. The results of the calculated temperature were simulated by Mathematica software, in order to generate a sensitivity analysis and examined by graphs. From this analysis, we concluded the optimum conditions, hence to be applied in the real experiment. Our merit on this report is for introducing a simple method of optical transient heating by using low cost equipment such as camera’s flash lamp and thermocouple, which may also apply to the short pulse laser measurement. A brief theory of the present work is presented and the results obtained from the simulation are discussed.</p></div>

Comparison of Experimental and Numerical Temperature Distributions in Tissues During Short Pulse Laser Irradiation Using Focused Beam

2006 ◽  
Author(s):  
Ashim Dutta ◽  
Gopalendu Pal ◽  
Kunal Mitra ◽  
Michael S. Grace
Keyword(s):  
Heat Transfer ◽  
Numerical Modeling ◽  
Short Pulse ◽  
Experimental Measurements ◽  
Pulse Laser Irradiation ◽  
Tissue Samples ◽  
Short Pulse Laser ◽  
Temperature Distributions ◽  
Tissue Phantoms ◽  
Focused Beam

The objective of this work is to perform experimental measurements validated with numerical modeling results for analyzing the temperature distributions and heat affected zone during short pulse laser irradiation of tissues using focused beam. A Q-switched laser is used as a radiation source. A threelayered tissue phantom model of skin consisting of epidermis, dermis, and fatty tissues is first considered for model validation. Tumors are simulated with inhomogeneities embedded inside the tissue phantoms. Experiments are next conducted with freshly excised skin tissue samples from mice and finally on live anaesthetized mice to consider the bulk effect of convective heat transfer due to blood flow. Experimental measurements of axial and radial temperature distributions for all the cases are compared with numerical modeling results obtained using Pennes' bio-heat transfer equation coupled with either traditional Fourier parabolic or non-Fourier hyperbolic heat conduction formulation. Experimentally measured temperature profiles in tissue phantoms, skin tissue samples, and live anaesthetized mice are found to match extremely well with the predictions from the non-Fourier model than the Fourier formulation by considering skin as a multi-layered medium. It is also observed that focused laser beam produces desired temperature rise at the target site with lesser radial spread compared to a collimated laser beam source.

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