Anisotropic heat transfer prediction of multiscale wires using pulse laser thermal relaxation technique

2013 ◽  
Vol 555 ◽  
pp. 239-246 ◽  
Author(s):  
Jin W. Tan ◽  
Yue Cheng ◽  
Denis S.G. Yap ◽  
Feng Gong ◽  
Son T. Nguyen ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pulse Laser ◽  
Thermal Relaxation ◽  
Relaxation Technique

scholarly journals Thermal Relaxation in Titanium Nanowires: Signatures of Inelastic Electron-Boundary Scattering in Heat Transfer

2017 ◽  
Vol 189 (3-4) ◽  
pp. 204-216 ◽  
Author(s):  
Teemu Elo ◽  
Pasi Lähteenmäki ◽  
Dmitri Golubev ◽  
Alexander Savin ◽  
Konstantin Arutyunov ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Relaxation ◽  
Inelastic Electron ◽  
Boundary Scattering

Modeling and Simulation on Heat Transfer in Blood Vessels Subject to a Transient Laser Irradiation

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Xuelan Zhang ◽  
Liancun Zheng ◽  
Lin Liu ◽  
Xinxin Zhang
Keyword(s):  
Heat Transfer ◽  
Blood Vessels ◽  
Laser Irradiation ◽  
Numerical Solutions ◽  
Thermal Relaxation ◽  
Initial Time ◽  
Laser Exposure ◽  
Conduction Model ◽  
Heaviside Step Function ◽  
The Impact

Abstract This paper investigates heat transfer of blood vessels subject to transient laser irradiation, where the irradiation is extremely short times and has high power. The modified Fourier heat conduction model (Cattaneo–Christov flux) and Heaviside step function are used in describing the thermal relaxation and temperature jump characteristics in initial time. A novel auxiliary function is introduced to avoid three-level discretization and temporal–spatial mixed derivative, and the numerical solutions are obtained by Crank–Nicolson alternating direction implicit (ADI) scheme. Results indicate that the temperature distributions in blood vessels strongly depend on the blood property, the laser exposure time, the blood flowrate (Reynolds number) and the thermal relaxation parameter. The isothermal curve exhibits asymmetric characteristics due to the impact of blood flow, and the higher blood velocity leads to more asymmetric isotherm and less uniform thermal distribution. Further, the heat-flux relaxation phenomenon is also captured, and its effect on blood temperature becomes more noticeable as blood flows downstream of blood vessels.

Characterization of CeO2Ultrafine Particles Prepared Using a Thermal Relaxation Technique

1996 ◽  
Vol 25 (1) ◽  
pp. 75-76 ◽  
Author(s):  
Toshiyuki Masui ◽  
Ken-ichi Machida ◽  
Takao Sakata ◽  
Hirotaro Mori ◽  
Gin-ya Adachi
Keyword(s):  
Thermal Relaxation ◽  
Relaxation Technique

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.

Investigation on Ultrashort Pulse Laser Welding of Dissimilar Metallic Materials Expending Phase-Lag Influence

2020 ◽  
Vol 12 (5) ◽  
Author(s):  
Swarup Bag ◽  
M. Ruhul Amin
Keyword(s):  
Heat Transfer ◽  
Pulse Laser ◽  
Weld Pool ◽  
Ultrashort Pulse ◽  
Relaxation Times ◽  
Heat Transfer Analysis ◽  
Phase Lag ◽  
Ultrashort Pulse Laser ◽  
Weld Pool Geometry ◽  
Welding System

Abstract When the femtosecond laser pulse is comparable to the electron relaxation time, the hyperbolic effect cannot be neglected in heat transfer analysis. The non-Fourier effect is considered for heat transfer analysis assuming finite delay in the development of temperature within the body. This delay is represented in terms of two relaxation times connected to heat flux and temperature gradient. In the present work, a 3D finite element-based heat transfer model is developed using a dual-phase-lag effect. Since the experimental basis of transient temperature distribution in ultrashort pulse laser is extremely difficult or nearly impossible, the model results have been validated with the literature reported results. Furthermore, the simulation of dissimilar fusion welding system treated by an ultrashort pulse laser is demonstrated. The typical characteristic of thermal behavior with the application of femtosecond fiber laser on welding of dissimilar aluminum alloy and stainless steel is presented. The model results in the form of computed isotherm are compared with the literature reported weld pool geometry for dissimilar materials. The feasibility of characteristic parameters like pulse frequency, pulse width, and relaxation times are assessed in this study. A clear guideline of the geometric shape and size of weld pool geometry and the peak temperature of the welding system corresponding to predictable laser parameters is the effective output from this study. Peak temperature reached in a very short interval of time (∼ nanosecond) is analogous to a high rate of heating or cooling that affects the microstructural changes, specifically the formation of intermetallic for dissimilar welding.

ANALYTICAL SOLUTIONS OF NON-FOURIER PENNES AND CHEN–HOLMES EQUATIONS

2012 ◽  
Vol 05 (04) ◽  
pp. 1250022 ◽  
Author(s):  
WEIPING ZHU ◽  
FANGBAO TIAN ◽  
PENG RAN
Keyword(s):  
Heat Transfer ◽  
Analytical Solutions ◽  
Laplace Transformation ◽  
Solution Method ◽  
Thermal Relaxation ◽  
Blood Perfusion ◽  
Good Alternative ◽  
Tissue Temperature ◽  
Particular Solution ◽  
Insight Into

The analytical solutions of non-Fourier Pennes and Chen–Holmes equations are obtained using the Laplace transformation and particular solution method in the present paper. As an application, the effects of the thermal relaxation time τ, the blood perfusion wb, and the blood flow velocity v on the biological skin and inner tissue temperature T are studied in detail. The results obtained in this study provide a good alternative method to study the bio-heat and a biophysical insight into the understanding of the heat transfer in the biotissue.

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