Development Of Temperature Distribution Research Articles

Modeling of Melt Flow and Heat Transfer in Stationary Gas Tungsten Arc Welding with Vertical and Tilted Torches.

A 3D numerical simulation was conducted to study the transient development of temperature distribution in stationary gas tungsten arc welding with filler wire. Heat transfer to the filler wire and the workpiece was investigated with vertical (90°) and titled (70°) torches. Heat flux, current flux, and gas drag force were calculated from the steady-state simulation of the arc. The temperature in the filler wire was determined at three different time intervals: 0.12 s, 0.24 s, and 0.36 s. The filler wire was assumed not to deform during this short time, and was therefore simulated as solid. The temperature in the workpiece was calculated at the same intervals using heat flux, current flux, gas drag force, Marangoni convection, and buoyancy. It should be noted that heat transfer to the filler wire was faster with the titled torch compared to the vertical torch. Heat flux to the workpiece was asymmetrical with both the vertical and tilted torches when the filler wire was fully inserted into the arc. It was found that the overall trends of temperature contours for both the arc and the workpiece were in good agreement. It was also observed that more heat was transferred to the filler wire with the 70° torch compared with the 90° torch. The melted volume of the filler wire (volume above 1750 °K) was 12 mm3 with the 70° torch, compared to 9.2 mm3 with the 90° torch.

Development of Temperature Distribution and Light Propagation Model in Biological Tissue Irradiated by 980 nm Laser Diode and Using COMSOL Simulation.

Introduction: The purpose of this project is to develop a mathematical model to investigate light distribution and study effective parameters such as laser power and irradiated time to get the optimal laser dosage to control hyperthermia. This study is expected to have a positive impact and a better simulation on laser treatment planning of biological tissues. Moreover, it may enable us to replace animal tests with the results of a COMSOL predictive model. Methods: We used in this work COMSOL5 model to simulate the light diffusion and bio-heat equation of the mouse tissue when irradiated by 980 nm laser diode and the effect of different parameters (laser power, and irradiated time) on the surrounding tissue of the tumor treatment in order to prevent damage from excess heat Results: The model was applied to study light propagation and several parameters (laser power, irradiated time) and their impact on light-heat distribution within the tumor in the mouse back tissue The best result is at laser power 0.5 W and time irradiation 0.5 seconds in order to get the maximum temperature hyperthermia at 52°C. Conclusion: The goal of this study is to simulate a mouse model to control excess heating of tissue and reduce the number of animals in experimental research to get the best laser parameters that was safe for use in living animals and in human subjects.

Thermal radiation effects of a high‐temperature developing laminar flow in a tube

AbstractThe thermal radiation effects of a high‐temperature developing laminar flow in a tube are investigated numerically. The two‐dimensional steady flow and heat transfer are considered for an absorbing‐emitting gray medium, whose density is dependent on the temperature. The governing equations of the coupled process are simultaneously solved by the discrete ordinate method combined with the control volume method. For a moderate optical thickness, the velocity distribution, the temperature distribution, and the radial heat flux distribution in the medium as well as the heat flux distribution on the tube wall are presented and discussed. The results show that the thermal radiation effects of a high‐temperature medium are significant under a moderate optical thickness. The flow and convective heat transfer are weakened, and the development of temperature distribution is accelerated noticeably. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(5): 299–306, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20018

A Model of Heat and Mass Transfer in a Porous Cometary Nucleus Based on a Kinetic Treatment of Mass Flow

The main aspect of this paper is to provide a synthesis between two major lines of development in the understanding of mass and heat transfer in a volatile porous medium. The first one is a macroscopic approach, where the medium is considered as a continuum, and heat and mass transfer equations are solved under appropriate boundary conditions for temperature and gas pressure (G. Steiner and N. I. Kömle 1991, Planet. Space Sci. 39, 507–513; Y. Mekler et al. 1990, Astrophys. J. 356, 682–686; S. J. Espinasse et al. 1991, Icarus 92, 350–365), while the second one is a kinetic model, calculating gas flow in tubes under the assumption of a known temperature distribution (N. I. Kömle and G. Dettleff 1991, Icarus 89, 73–84; Yu. V. Skorov et al. 1999, Icarus 140, 173–188). We review briefly the main aspects of this previous work, and subsequently present a combined consistent model, which uses a macroscopic heat transfer equation, but kinetic solutions for the gas flow. This new model was implemented as a numerical code and its performance is demonstrated by a couple of example calculations. The main advantage of the new model in comparison to the macroscopic approach is the fact that it avoids specifying a boundary condition for gas pressure at the surface, because the emitted gas flux is found at any time with the aid of the kinetic calculation. The local balance of sublimation and condensation in the interior of the porous ice can be calculated more consistently than is possible by macroscopic models only, because surface pressure and density develop in a “natural” way and no external boundary condition for the pressure must be imposed. We consider the development of temperature distribution and gas flux in ice samples in response to surface irradiation. Both pure ice and ice covered by a dust mantle are studied. The results are compared with corresponding solutions obtained on the basis of a macroscopic model, and differences are discussed in detail. Finally, experimental data obtained from previous comet simulation experiments (KOSI and related laboratory experiments) are reconsidered. In particular, temperature profiles and gas fluxes from the KOSI-9 experiment (E. Grün et al., 1993, J. Geophys. Res. 98, 15,091–15,104) are interpreted in terms of the kinetic approach.

Studies on high‐speed melt spinning of noncircular cross‐section fibers. III. Modeling of melt spinning process incorporating change in cross‐sectional shape

AbstractA numerical analysis program for high‐speed melt spinning of flat and hollow fibers was developed. Change in cross‐sectional shape along the spin line was incorporated adopting a formulation in which energy reduction caused by the reduction of surface area was assumed to be equal to the energy dissipation by viscous flow in the plane perpendicular to the fiber axis. In the case of flat fiber spinning, the development of temperature distribution in the cross section was considered. It was found that the empirical equations for air friction and cooling of the spin line of circular fibers can be applied for the flat fiber spin line if the geometrical mean of long‐axis and short‐axis lengths was adopted, instead of fiber diameter, as the characteristic length for Reynolds number and Nusselt number. Three features expected through the high‐speed spinning of noncircular cross‐section fibers could be reproduced: (1) although cooling of the flat fiber spin line was enhanced, calculated tension at the position of solidification was not affected much by the difference in cross‐sectional shape; (2) change in cross‐sectional shape proceeded steeply near the spinneret; and (3) temperature at the edge became significantly lower than that at the center in the cross section of flat fibers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1589–1600, 2001

Transient thermal convection in an enclosure induced simultaneously by gravity and vibration

Transient thermal convection in a two-dimensional square enclosure induced simultaneously by gravity and vibration is investigated numerically. The enclosure, which is filled with air under a terrestrial environment, is insulated at both horizontal walls and kept at constant temperature at the vertical walls. For time t=0, the fluid is stationary with the same temperature as the vertical walls T c; as t > 0, the left wall temperature is raised to T h and the enclosure is vibrated with a constant frequency Ω and amplitude b simultaneously. In order to study the effect of vibration frequency on the transient thermal convection, four vibration frequencies (100, 900, 1100, 5000) are considered with fixed Rayleigh number ( Ra=10 4 ) and vibrational Grashof number ( G = 10 6 ). The results show that the transient process, from the stationary state to the steady flow state, is shortened by increasing the vibration frequency, and both the flow field and heat transfer mechanism are mainly determined by the vortex shedding rate, which has the same frequency as the vibration frequency near the upper and lower corners of the hot wall. For ω=100, a single main cell is formed and alternates the rotating direction with the variation of the buoyancy force direction. For ω=5000, the buoyancy force induced by the vibration is definitely dominant and the development of temperature distribution from left to right sides is initially symmetric at the center line of the vertical wall; afterwards, an instability of the thermal boundary layer causes an overshoot of the total Nusselt number and an increase of flow intensity before the periodic solution is approached. For ω=900 and 1100, the vortices shed continuously and alternately from the upper and lower corners near the hot wall, which causes the variation of the total Nusselt number to be irregular and inconsistent on the hot and cold walls for the ω=900 case; for the ω=1100 case the total Nusselt number varies irregularly in the transient processes, but a periodic solution is obtained at steady state.