scholarly journals Численное моделирование процесса получения мультикремния методом направленной кристаллизации

2020 ◽  
Vol 90 (7) ◽  
pp. 1080
Author(s):  
С.А. Смирнов ◽  
В.В. Калаев
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Crystal Growth ◽  
Dislocation Density ◽  
Directional Solidification ◽  
Cross Section ◽  
Thermal Stresses ◽  
Vertical Cross Section ◽  
Computational Domain

Numerical simulation of silicon multi-crystal growth by directional solidification with a square crucible is considered. We validate the use of 2D geometry of the vertical cross section as a computational domain. The model describes melt hydrodynamics, global heat transfer, thermal stresses and the evolution of the dislocation density in the crystal. The sensitivity of the stresses and dislocation density in the Si crystal to the parameters of the Alexander-Haazen model is analyzed.

Optimization of Bulk Hgcdte Growth in a Directional Solidification Furnace by Numerical Simulation

1995 ◽  
Vol 398 ◽  
Author(s):  
A.V. Bune ◽  
D.C. Gillies ◽  
S.L. Lehoczky
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Finite Element ◽  
Crystal Growth ◽  
Numerical Model ◽  
Directional Solidification ◽  
Growth Conditions ◽  
Finite Element Code ◽  
Interface Shape ◽  
Solidification Furnace

ABSTRACTA numerical model of heat transfer by combined conduction, radiation and convection was developed using the FIDAP finite element code for NASA's Advanced Automated Directional Solidification Furnace (AADSF). The prediction of the temperature gradient in an ampoule with HgCdTe is a necessity for the evaluation of whether or not the temperature set points for furnace heaters and the details of cartridge design ensure optimal crystal growth conditions for this material and size of crystal. A prediction of crystal/melt interface shape and the flow patterns in HgCdTe are available using a separate complementary model.

Effects of Intersection Angles on Flow and Heat Transfer in Corrugated-Undulated Channels With Sinusoidal Waves

2006 ◽  
Vol 128 (8) ◽  
pp. 819-828 ◽  
Author(s):  
Jixiang Yin ◽  
Guojun Li ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Three Dimensional ◽  
Computational Domain ◽  
Straight Channel ◽  
Flow Area ◽  
Contact Points ◽  
Flow And Heat Transfer ◽  
Different Characteristics ◽  
Steady Laminar

This paper reported three-dimensional numerical simulations of the steady laminar flow and heat transfer in corrugated-undulated channels with sinusoidal waves, aiming to investigate the effects of intersection angles (θ) between corrugated and undulated plate and Reynolds number (Re) on the flow and heat transfer. The simulations are conducted by using multi-channel computational domain for three different geometries. The code is validated against experimental results and then data for Nusselt number (Nu) and friction factor (f) are presented in a Re range of 100-1500, and intersection angle range of 30-150deg. The simulation confirms the changes of Nuu (averaged over undulated plate) and Nuc (averaged over corrugated plate) with θ representing different characteristics. As θ increases, Nu (Nuu or Nuc) is about 2–16 times higher for the corrugated-undulated configurations CP-UH1 and CP-UP1 and the concomitant f is about 4–100 higher, when compared to a straight channel having square cross section. The minimum of local Nu ( Nuu or Nuc ) is situated at the four contact points where the top plate touches the bottom one, and the high Nu is located upstream of the crest of the conjugate duct. Performance evaluation for the CP-UH1 channel shows that the goodness factors (G) are larger than 1 with the straight channel having a square cross section as a reference, and the 30deg geometry channel has optimal flow area goodness.

A DSMC Model on Droplet Clusters to Explore the Limiting Factors of Modified Surfaces Promoting Enhanced Dropwise Condensation

2015 ◽  
Author(s):  
Hector Mendoza ◽  
Van P. Carey
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Limiting Factors ◽  
Future Research ◽  
Computational Domain ◽  
Dropwise Condensation ◽  
Cold Wall ◽  
Ambient Conditions ◽  
Droplet Distribution ◽  
Droplet Sizes

Condensation is a physical process that occurs when a vapor is cooled and/or compressed to its saturation limit. Condensation becomes important in a variety of engineering applications such as in heat exchangers used for distillation purposes. In such instances, higher condensation efficiencies are desirable. Research to improve condensation has focused on dropwise condensation as it has been shown that it can be significantly more efficient than filmwise condensation. Recent investigations of dropwise condensation on nanostructured surfaces suggest that enhanced dropwise condensation can be attained as the average droplet sizes are reduced for clusters growing through dropwise condensation. This, in turn, significantly enhances the heat transfer coefficients of dropwise condensation. This paper summarizes a computational model developed to explore the mechanisms leading to this enhanced dropwise condensation. A Direct Simulation Monte Carlo (DSMC) approach is used here to investigate the mechanisms and limitations of enhanced dropwise condensation for these surfaces aiming to reduce the average droplet sizes of condensation. For computational purposes, several idealizations are assumed by the model, which include: (1) The condensation droplet clusters are assumed to have uniform size, corresponding to an average droplet size observed in actual dropwise condensation scenarios; (2) Due to the assumed uniform droplet distribution, symmetry can be observed from the droplet cluster, so a small but symmetrical cross section of the droplet distribution is used for the computational domain; and (3) Supersaturated steam condensing on a cold wall is assumed for most of the simulations. The mechanisms at play that are deliberately explored are: (1) The effects of surface wettability by using a model that considers droplet conduction variations with varying contact angle; (2) The changes of interfacial resistance with droplet curvature by introducing a surface tension model based on the Tolman length; and (3) The dynamic interactions between neighboring droplets by choosing our computational domain to be a symmetrical cross section that encompasses surrounding droplets in an appropriate fashion. The ambient conditions that were investigated were: (1) Varying atmospheric pressure; (2) Varying amounts of wall subcooling for the droplets; (3) Varying accommodation for water molecules condensing on the droplet; and (4) The introduction of air into the assumed supersaturated steam condensing on the cold wall. To investigate the overall and combined effects of the aforementioned mechanisms on enhanced dropwise condensation through reduced droplet sizes, the simulations were run for droplets with radii between 1 micrometer down to 5 nanometers. The model predictions indicate that the larger droplet transport trend of increasing heat transfer with decreasing droplet sizes breaks down as droplet sizes become smaller due to more prominence of the mechanisms hindering condensation for the reduced droplet sizes. As the model breaks down, a peak heat transfer is reached, and heat transfer is further reduced as the average droplet sizes continue to decrease. The predictions of this particular DSMC model are compared to previous work investigating similar effects. The implications of our observations and potential impact to current and future research in the area is discussed in detail.

Numerical Investigation of Natural Convection Heat Transfer from Square Cylinder in a Vented Enclosure

2011 ◽  
Vol 110-116 ◽  
pp. 4451-4464 ◽  
Author(s):  
Ghalib Y. Kahwaji ◽  
Abbas S. Hussien ◽  
Omar M. Ali
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Cross Section ◽  
Convection Heat Transfer ◽  
Grid Generation ◽  
Flow Patterns ◽  
Horizontal Cylinder ◽  
Natural Convection Heat Transfer ◽  
Computational Domain ◽  
Convection Heat

In the present work, the natural convection heat transfer from horizontal cylinder with square cross section situated in a square enclosure, vented symmetrically from the top and the bottom was investigated numerically. The work investigate the effect of the Ra, enclosure width and opening size of the enclosure on the streamlines, isotherms and heat transfer results. The numerical work included the solution of the governing equations in the vorticity-stream function formulation which were transformed into body fitted coordinate system. The transformations are based initially on algebraic grid generation and elliptic grid generation to map the physical domain between the heated horizontal cylinder and the vented enclosure into a computational domain. A hybrid scheme finite volume based finite difference method was used. The study included the following ranges of the studied variables:- 0 < Ra ≤ 6.5× 105 1.5 ≤ W/H ≤ 4 0.375 < O/H ≤ 4 The numerical results were compared with experimental results, which showed good agreement. The effect of cylinder cross section, Ra, enclosure width, and opening size on the Nu, mass flowrate, flow patterns and isotherms were investigated. The results show that the cylinder cross section has a large influence on the results especially the Nu. The Nu is proportional with Ra and inversely proportional with enclosure width and opening size. The flow patterns and isotherms display the flow and temperature behaviors with changing studied variables. The results show that the starting of natural convection heat transfer depended on the cylinder cross-section, enclosure width and opening size in addition with Ra. In addition, the results display that the hydrodynamic and thermal boundary layer thickness decreases with increasing Ra. Nomenclature

Laminar Convection on a Vertical Heated Plate Placed in a Chimney

Volume 1 ◽  
2004 ◽  
Author(s):  
A. Farber ◽  
V. Dubovsky ◽  
G. Ziskind ◽  
R. Letan
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Image Processing ◽  
Cross Section ◽  
Computer Simulations ◽  
Video Recording ◽  
Temperature Fields ◽  
Heated Plate ◽  
Horizontal Cross Section ◽  
Laminar Convection

This study deals with heat transfer from a vertical electrically heated plate, which is symmetrically placed in an experimental modular chimney of variable height. The chimney is made of Perspex in order to enable observation and recording of the flow. The inner horizontal cross-section of the chimney is a rectangle, 110 by 20 mm, where the larger dimension is along the plate and the smaller one is normal to it. Three main approaches are used in parallel: temperature measurement, flow visualization, and numerical simulation. Temperature measurements are done by thermocouples distributed inside the plate and through the chimney. Visualization is performed using the smoke of incense sticks, with video recording and consequent image processing. It indicates that the flow inside the chimney remains laminar under the conditions of the present study. Computer simulations of flow and temperature fields are performed in 3D and compared with the measurements and visualization.

scholarly journals Numerical Simulation and Experimental Observations of Confined Bubble Growth During Flow Boiling in a Microchannel With Rectangular Cross-Section of High Aspect Ratio

2009 ◽  
Author(s):  
Y. Q. Zu ◽  
S. Gedupudi ◽  
Y. Y. Yan ◽  
T. G. Karayiannis ◽  
D. B. R. Kenning
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Fluid Mechanics ◽  
Cross Section ◽  
Flow Boiling ◽  
Rectangular Cross Section ◽  
Pressure Fluctuations ◽  
High Heat ◽  
Inlet Flow ◽  
Bubble Liquid

Bubble nucleation and growth to confinement during flow boiling in microchannels lead to high heat transfer coefficients. They may also create pressure fluctuations that change the superheat driving evaporation and cause flow reversals that promote transient dry-out and uneven distribution of flow between parallel channels. The work described in this paper is part of a programme to develop models for these processes that will aid the design of evaporative cooling systems for devices operating at high heat fluxes. Video observations of water boiling in a single copper channel of rectangular cross-section, 0.38 × 1.6 mm and a heated length 40 mm, were performed. The top side of the channel was a glass window. Results are presented for a heat flux, averaged over the area of the three metal sides, of 210 and 173 W/m2K for incompressible and compressible inlet flow conditions. The inlet pressure was about 1.12 bar and the mass flux was 747.5 kg/m2s for both conditions examined. The results demonstrated the strong influence of compressibility on the mode of bubble detachment and growth and therefore on flow patterns, pressure fluctuations and heat transfer rates. The fluid mechanics of boiling in this size channel were also successfully investigated by 3-D numerical simulation for bubbles growing at a defined rate with a fixed inlet flow rate using the 3-D CFD code FLUENT 6 (no upstream compressibility). The study examined the fluid mechanics of bubble motion with heat transfer, but the mass transfer across the bubble-liquid interface was not simulated in the present work. A small vapour bubble was injected at the wall to ensure the bubble generation is under a quasi nucleation condition. Its growth was driven by an internal source of vapour, at a rate derived by analysis of the experimental measurements of growth. The simulation reproduced well the observed motion and shape of the bubble. The simulation was then extended to model bubbles generated and growing randomly in a 2-D channel.

Sign in / Sign up

Export Citation Format

Share Document