0
RESEARCH PAPERS: Processes Equipment and Devices

Numerical Studies on Channel Formation and Growth During Solidification: Effect of Process Parameters

[+] Author and Article Information
Jayesh Jain, Arvind Kumar

Department of Mechanical Engineering, Indian Institute of Science, Bangalore 560012, India

Pradip Dutta1

Department of Mechanical Engineering, Indian Institute of Science, Bangalore 560012, Indiapradip@mecheng.iisc.ernet.in

1

Corresponding author.

J. Heat Transfer 129(4), 548-558 (Oct 13, 2006) (11 pages) doi:10.1115/1.2709660 History: Received February 11, 2006; Revised October 13, 2006

In the present work, solidification of a hyper-eutectic ammonium chloride solution in a bottom-cooled cavity (i.e. with stable thermal gradient) is numerically studied. A Rayleigh number based criterion is developed, which determines the conditions favorable for freckles formation. This criterion, when expressed in terms of physical properties and process parameters, yields the condition for plume formation as a function of concentration, liquid fraction, permeability, growth rate of a mushy layer, and thermophysical properties. Subsequently, numerical simulations are performed for cases with initial and boundary conditions favoring freckle formation. The effects of parameters, such as cooling rate and initial concentration, on the formation and growth of freckles are investigated. It was found that a high cooling rate produced larger and more defined channels which are retained for a longer durations. Similarly, a lower initial concentration of solute resulted in fewer but more pronounced channels. The number and size of channels are also found to be related to the mushy zone thickness. The trends predicted with regard to the variation of number of channels with time under different process conditions are in accordance with the experimental observations reported in the literature.

FIGURES IN THIS ARTICLE
<>
Copyright © 2007 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 1

Problem domain with initial and boundary condition

Grahic Jump Location
Figure 2

Variation of Ra number with concentration gradient in the direction of plume growth for R=6×10−6m∕s, G=7.7K∕mm, r=0.046K∕s

Grahic Jump Location
Figure 3

Variation of Ra number with liquid fraction for R=6×10−6m∕s, G=7.7K∕mm, r=0.046K∕s

Grahic Jump Location
Figure 4

Variation of Ra number with concentration gradient in the direction of plume growth for different growth rates (R=6×10−6m∕s, G=7.7, K∕mm, fl=0.85, r=0.046K∕s)

Grahic Jump Location
Figure 5

Variation of Ra number with concentration gradient in the direction of plume growth for different Sc number (R=6×10−6m∕s, G=7.7K∕mm, fl=0.85, r=0.046K∕s)

Grahic Jump Location
Figure 6

Comparison of predicted Liquidus and solidus position with time from experimental results of Tan (11)

Grahic Jump Location
Figure 7

Predicted liquid concentration plots: (a) r=0.046K∕s, (b) r=0.15K∕s and temperature distribution in K, (c) r=0.046K∕s; and (d) r=0.15K∕s at t=15s for different cooling rates (Ci=68%, Tb=279K, G=7.7K∕mm)

Grahic Jump Location
Figure 8

Predicted solid fraction plot at t=50s for different cooling rates: (a) r=0.046K∕s; and (b) r=0.15K∕s (Ci=68%, Tb=279K, G=7.7K∕mm)

Grahic Jump Location
Figure 9

Number of channels versus time for different cooling rates (Ci=68%, Tb=279K, G=7.7K∕mm)

Grahic Jump Location
Figure 10

Variation of solute (water) concentration and in the channel and in a location where there is no channel at t=70s: (a) for r=0.046K∕s; and (b) r=0.15K∕s

Grahic Jump Location
Figure 11

Predicted solid fraction plot (a) at t=590s and r=0.046K∕s; (b) at t=270s and r=0.15K∕s (Ci=68%, Tb=279K, G=7.7K∕mm)

Grahic Jump Location
Figure 12

Number of channels versus time for different initial concentration of solute (Tb=279K, r=0.15K∕s)

Grahic Jump Location
Figure 13

Solidus and liquidus position with time for different initial concentration: (a) 75%; and (b) 68% (Tb=279K, r=0.15K∕s)

Grahic Jump Location
Figure 14

Predicted solid fraction plot at t=270s: (a) Ci=75%; and (b) Ci=68% (Tb=279K, G=7.7K∕mm, r=0.15K∕s)

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In