
[Sponsors] 
June 27, 2012, 04:23 
VOF Boiling

#1 
New Member
Join Date: Oct 2011
Posts: 20
Rep Power: 7 
Hello friends,
As a part f my project, I simulate HTC with Boiling model. I have experiment results and I am gong to validate the experiment using starccm+ 7.0.2. I have a solid domain which is aluminium and fluid domain waterglycol. Solid domain has a constant temperature which is higher than boiling temperature. Boiling model is going to have a liquid phase as waterglycol mixture and gas phase as a water steam. I use VOF > Rohsenow Boiling model. I have two doubts regarding my simulation. 1) Liquid Phase Material Properties Let's say mixture of T_inlet=90 C and T_boiling= 120 C, V_inlet = 1 m/s at 1 atm in the simulation. Which temperature I am going to use to determine my material poperties of liquid phase? What should I use for Standard State Temperature value under properties list? Gas phase material properties are simply because T_boiling (or T_saturation) is going to be used obviously. 2) I searched literature of Rohsenow boiling. I have good guesses for Exponential Prandl number and C_qw parameter. However, I do not know exactly what HTCxArea means and how can I adjust it for my silmulation. Could someone explain a little bit? Regarding the issues mentioned above, I kindly request some advice from you. Any help would be appreciated. Kind regards 

July 25, 2012, 17:57 

#2 
New Member
Join Date: Oct 2011
Posts: 20
Rep Power: 7 
Still no reply on HTCxArea ??


August 7, 2012, 09:33 

#3 
New Member
Felix
Join Date: Aug 2012
Posts: 7
Rep Power: 6 
HTCxArea: I have tried for the fluid properties p=1 bar at saturation temperature
First I calculate the diameter of a vapour bubble (Bubble Departure Diameter with a contact angle of 45 ° for water) d= 0.0149 * contact angle * Sqrt((2*surface tension)/(gravity*(Density_liquid  Density_gas))) Then I calculate the surface and the volume of a ball Surface / Volume is the contact area per volume [m²/m³] For the Heat transfer coeffizient I used a Forced convection over a ball. For Re<0.1 Nusselt Number=2 Where do you find your saturation temperature of water glycol? What's your guesses for Exponential Prandtl number and C_qw? Please send! 

August 8, 2012, 04:35 

#4 
New Member
Join Date: Oct 2011
Posts: 20
Rep Power: 7 
Hello Felix,
Thank you for your reply. I am confused, you wrote what you did for your case but you did not mention how (or from which resource) did you calculate HTCxArea value? Could you explain it more? Which value did you use? Default value is given as 5000000. You can find easily saturated temperature of mixtures from heat transfer books for different mixture rates. Just google it. For Exponential Prandtl number and C_qw, they are strongly dependent on your materials. Again you need to find them in literature. You can find small table in Incorpera's Heat Transfer Book. Edit: I do understand your calcuation. Temperature has a great influence on bubble diameter and heat transfer coefficient.Using field function can be a good idea. Last edited by rawe666; August 8, 2012 at 07:22. 

August 9, 2012, 01:24 

#5 
New Member
Felix
Join Date: Aug 2012
Posts: 7
Rep Power: 6 
Here's the source book for the Rohsenow model. You can download it for free from MIT!
http://dspace.mit.edu/handle/1721.1/61431 Page 3 diameter of the bubble as it leaves the surface (eqn 3) Page 4 Bubble Reynolds number and bubble nusselt number (eqn 7 and 8) Page 5 Contact Angle beta for eqn 3 (eqn 11) This one the right for c_qw and exponential prandtl number? http://books.google.at/books/about/I...AJ&redir_esc=y could you be more precise for the book for saturation temperature? I need also data for waterglycol mixtures 

August 10, 2012, 04:09 

#6 
New Member
Join Date: Oct 2011
Posts: 20
Rep Power: 7 
Thank you for your explanation.
Last edited by rawe666; August 28, 2012 at 08:02. 

Tags 
boiling, material properties, rohsenow, vof 
Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Nucleate boiling using VOF  Akash  FLUENT  6  June 27, 2011 07:22 
Eulerian or VOF in boiling?  hamdy  FLUENT  0  February 20, 2011 09:34 
Boiling using VOF  asaleghahreman  FLUENT  2  May 8, 2010 13:32 
Using VOF for sloshing airwater boiling system  Dibakar Rakshit  FLUENT  0  March 12, 2008 08:40 
VOF vs BOILING  greg  FLUENT  0  April 1, 2007 10:59 