high LHTC values in Coolant jacket analysis

rcm · November 3, 2010, 04:31

hello all,

I'm doing analysis of water jacket of crankcase and cylinder head of multicylinder diesel engine. i am using polyhedral cells with prism layer at wall. y+ is maintained between 10 to 125 .

The problem is i'm getting very high values of HTC's . it goes up to 60000 W/m2k in region where velocities are 4m/s to 6m/s . i am using realizable k-e all y+. i get same values when i use high y+ wall treatment.

has anyone come across such high values of HTC? or does anyone knows what could be the possible reason?

HTC in coolant jacket analysis should not exceed 20000 W/m2K

RobertB · November 3, 2010, 07:13

Do you have the heat transfer reference temperature set to something sensible?

I assume you have checked the fluid properties to make sure all the values are credible.

rabat · November 4, 2010, 02:43

Do you have locally high LHTC?
Normally I have by 5m/s ~ 25000W/m^2.K.
Are the residuals ok? 10^-4
Your calculation is isothermal or segragated fluid temperatur?

rcm · November 7, 2010, 23:46

Hi RobertB,
Thanks for reply
I'm checking only Local heat transfer reference temperature.. it doesnt require to set up the referance temperature.. anyways the heat transfer referance temperature is set to 90 deg C that is inlet temperature of coolant. fluid properties are also correct.

rcm · November 8, 2010, 00:09

Hi rabat,
Thanks for reply
velocities goes above 5m/s and they are up to 7m/s and at some small region it goes up to 8m/s. i have given fixed temperature at wall but i have segregated fluid temperature model on. when u do reset to restart in CCM+ resudual starts from 1 so i cant really tell whether its below 1e-4. its converged and residuals have constant value

abdul099 · January 6, 2011, 18:16

Not sure whether it's the same issue, but in external aero calculations, the Y+ range from lets say 5 to 25 should be avoided when possible. Even with the all Y+ turb model, because this is just blending the high Y+ model and the low Y+ model according to the Y+ value. It's better than using one of the two other models, but it will not create miracles.

rabat · January 12, 2011, 13:57

Hello,

I've never get high HTC, my quetions are:

How many prism layers do you have?
How wide the prism layer thickniss?

Rabat

MBA · January 15, 2011, 01:21

Hello ,

How did you calculate HTC?

November 3, 2010, 04:31	high LHTC values in Coolant jacket analysis	#1
rcm New Member chetan Join Date: Apr 2010 Posts: 11 Rep Power: 16	hello all, I'm doing analysis of water jacket of crankcase and cylinder head of multicylinder diesel engine. i am using polyhedral cells with prism layer at wall. y+ is maintained between 10 to 125 . The problem is i'm getting very high values of HTC's . it goes up to 60000 W/m2k in region where velocities are 4m/s to 6m/s . i am using realizable k-e all y+. i get same values when i use high y+ wall treatment. has anyone come across such high values of HTC? or does anyone knows what could be the possible reason? HTC in coolant jacket analysis should not exceed 20000 W/m2K

November 4, 2010, 02:43	high LHTC values in Coolant jacket analysis	#3
rabat New Member Join Date: Mar 2009 Location: Belgium Posts: 13 Rep Power: 17	Do you have locally high LHTC? Normally I have by 5m/s ~ 25000W/m^2.K. Are the residuals ok? 10^-4 Your calculation is isothermal or segragated fluid temperatur?

January 12, 2011, 13:57	high LHTC values in Coolant jacket analysis	#7
rabat New Member Join Date: Mar 2009 Location: Belgium Posts: 13 Rep Power: 17	Hello, I've never get high HTC, my quetions are: How many prism layers do you have? How wide the prism layer thickniss? Rabat

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November 3, 2010, 07:13		#2
RobertB Senior Member Robert Join Date: Jun 2010 Posts: 117 Rep Power: 17	Do you have the heat transfer reference temperature set to something sensible? I assume you have checked the fluid properties to make sure all the values are credible.

November 7, 2010, 23:46		#4
rcm New Member chetan Join Date: Apr 2010 Posts: 11 Rep Power: 16	Hi RobertB, Thanks for reply I'm checking only Local heat transfer reference temperature.. it doesnt require to set up the referance temperature.. anyways the heat transfer referance temperature is set to 90 deg C that is inlet temperature of coolant. fluid properties are also correct.

November 8, 2010, 00:09		#5
rcm New Member chetan Join Date: Apr 2010 Posts: 11 Rep Power: 16	Hi rabat, Thanks for reply velocities goes above 5m/s and they are up to 7m/s and at some small region it goes up to 8m/s. i have given fixed temperature at wall but i have segregated fluid temperature model on. when u do reset to restart in CCM+ resudual starts from 1 so i cant really tell whether its below 1e-4. its converged and residuals have constant value

January 6, 2011, 18:16		#6
abdul099 Senior Member Join Date: Oct 2009 Location: Germany Posts: 636 Rep Power: 22	Not sure whether it's the same issue, but in external aero calculations, the Y+ range from lets say 5 to 25 should be avoided when possible. Even with the all Y+ turb model, because this is just blending the high Y+ model and the low Y+ model according to the Y+ value. It's better than using one of the two other models, but it will not create miracles.

January 15, 2011, 01:21		#8
MBA New Member anonymous Join Date: Oct 2010 Posts: 4 Rep Power: 16	Hello , How did you calculate HTC?