comparing two boundary conditions

Sadegh.A · July 21, 2017, 14:29

Hi everybody
I want to simulate a heat exchanger shell and tube type using fluent. Could you please tell me I can use a constant temperature instead of using constant flux when defining boundary conditions on fluent? I mean consider a phase change for gas phase at its dew point and calculating its flow rate using heat flux which is transferred at first condition with constant flux boundary condition in fluent. The target quantity in my study is Nu number and by using this change do you think the value of Nu can change (through some ways like changing thermal boundary layer and …)?
I will appreciate any guidance.

*it may be required:
Water and natural gas are flowing inside tube and shell respectively and this energy transfer can’t cause phase change for water I real conditions.

LuckyTran · July 22, 2017, 02:41

The heat transfer coefficient and Nusselt number do depend on the boundary condition. You should expect very different results for each.

Sadegh.A · July 22, 2017, 15:31

thank you so much for your time dear Lucky
but could i use a completely same case when i want to validate my model (constant heat flux in heat exchanger) and after reaching an acceptable error, in my new study define a constant temperature?
i mean can a model be reliable when you validate it by one type and then you use it with a another one?

July 21, 2017, 14:29	comparing two boundary conditions	#1
Sadegh.A New Member Sadegh Join Date: Oct 2015 Posts: 10 Rep Power: 11	Hi everybody I want to simulate a heat exchanger shell and tube type using fluent. Could you please tell me I can use a constant temperature instead of using constant flux when defining boundary conditions on fluent? I mean consider a phase change for gas phase at its dew point and calculating its flow rate using heat flux which is transferred at first condition with constant flux boundary condition in fluent. The target quantity in my study is Nu number and by using this change do you think the value of Nu can change (through some ways like changing thermal boundary layer and …)? I will appreciate any guidance. *it may be required: Water and natural gas are flowing inside tube and shell respectively and this energy transfer can’t cause phase change for water I real conditions.

July 22, 2017, 02:41		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,761 Rep Power: 66	The heat transfer coefficient and Nusselt number do depend on the boundary condition. You should expect very different results for each. Sadegh.A likes this.

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July 22, 2017, 15:31		#3
Sadegh.A New Member Sadegh Join Date: Oct 2015 Posts: 10 Rep Power: 11	thank you so much for your time dear Lucky but could i use a completely same case when i want to validate my model (constant heat flux in heat exchanger) and after reaching an acceptable error, in my new study define a constant temperature? i mean can a model be reliable when you validate it by one type and then you use it with a another one?