[ashraf88]

Hi every one,

Task: Modeling a cross flow in a staggered tube bundle using ANSYS CFX.

Given: The fluid is water of 300 deg Clausius flowing with inlet velocity 1 m/s,the boundary conditions are defined very well.

Problem: The results shows that water temperature is not changing along the domain; water temp. inlet same as outlet.

So I am not sure about the reason of that, Turbulence model, or water velocity, Heat transfer mode ( Total energy or Thermal Energy) ?

Please help me .

[ghorrocks]

First of all, please do not hijack threads. Start a new thread for a new question - especially when your question is not related to the original thread.

This problem could be caused by many things - it could be inaccuracy in your simulation (see http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F for tips) or it could be that the setup you are modelling does not result in significant heat being transferred to the water. From the sketchy details you have posted I cannot tell.

Also - are you sure you are using a thermal model? You would not get any heat transfer if you have not enabled thermal modelling. Also how have you modelled the tube bank?

[ashraf88]

Originally Posted by ghorrocks

First of all, please do not hijack threads. Start a new thread for a new question - especially when your question is not related to the original thread.

This problem could be caused by many things - it could be inaccuracy in your simulation (see http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F for tips) or it could be that the setup you are modelling does not result in significant heat being transferred to the water. From the sketchy details you have posted I cannot tell.

Also - are you sure you are using a thermal model? You would not get any heat transfer if you have not enabled thermal modelling. Also how have you modelled the tube bank?

Dear ghorrocks,
I really appreciate your replay, I am so sorry that i didn't started a new thread.
I am sure that I am using the thermal modeling. But what I am not sure about is that may be I didn't make the setup well.
The tube bank is modeled as a cylinders, not Conjugate heat transfer
Thanks so much for your kind response

[ghorrocks]

Can you post an image? Also your CCL would help.

[Mr Torabi]

Hello everybody
I want to do a simulation of a turbulent cross flow over a inline tube bank with ansys CFX. my material is a mixture of ideal gases(H2O & CO2 & N2). after simulation, results show me that dynamic viscosity and thermal conductivity don't change with temprature even when the tubes temperature have magnificent difference with inflow temperature.
in fact at any temperature:

massFlowAve (Thermal Conductivity)@ Inlet= massFlowAve (Thermal Conductivity)@Outlet

and


massFlowAve(Dynamic Viscosity)@ Inlet= massFlowAve(Dynamic Viscosity)@Outlet


in material section , i select the " Fixed composition mixture" for option part and "Gas phase combustion" for material groups.

key features are
- 2D-channel
- symmetry BC at all walls besides inlet, outlet and tube walls (no-slip walls)
- Thermal energy for heat transfer option
- steady-state

I would be very grateful for every hint, where the error might be. If you need more informations just tell me.

Thanks

[evcelica]

Well, I would guess that the materials in your mixture all have constant values for thermal conductivity and viscosity by default. You would have to change them to be temperature dependent if you want your mixture to also have temperature dependent properties.
Check the material properties.

[Mr Torabi]

Originally Posted by evcelica

Well, I would guess that the materials in your mixture all have constant values for thermal conductivity and viscosity by default. You would have to change them to be temperature dependent if you want your mixture to also have temperature dependent properties.
Check the material properties.

yeah. the properties of components were constant and didn't change with temperature. i fixed it

thanks for your hint