Heat flux density in 2D simulation

BigBoBy · September 29, 2022, 18:55

I have done a 2D simulation of a rectangular cell. I set a fixed temperature at one wall. Now I want to determine the heat flux density of this wall. To do this, I measured the heat flux of that wall [in W]. How can I now determine the heat flux density [W/m^2]? Becaus in 2D I have only one dimension of the wall because the wall is an edge.

How can ANSYS determine the heat flow of a 2D "surface" at all? Doesn't it need a 3D surface for that?

LuckyTran · September 29, 2022, 20:22

FYI what you are calling heat flux density, everybody else calls heat flux. Heat flux has units of W/m^2 and not W.

Fluent gives you the heat flux on boundaries, it is readily available in a variable called wall heat flux. Just select it.

FVM is always a balance of fluxes going into and out of each computational cell, whether in 2D or 3D. You don't need to worry about how heat flux is obtained because it is a fundamental input to FVM. Actually, you should be more concerned with how Ansys gives you a heat in W because that does depend on an area (that you don't have)! You didn't ask how heat is calculated in a 2D simulation, but the answer is that Fluent takes the heat flux (in W/m^2) and multiplies it by the reference depth which you input in the reference values pane. You can actually get different values for heat rate in W by simply changing the value of the reference depth, but the heat flux will not change.

September 29, 2022, 18:55	Heat flux density in 2D simulation	#1
BigBoBy New Member Bob Join Date: Aug 2022 Posts: 14 Rep Power: 3	I have done a 2D simulation of a rectangular cell. I set a fixed temperature at one wall. Now I want to determine the heat flux density of this wall. To do this, I measured the heat flux of that wall [in W]. How can I now determine the heat flux density [W/m^2]? Becaus in 2D I have only one dimension of the wall because the wall is an edge. How can ANSYS determine the heat flow of a 2D "surface" at all? Doesn't it need a 3D surface for that?

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September 29, 2022, 20:22		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,672 Rep Power: 65	FYI what you are calling heat flux density, everybody else calls heat flux. Heat flux has units of W/m^2 and not W. Fluent gives you the heat flux on boundaries, it is readily available in a variable called wall heat flux. Just select it. FVM is always a balance of fluxes going into and out of each computational cell, whether in 2D or 3D. You don't need to worry about how heat flux is obtained because it is a fundamental input to FVM. Actually, you should be more concerned with how Ansys gives you a heat in W because that does depend on an area (that you don't have)! You didn't ask how heat is calculated in a 2D simulation, but the answer is that Fluent takes the heat flux (in W/m^2) and multiplies it by the reference depth which you input in the reference values pane. You can actually get different values for heat rate in W by simply changing the value of the reference depth, but the heat flux will not change.