Definition Of Heat Flux In ANSYS® Thermal Analyses
ANSYS® provides lots of tools for solving problems of thermal conditions. In most thermal analyses, convection is a very important variable. In CAE analyses, convection can be also defined as a boundary condition. Here, we explain how to define convection in ANSYS® Mechanical as a boundary condition.
Convection is an actual physical phenomenon that heat flux between faces of bodies or directly faces themselves to a fluid environment. So, if we think that gases are fluid, the heat flux between objects and the atmosphere can be classified as convection.
The explanation of convective heat transfer based on maths is very simple. This explanation is also called Newton’s Law Of Cooling. Convection is a very basic formula;
q/A = hx(Ts-Tf)
In this formula, ‘q’ is heat flux has the unit of ‘W/m2’. ‘A’ is the are of plate or face which has the unit of ‘mm^2 or m^2’. ‘h’ is the film coefficient of material and ambient which has the unit of ‘W/(m2•K)’.
Ts is the surface temperature of the plate or face which is desired to be in Kelvins. And Tf is the fluid temperature.
You can define convection in these types of analyses in ANSYS®; Steady-State, Transient Stress and Thermal Electric analyses.
To define convection to a body or part, just right-click on the analysis which is ‘Steady-State’ in the above example. Inside ‘Insert’ click on ‘Convection’ in ANSYS® Mechanical.
And select the geometries that you want to define your convection as shown above. Then click ‘Apply’ as shown by the red arrow above.
You need to define the ‘Film Coefficient’ and ‘Ambient Temperature’ values as shown in the red box above. You can define these values as ‘Constant’, ‘Tabular’ or ‘Function’.
You can directly enter the constant value inside the boxes.
To define these values as ‘Tabular’, select the ‘Tabular’ option from the pop-up menu as shown by the red arrow above in ANSYS® Mechanical.
If you select ‘Tabular’ option as shown by red arrow above, you need to enter time and ‘Convection’ and ‘Ambient Temperature’ values that correspond to this entered times, at that tabular data in ANSYS®.
You can also define these values as ‘Function’, which you need to type the function by using ‘time’ as a function variable. You can see the all values for each time step. You can change these time steps also by changing ‘Number Of Segments’.
These are the general information about the definition of convection on a body in ANSYS® Mechanical.
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NOTE: All the screenshots and images are used for educational and informative purposes. Images used courtesy of ANSYS, Inc.