To build models with convection contact, you’ll first need to define the masses or volumes of your non-dimensional masses (e.g. air masses). Bring your model into FEM Builder and then create a new physical property (Menu / Create / Physical Properties). Give it a unique Property ID, any name, and then select either Mass or Volume as the type (you only need one, just use whichever is easier). Enter the value for the parameter and then hit OK.
Next, you need to create a material for the 0D elements(Menu / Create / Material Properties). Give it a name and a unique ID,and then press OK to go to the property entry screen. Select Thermal as the Class, and then select Specific Heat and enter the appropriate value. If you chose to create your physical property based on the mass of the air, you’ll also need to create a Density property. When you’re done creating these, press OK.
Then you need to define your 0D elements. Create one new node in the model for each air mass (it doesn’t matter where they go as long as they’re not touching any other elements). Then create 0D point elements on each of those nodes using the Property ID and Material ID you selected above (Menu / Create / Element, Geometry = Point, Analysis Type =anything, enter label, press OK).
Now you need to define data for the convection between the2D or 3D faces in your model and the 0D element. First, create a new face group that contains only the 0D element face (Menu / Create / Group / Face, pick the 0D elements, Next, give it a unique name, Finish). Then, you need to create a new material property that captures the convection heat transfer coefficient (Menu / Create / Material Properties, enter unique name, enter unique ID, OK, Class = Thermal, Type = Convection Heat Transfer Coefficient, enter value, OK).
Then, you need to define convective contact between the 0Delement and the 2D/3D faces in the model. First create a new thermal interaction that references the material with the convective heat transfer coefficient created above (Menu / Create / Contact / Thermal Interaction, enter a unique name, check Allow Hero Contact, Analysis Type = Temperature, Gap Material = the material with the convection heat transfer coefficient, give it a max projection distance > the maximum gap size, OK). Then, create the contact pairs that connects them together (Menu / Create / Contact /Contact Pair, Face Group = the face group on the 0D element, Slave Surface =the 2D/3D element faces, Next, Contact Model = Thermal, Contact Interaction Data = the thermal interaction data you created above, Finish, repeat for other2D/3D face groups).
Finally, you probably want to define some sensors on the 0Delements so you can easily plot their temperatures (Menu / Create /Instrumentation / Result Sensor, Result Type = Temperature, Name = a unique name, Origin = node location for the 0D element, OK, repeat for other 0Delements).