Thermal Expansion (for Materials)
Use the Thermal Expansion subnode to add an internal thermal strain caused by changes in temperature. The thermal strain depends on the coefficient of thermal expansion (CTE) α, the temperature T, and the strain-free reference temperature Tref as
The average increase in temperature will cause a global extension of the pipe, whereas a difference between the internal and internal temperature will cause local bending stresses.
Model Inputs
The Volume reference temperature Tref is the temperature at which there are no thermal strains. As a default, the value is obtained from a Common model input. You can also select User defined to enter a value or expression for the temperature locally.
The Temperature, T, input is not used. All temperature information is taken from the inputs in the Thermal Expansion Properties section. This field will, for formal reasons, be visible in the GUI indicating when the selected material has a temperature dependent coefficient of thermal expansion.
Thermal Expansion Properties
Specify the thermal properties that define the thermal strain.
From the Coefficient of thermal expansion α list, select From material to use the coefficient of thermal expansion from a material, or User defined to enter a value or expression for α. When From material is used, then you need to specify which material to use by selecting a Pipe material. This list contains all materials present in the component, as well as the default choice Edge material. When Edge material is selected, the material currently assigned to the edge (2D: boundary) is used.
Enter the Inside temperature, Tin, and Outside temperature, Tout.
The temperature difference in the thickness direction is computed, using Wall Heat Transfer in the Heat Transfer in Pipes interface. In this case, use the User defined option, and enter the variables defined in the Wall Layer node the for the inner and outer temperatures. These variables typically have names like htp.wht1.wall1.Tin and htp.wht1.wall1.Tout.
Default Model Inputs and Model Input in the COMSOL Multiphysics Reference Manual.
Location in User Interface
Context Menus
Ribbon
Physics tab with Fluid and Pipe Materials node selected in the model tree: