COMSOL 6.2 - Thermal Expansion (for Materials)

Thermal Expansion (for Materials)

Use the 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.


	The effects of a thermal gradient through the pipe wall is only taken into account for the Circular Section.

Model Inputs

The Tref is the temperature at which there are no thermal strains. As a default, the value is obtained from a . You can also select to enter a value or expression for the temperature locally.

The , T, input is not used. All temperature information is taken from the inputs in the 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 α list, select to use the coefficient of thermal expansion from a material, or to enter a value or expression for α. When is used, then you need to specify which material to use by selecting a . This list contains all materials present in the component, as well as the default choice . When is selected, the material currently assigned to the edge (2D: boundary) is used.

Enter the , Tin, and , Tout.

If the temperature is computed in the Heat Transfer in Pipes interface, there are two fundamentally different cases:

•

The temperature gradient in the thickness direction is ignored. In this case you can use the temperature of the fluid as both inner and outer temperature, assuming that the temperature of the pipe is the same as that of the fluid. You can then select the temperature degree of freedom from the drop-down menus, typically .

•

The temperature difference in the thickness direction is computed, using in the Heat Transfer in Pipes interface. In this case, use the option, and enter the variables defined in the node the for the inner and outer temperatures. These variables typically have names like htp.wht1.wall1.Tin and htp.wht1.wall1.Tout.