The Heat Transfer in Pipes (htp) interface (), found under the Heat Transfer branch () when adding a physics interface, is used to model heat transfer by conduction and convection in pipes and channels of different shapes, where the fluid velocity and pressure fields are known a priori. The interface uses 1D energy balance to determine the temperature profiles on curve segments, or lines. These lines can be drawn in 2D or 3D and represent simplifications of hollow tubes. Wall heat transfer, including multilayer walls and cladding is included as an option.

The Nonisothermal Pipe Flow Interface extends this physics interface by providing equations to compute the velocity and pressure fields when they are unknown.

When this physics interface is added, these default nodes are also added to the Model Builder — Heat Transfer, Pipe Properties, Temperature, and Initial Values. Then, from the Physics toolbar, add other nodes that implement, for example, boundary conditions. You can also right-click Heat Transfer in Pipes to select physics features from the context menu.

The Label is the default physics interface name.

The Name is used primarily as a scope prefix for variables defined by the physics interface. Refer to such physics interface variables in expressions using the pattern <name>.<variable_name>. In order to distinguish between variables belonging to different physics interfaces, the name string must be unique. Only letters, numbers, and underscores (_) are permitted in the Name field. The first character must be a letter.

The default Name (for the first physics interface in the model) is htp.

This physics interface defines the Temperature T (SI unit: K) dependent variable (field). If required, edit the name, but dependent variables must be unique within a model.