Because The Nonisothermal Pipe Flow Interface is a multiphysics interface it shares many nodes with other physics interfaces. These boundary, edge, point, and pair nodes are available as indicated (and listed in alphabetical order).
In the COMSOL Multiphysics Reference Manual see Table 2-4 for links to common sections and Table 2-5 to common feature nodes. You can also search for information: press F1 to open the Help window or Ctrl+F1 to open the Documentation window.