Design and testing of a high speed rotating heat pipe

Rotating heat pipe (RHP) technology development for advanced electrical machine cooling is continuing. The scope of the present research is focused on the cooling of rotors of high speed and high power electrical machines such as switched reluctance and permanent magnet types. Efficient cooling will greatly increase the service life of electrical machines by reducing stresses and high temperature degradation of magnets and insulation besides increasing the bearing life. A research study geared toward improved rotor cooling is being conducted at the Wright Laboratory as part of the Air Force "More-Electric Aircraft" initiative. Low (3500 rpm) and moderate (7000 rpm) speed tests of water and methanol filled RHPs made of stainless steel 316 have been published previously. The same working fluids and materials are being used to maintain continuity in the higher speed (40000 rpm) RHP design also. Design changes and modifications done to the RHP and the test rig to allow high speed testing and operation are discussed in this paper.