SUBJECT: M.S. Thesis Presentation
BY: Caleb Amy
TIME: Monday, July 24, 2017, 2:00 p.m.
PLACE: MRDC Building, 4211
TITLE: Liquid Metal Pumps for Enabling Heat Transfer at Extreme Temperatures
COMMITTEE: Dr. Asegun Henry, Chair (ME)
Dr. Devesh Ranjan (ME)
Dr. Shannon Yee (ME)
Dr. Samuel Graham (ME)


Thermal energy is fundamental to most power generation and many industrial processes, and because of the entropy associated with it, is the most valuable at the highest temperature. To use this heat, it must be transported and molten metals are an ideal heat transfer media because they can have high temperature stability and high heat transfer coefficients. The ability to pump a fluid is key because it enables circulation and includes the thermal and chemical constraints seen by an entire system, with the added challenge of dynamic sealing, stress, and wear.

In this thesis, the first successful demonstration of an all-ceramic mechanical pump is reported. The pump was used to continuously circulate liquid tin (Sn) at a flow rate between 24-108 g/s and a temperature of ~1200°C, in an all ceramic circulation loop, for 72 hours without failure. Here, an aluminum nitride/boron nitride composite, known as Shapal, was used to fabricate an external gear pump, which relied on a graphite packing dynamic seal. Another pump was made from tungsten, which can be used in direct contact with Sn. This pump has so far only been tested to 650°C for eight hours, but it is expected to perform well at 1350°C, and even much higher temperatures.

The pump system includes a shaft actuation system, which tolerates misalignment from thermal expansion and enables thermal separation of the motor. Further, the design and modeling of a circulation loop, weight based and visual flow meter, and extreme temperature thermal management system is discussed. All these components were fabricated from graphite, including seals. The system was held in an inert nitrogen environment to prevent oxidation. Although the pump did not mechanically fail in the reported tests, it did experience significant wear, which resulted in performance degradation. Suggestions for future design improvements to resolve this issue and broaden the capabilities of the system are also included.