Avi Friedman Master’s Student Mechanical Engineering Room: 1337 ERB Hometown: Owings Mills, MD Thesis: Design and Development of a Next Generation High Capacity, 20K Pulse Tube Cryocooler

Motivation Currently, space cryocooling limitations exist due to the lack of high capacity, low temperature, and highly efficient cryogenic cooling systems. In particular, current state-of-the-art 20 Kelvin cryocoolers have a heat load capacity of 1 Watt at 20 Kelvin with a specific power of 180 W/W. However, 20 Kelvin cryocoolers with a heat load capacity of at least 20 Watts, with a specific power of approximately 100 W/W, will be required for future exploration missions.

What is a Pulse Tube Cryocooler? Advantages over other cryocoolers: Operates at low frequency's Capable of high efficiency's No moving parts at the cold end How it works: On one end Helium (He) is compressed and heat is rejected in the aftercooler. On the other end the pulse tube acts as a piston and expands the He which then passes through the cold heat exchanger (HX) and cools the load. The regenerator accepts or rejects heat from/to the He depending on the stage in the cycle. The inertance tube and reservoir keep the pressure in the correct phase with the mass flow rate.

Objectives Thoroughly design and parametrically study, a complete two-stage pulse tube cryocooler (PTC) with a 5W or larger cooling capacity at 20K Perform an in-depth investigation of the regenerators at pore and component levels, particularly with regards to the lower temperature stage regenerator which will contain filler material made from rare Earths (Er0.5-Pr0.5, for example) Fabricate and test the most critical components of the system such as the regenerator and the pulse tube for thermodynamic and structural performance Perform an in-depth experimental analysis of the critical components Fabricate and test a prototype of the designed 5 W at 20 K cryocooler in its entirety Concurrently with the design/demonstration/fabrication of the 5 W, 20 K cryocooler, thoroughly design and theoretically demonstrated a 20 W 20 K pulse tube cryocooler