Model and Test of an Actively Controlled Cryogenic Micro Valve

Under the supervision of Professor Gregory F. Nellis; 159pp.Future NASA missions require cooling of large optical structures, cryogen storage systems, and instrument chambers and therefore cooling must be applied in a controlled and efficient fashion over a large spatial extent. A cooling system that uses an actively controlled, micro-scale valve may be integrated with heat exchangers and sensors in order to allow the individual branches of a distributed cooling system to be independently controlled in response to local temperature changes. The ability to control the flow area associated with the valve increases the efficiency and flexibility of the distributed cooling system by allowing the cooling to be concentrated according to need. Previous work has selected a suitable micro valve design that addresses the required specifications. However, the precise nature of the flow behavior inside the micro valve was not addressed. Therefore, this thesis focuses on the modeling and test of the pressure-flow behavior of a micro-scale valve over a range of operating conditions. Variable voltage actuation of the PZT actuator within the micro-valve modulates the flow area and therefore the pressure distribution and fluid flow behavior. Fluid-structure models were developed to predict the pressure distribution and flow rates. Experimental data from prototype micro valves was used to validate the analytical predictions