A Microfabricated Flow Controller for Refrigerant Expansion

A flow controller for refrigerant expansion is reported. Devices are fabricated using a micromolding technique that is developed for thick nickel electrodeposition. The device consists of a short-tube restrictor with an integrated normally open valve, which, when actuated, presents a controllable blockage into the flow passage to obstruct the flow. Fabricated devices are evaluated with compressed air, with up to 22% reduction in mass flow rate at maximum actuation of the restrictor. The devices are also evaluated in an R134a vapor compression system of 1.5-2 kW, with the ability to control mass flow that is found to be greatly influenced by the vapor compression cycle's operational parameters. After the inlet pressure, the level of subcooling proved to be the most important parameter. For a cycle operating between 29 deg C and 4 deg C , saturation temperatures in the condenser and evaporator, respectively, actuation of the device reduced the refrigerant mass flow rate by 3.5% with 0.6
^o
C subcooling and up to 10.8 % with 5 deg C subcooling.