US Patent 7987681 Refrigerant fluid flow control device and method

A subcool flow control valve useful in a refrigerant system includes an enclosure having a fluid flow pathway for a controlled fluid between an inlet and an outlet. A thermally conductive flexible wall forms a sealed cavity within the enclosure for carrying a controlling fluid. A metering orifice operable between the pathway and the outlet port controls an amount of metered fluid passing through the outlet port in response to movement of the flexible wall toward and away from the metering orifice in response to temperature changes of the controlled fluid transmitting temperature and thus pressure changes to the controlling fluid in the sealed cavity. Inverse thermal feedback means is formed as part of the valve for stabilizing valve operation thus providing means for transmitting a thermal signal from the metered controlled fluid back to the controlling fluid.