| 摘要 |
A controlled stream of liquid cryogen is delivered from a system comprising: a) a source of liquid cryogen at a substantially constant pressure, remote from the outlet; b) a conduit connecting the liquid cryogen source to the outlet; c) means to maintain cryogen flowing through the conduit sub-cooled at all points along the conduit (i.e., at any given point in the conduit, the cryogen's equilibrium vapor pressure is below the pressure experienced at that point in the conduit), and to deliver the cryogen to the outlet at a temperature equal to or below its boiling point at atmospheric pressure; and d) a flow-rate control restriction, positioned in the conduit. By maintaining the cryogen sub-cooled, the flow is kept substantially (at least about 95% by volume) liquid. Therefore, the flow in the conduit is controlled reliably as to pressure, flow rate, and size. Specifically, the rate at which liquid cryogen is delivered at the outlet is controlled by the cross-sectional area of the flow-control restriction, and severe flashing at the outlet is avoided. |
