主权项 |
1. A cold gas supply system for use with a liquid nitrogen bath, the liquid nitrogen bath having vapor therefrom, the system comprising:
a first pre-cooling coil for cooling a first pressurized gas stream by heat exchange with the vapor from the liquid nitrogen bath, said first pressurized gas stream comprised substantially of nitrogen, said bath contained in a cryostat having liquid capacity greater than 10 liters and less than 300 liters, the cryostat having a top, a condensing coil immersed in said bath to substantially condense said first pressurized gas stream to produce a pressurized liquid nitrogen stream, a second pre-cooling coil for cooling a second pressurized gas stream by heat exchange with the vapor from said bath to produce a pre-cooled second pressurized gas stream, said second pressurized gas stream comprised of nitrogen and helium of any ratio, a secondary cooling coil immersed in said bath to further cool said second pre-cooled second pressurized gas stream to produce a chilled gas stream, the chilled gas stream having a saturated vapor temperature, a first vacuum-insulated line for conveying the pre-cooled second pressurized gas stream from said second pre-cooling coil to said secondary cooling coil, a second vacuum-insulated line for conveying the chilled gas stream from said secondary cooling coil upward toward the top of said cryostat, a duct that injects said pressurized liquid nitrogen stream into said chilled gas stream, said secondary cooling coil further characterized as having heat transfer rate less than needed to cool said chilled gas stream below its saturated vapor temperature. |