The invention provides a negative-pressure
liquid nitrogen subcooler and a method therefore for reducing
liquid nitrogen temperature. The negative-pressure
liquid nitrogen subcooler comprises a liquid
nitrogen conveying
system, a subcooler
system, a negative-pressure air exhausting
system and a discharging system, wherein the liquid
nitrogen conveying system is used for supplying liquid
nitrogen to the subcooler system; the negative-pressure air exhausting system is used for reducing pressure for the subcooler; and the discharging system is used for discharging gasified nitrogen. In the negative-pressure liquid nitrogen subcooler, an electric heater is adopted to raise the temperature of
gaseous nitrogen to 20-30 DEG C, so that the subcooler is not limited to the weathers; a
liquid level sensor is adopted to automatically regulating the opening of a pneumatic regulating valve, so that the height of the liquid level is maintained. The method comprises the steps of: firstly, injecting the liquid nitrogen for a
liquid nitrogen container and regulating pressure; then injecting the liquid nitrogen for the subcooler, wherein the height of the liquid level of the liquid nitrogen in the subcooler is kept constant; then starting the negative-pressure air exhausting system, and cooling the liquid nitrogen through a
heat exchanger; and finally, recovering the liquid nitrogen and discharging the liquid nitrogen. According to the invention, the temperature of a
heat sink can be further reduced, the temperature of the
heat sink is regulatable within a range of 70-77k, and the advantagesof simple equipment, good effect and low
operating cost are achieved.