EXTREMELY LOW-TEMPERATURE REFRIGERATING MACHINE

摘要

PROBLEM TO BE SOLVED: To execute a blocking elimination operation automatically at proper timing for eliminating the blocking in a heat exchanger in an extremely low- temperature refrigerating machine. SOLUTION: The extremely low-temperature refrigerating machine is provided with a differential pressure sensor (81) for detecting the difference between the pressure of inlet piping (77) in a high-pressure side channel (41) of a first heat exchanger (40) and the pressure of supply piping (70) located at the outlet side of the high-pressure side channel (41). When the detection value in the differential pressure sensor (81) is equal to or more than a specific criterion value, it is judged that the high-pressure side channel (41) has been blocked, and a helium gas at normal temperatures is supplied to the outlet side of the high-pressure side channel (41) through the supply piping (70). The helium gas flows back the high-pressure side channel (41), and discharges frozen objects adhering to the high-pressure side channel (41) to the suction side of the compressor.