Figure 1: Schematic diagram of the vacuum cooler: (1) vacuum chamber; (2) infrared window fixed at the top of vacuum chamber; (3) online infrared thermal imager; (4) electromagnetic bleeding valve; (5) pressure sensor; (6) computer; (7) temperature sensor; (8) programmable logic controller; (9) frequency converter; (10) vacuum pump; (11) cold trap; (12) sample; and (13) standard temperature sensor used to real-timely calibrate the infrared thermal imaging equipment.