Patent ID: 7171815

Claim:
A method for operating a cryogenic tunnel through which products to be chilled or deep-frozen pass, which tunnel is equipped with means for injecting a cryogenic fluid as well as means for extracting, at a variable rate, some of the cold gases resulting from the vaporization of said fluid in the tunnel, wherein: a) obtaining a gas temperature, wherein said gas temperature comprises a value selected from the group consisting of the temperature of the gases in proximity to the entry to the tunnel, and the temperature of the gases in proximity to the exit to the tunnel, wherein said gas temperature is obtained from at least one gas temperature probe which is provided outside the tunnel, at a location selected from the group consisting of proximity to the tunnel entrance, and proximity to the tunnel exit; b) obtaining an ambient temperature, wherein said ambient temperature is obtained from at least one ambient temperature probe which is provided outside the tunnel; c) determining a first delta, wherein said first delta is the difference between said ambient temperature and said gas temperature; d) comparing the value of said first delta with a first setpoint value; and, e) controlling the extraction rate of said extraction means by feedback as a function of the result of the comparison in step d), in order to restore the value of said first delta to said setpoint value if necessary.