PURPOSE: To permit dealing with a transient state by using specific relations in controlling a cooling end point temp. and cooling rates to desired values by controlling the injection rate of refrigerant from nozzles to materials to be cooled.
CONSTITUTION: The equationsI, II (W: refrigerant flow density m3, m2 sec., h: strip thickness mm, v: transfer speed m/min, le: effective cooling length, m, k1W K3: constants, α: the coefft. determined by nozzle shape, Ti, To: cooling start and end point temps. °C, Qτ: total refrigerant flow rate m3/sec, CR: cooling rate °C/ sec) are used for controlling the injection rates of refrigerant of multiple headers H11, H12W in the transfer direction of a strip 10. At the changing of strip thickness under operation at said le and Qτ, the ratio C1 is determined by the equation III (h, h' and Qτ' Qτ' are the values before and after the change), and the injection rates of refrigerant are successively corrected. When the transfer speed changes during the same operation, the Qτ is changed simultaneously by the equation II, and when the le change exceeds the permissible range, it is changed so as to enter the range, and the Qτ by the change thereof is corrected. This correction is applied upon each nozzle when the imaginary change point showing the strip 10 boundary for presence or absence of the le change passes each nozzle.
TAKASHIMA TOSHIMASA
YUI KATSUHIKO
