Experimental and numerical study of gas jet cooling at high Reynolds number

In order to achieve the necessary strip cooling rates for today’s high strength steels, values as high as 110-120°C/sec are needed to obtain the necessary temperature drop, typically between 800 and 250°C. This requires removal of about 350KW/m2 per side of the strip. For galvanised strip which cannot be quenched by water for surface quality reasons, specific gases are used. This requires a very high heat transfer coefficient in the range of 650 to 750KW/m2²depending on the temperature of the gas used. Laboratory experiments with air and computer modelling are described.