A steel strip emerges from the hot roll section of a steel mill at a speed of 20 m/s and a temperature of 1200 K. Its length and thickness are L = 100 m and 8 = 0.003 m. respectively, and its density and specific heat are 7900 kg/m 3 and 640 J/kg' K, respectively.

Accounting for heat transfer from the top and bottom surfaces and neglecting radiation and strip conduction effects, determine the time rate of change of the strip temperature at a distance of 1 m from the leading edge and at the trailing edge. Determine the distance from the leading edge at which the minimum cooling rate is achieved.

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Atmospheric air, T= 300 K Steel strip (1200 K) V= 20 ms Atmospheric air, T = 300 K