6 Heat Transfer from a Hot Drawn Bar

A hot drawn bar, assumed to be moving at a constant velocity out of a die at constant temperature, will be treated as a one-dimensional heat transfer problem. The Biot numberfor the bar, h_tD∕2k, will be assumed to be less than 0.1, to assure no radial variation of temperature in the bar. Here h_t is the total heat transfer coefficient from the bar surface in W∕m²-K, the sum of the convection heat transfer coefficient and radiation heat transfer coefficient, D is the bar diameter, and k is the bar thermal conductivity in W∕m-K. Conduction, convection, and radiation heat transfer mechanisms affect the temperature of the drawn bar.