Question

A long, hot AISI 304 stainless steel bar of rectangular cross section has dimensions w = 3 mm, W = 5 mm, and L = 100 mm. The bar is exposed to air that provides a heat transfer coefficient of h = 15 W/m2 · K at all exposed surfaces and air temperature is 300K.

1. Determine an appropriate characteristic length Lc and the corresponding Biot number Bi that is associated with the transient thermal response of the solid object. State whether the lumped capacitance approximation is valid.

2. The initial temperature of the steel bar is 1100K. Calculate the time required for the bar to cool at 400K in air.

Answer 1