Unsteady HT Example
A 2-m long 0.2-m-diameter steel cylinder (k=40 W/m.K, a=1?10-5 m2/s, r=7854 kg/m3, c=434 J/kg.K), initially at 400 C, is suddenly immersed in water at 50 C for quenching process. If the convection coefficient is 200 W/m2.K, calculate after 20 minutes: (a) the center temperature, (b) the surface temperature, (c ) the heat transfer to the water.
- L/D=2/0.2=10, assume infinitely long cylinder
- Check Lumped Capacitance Method (LCM) assumption: Bi=h(ro/2)/k=(200)(0.1)/2/40=0.25ɬ.1, can not use LCM, instead use Heisler charts.