Mercury flows through a pipe (316 Stainless Steel) with outside diameter of 0.02
ID: 1863337 • Letter: M
Question
Mercury flows through a pipe (316 Stainless Steel) with outside diameter of 0.0254 m (1 inch) and inside diameter of 0.01905 m (0.75 inch) at a rate of 2 kg/s. A cross flow of coolant with a temperature of 293 K cools the mercury from 800 K to 500 K. Ignoring natural convection and radiation determine the velocity of air that is required to cool the mercury. The thermal resistance from the liquid Mercury to the wall can be ignored.
Explanation / Answer
heat supplied by mercury = heat gained by cold air
heat suppleied by mercury = 2*.14*1000*(800-500) = 84000 J
heat gained by air = mass flow rate of air*specific heat capacity of air*(500-293)
= Velocity*area*denstiy of air*1020*(500-293)
= Velocity*3.14*1*0.0254*1.225*1020*(500-293)
hence velocity of air = 84000/20628.6 = 4.07 m/s