Mercury flows inside a copper tube 9 m long with a 5.1 cm inside diameter at an average velocity of 7 m/s. The temperature at the inside surface of the tube is 38°C uniformly throughout the tube, and the arithmetic mean bulk temperature of the mercury is 66°C. Assuming the velocity and temperature profiles are fully developed, calculate the rate of heat transfer by convection for the 9 m length by considering the mercury as

(a) An ordinary liquid and

(b) Liquid metal. Compare the results.

GIVEN

Mercury flows inside a copper tube

Tube length (L) = 9 m

Inside diameter (D) = 5.1 cm = 0.051 m

Average mercury velocity (V) = 7 m/s

Tube inside surface temperature (Ts) = 38°C (uniform)

Bulk temperature of mercury (Tb) = 66°C

ASSUMPTIONS

Steady state

Fully developed flow

D-5.1 cm Mercury V-7 m/s - 66C L= 9 m