Water enters a small copper tube, with an inner diameter of 2.5 cm, at the rate of 0.025 kg/s and a temperature of 15°C. Steam is condensing on the outer surface of the tube at atmospheric pressure so that tube-surface temperature is uniformly at 100°C. If the tube length is 5 meters, determine (a) the outlet temperature, and (b) the average convection heat transfer coefficient between the water and the pipe.

Question

GIVEN
• Diameter of copper tube (Di)= 2.5 cm = 0.025 m
• Cooling water inlet temperature (Tin)= 200C
• Cooling water flow rate ( m• )=0.025 kg/s
• Tube length (L)= 5 m
• Surface temperature(Ts)=1000C
FIND (a) Outlet temperature
(b) Average convection heat transfer coefficient between water and pipe.
PROPERTIES AND CONSTANTS
for Water at 35°C: (guess bulk temperature)
Density (?) = 994.1 kg/m3
Specific heat (cp) = 4175 J/(kg K)
Thermal conductivity (k) = 0.624 W/(m K) A
bsolute viscosity (?) = 719.8 × 10–6 (Ns)/m2
Prandtl Number (Pr) = 4.8

Answer 1

Thus the flowrate is in laminar region.



Thus the average heat transfer coefficient between water and pipe is 760.6 W/(m2 K).

The rate of heat transfer to the cooling water is given by



Thus the cooling water outlet temperature is 95.40C.