COURSE: CH2043 - HEAT TRANSFER PROCESSES AND EQUIPMENT
SEMESTER : SEPTEMBER 2023
TOPIC: CONVECTION HEAT TRANSFER
ASSIGNMENT 2
1. In a process plant, a steam pipe of 10-cm-diameter and 20-m long pipe is
exposed to ambient temperature of 5°C. The average temperature of the outer
surface of the steam pipe is 75°C and there are also light winds in the area at
10 km/h. The emissivity of the outer surface of the pipe is 0.8 and the average
temperature of the surfaces surrounding the pipe including the sky is estimated
to be 0°C.
a. Determine the amount of heat lost from the steam during a 10-h long
work day in the light winds condition.
[ 30 marks ]
b. Reconsider the problem if there is no wind in the area. Determine the
rate of heat lost from the pipe by natural convection during the 10-h
period. Compare the results obtained in part (a) and (b).
[ 30 marks ]
2. Oil at 15°C is to be heated by saturated steam at 1 atm in a double pipe heat
exchanger to a temperature of 25°C. The inner tube has a diameter of 3 cm and
the outer shell has a diameter of 5 cm. The oil enters the tube with a mass flow
rate of 0.8 kg/s and the inner tube may be assumed to be isothermal at 100°C,
and the outer tube is well insulated. Assuming full developed flow for oil,
determine the length required to heat the oil to the indicated temperature. In
reality you need a shorter or longer tube? Explain the answer.
[ 40 marks ]