Delta T log mean - Heat Exchanger - Mid Term Exam - W8Q1

A condensing steam at a temperature of 130oC is used to heat water flowing counterly through a heat exchanger at 1.4 kg/s from 30oC to 80oC. The water is flowing through a thin walled pipe of 100 mm in diameter. Assuming that the specific heat capacity of water is constant and equal to 4180 J/(kg·K), Heat of vaporisation for water/steam at 130℃ is 2200 kJ/kg, and the overall heat transfer coefficient for the heat exchanger is 600 W/(m2·K).
a) What is the rate of heat transfer for the heat exchanger? (1 mark)
b) What mass flowrate of condensing steam is required? (1 mark)
c) What is the log mean temperature difference? (1 mark)
d) What area of heat exchanger would be required? (1 mark)
e) What length of pipe would be required? (1 mark)

Answers: a) 292.6 kW b) 0.133 kg/s c) 72.13 K d) 6.76 m² e) 21.5 m