Heat water by condensing steam in the shell. The flow rate of the water is 15 kg/s and it is heated from 60 to 80°C. The steam condenses at 140°C and the overall heat transfer coefficient of the heat exchanger is 820 W/(m² K). If there are 45 tubes with an OD of 2.75 cm, calculate the length of tubes required.

GIVEN

• Shell-and-tube heat exchanger with two tube passes and one shell pass
• Water in tubes, condensing steam in shell
• Water flow rate (m_w ) = 15 kg/s
• Water temperatures
• T_w,in = 60°C
• T_w,out = 80°C
• Steam temperature (T_s) = 140°C
• Overall heat transfer coefficient (U) = 820 W/(m² K)
• Number of tubes (N) = 45
• Tube outside diameter (D) = 2.75 cm = 0.0275 m

ASSUMPTIONS

• Counterflow

Tout-80C Steam Te- 140C