A shell-and-tube heat exchanger is to be constructed with 1 in. 12 gage steel tubes. The cold fluid flowing in the tubes, is water flowing at the rate of 18,000 kg/h and is to be heated from 35°C to 65°C. The hot shell side fluid is also water and flows at the rate of 12,800 kg/h, entering at 95°C. The tube water flows at an average velocity of 0.3 m/s and the overall heat transfer coefficient of the exchanger is known to be 1600 W/m² °C.

Determine,
a) The number of tubes per pass,