In a shell-and-tube heat exchanger consisting of 1-in. schedule 40 steel pipe, 10,000 standard cubic feet per minute of air is to be heated from 1 atm and 70° to 205°P’ On the outside of the tubes, steam is condensing at 220°P’ A fan is available that will deliver cold air to the entrance header at 700P at a static pressure of 1.5 in. of water gauge. The hot air is to be discharged to the atmosphere. The cross-sectional areas of the entrance and exit headers are twice the total internal cross-sectional area of the tubes.
(a) Verify that the resistance on the steam side and the tube-wall conductive resistance are negligible.
(b) Calculate the number and length of each tube required.
(c) If the fan-motor combination has an efficiency of 0.39, what size motor is required?