Question

The condenser of a large steam power plant is a heat exchanger in which steam is condensed to liquid water. Assume the condenser to be a parallel flow shell-and-tube heat exchanger consisting of a single shell and 10,000 tubes, each executing two passes. The tubes are of thin wall construction with D = 30 mm and the steam condenses on their outer surface. The heat transfer rate that must be effected by the exchanger is Q = 2 × 10^9 W, and this is accomplished by passing cooling water through the tubes at a rate of 1×10^4 kg/s. The water enters at 20 ̊C, while the steam condenses at 90 C̊. The average velocity of steam on the tube surface is 10 m/s. use 50 C̊ as the bulk mean temperature for the water.

Assumption:

- Steam flow on the outer surface of the tube is assumed to be external forced flow.

- Water flow on the inner surface of the tube is assumed to be internal forced flow.

- Negligible heat transfer between heat exchanger and surroundings.

- Negligible kinetic and potential energy changes.

Get :

• Estimate the convective heat transfer coefficient between steam and the outer surface of the tube.
• Estimate the convective heat transfer coefficient between water and the inner surface of the tube.
• Estimate the overall heat transfer coefficient.
• What is the required tube length L per pass if LMTD method is used?

Answer 1