Chapter 7
HEAT EXCHANGERS
OBJECTIVES
After studying this chapter, the student will be able to:
▪ Describe the basic principles of fluid flow inside a heat exchanger.
▪ Explain the methods of heat transfer that apply to heat exchangers.
▪ Compare the operation of finned and plain tubes.
▪ List the basic parts of a hairpin (double-pipe) heat exchanger.
▪ Describe a shell and tube, fixed head, single-pass heat exchanger.
▪ Describe a shell and tube, fixed head, multi-pass pass heat exchanger.
CHAPTER 7 REVIEW QUESTIONS
1. List the methods of heat transfer. Discuss the interrelationships that exist between them
and how each applies to heat exchangers. Which is (are) the most critical and why?
Answer: The methods of heat transfer include conduction, convection and radiant heat
transfer. A combination of conduction and convection heat transfer processes can be
found in all heat exchangers. Both methods of heat transfer are equally important.
Radiant heat transfer does not take place in most heat exchanger systems.
When heat energy is transferred through a solid object it is referred to as
conduction. The molecules of the metal pick up heat energy and begin to vibrate quickly,
transferring heat energy from the hot side of the metal to the cooler side. As the hot
2. Draw and label a hairpin heat exchanger. Answer: See figure in chapter.
3. Draw and label a shell and tube heat exchanger. Answer: See figure in chapter.
4. Draw and label a kettle reboiler. Explain what is happening inside the device. Answer:
See figure in textbook. The liquid level is carefully controlled inside the shell of the
5. Describe laminar and turbulent flow. Answer: Two major classifications of fluid flow are
laminar and turbulent. Laminar flow or streamline flow moves through a system in thin
6. List five types of heat exchangers. Answer:
a. double-pipe
b. thermosiphon reboiler
7. What is meant by the term floating head? Answer: In a floating head, multi-pass heat
exchanger flow enters the channel head and is directed into the tubes. The tubes are U-
8. How are heaters, condensers, and reboilers related to distillation systems? Answer: Heat
exchangers can be used to heat or cool a process stream. Overhead condensers on
9. Contrast parallel and series flow through a heat exchanger. Answer: Heat exchangers can
be connected to cooling towers in a variety of ways. the two most common are series and
10. Draw an air-cooled heat exchanger. Answer: See the figure in the text.
11. Explain the purpose of using finned tubes in heat exchangers. Answer: Finned tubes
12. Describe the operation of a spiral heat exchanger. Answer: See the figure in the text. A
13. Draw and label a plate and frame heat exchanger. Answer: See the figure in the text.
14. Heat exchangers and cooling towers often team up to form industrial cooling systems.
Please explain this statement. Answer: Cool water is pumped from the cooling tower to
15. Does steam flow from top to bottom or from bottom to top inside a heat exchanger?
Please explain your answer. Answer: Steam enters at the top, cools, partially condenses,