Chapter 12 Heat exchangers (Material presented in this chapter are based on those in Chapter 11, �Fundamentals of Heat and Mass Transfer�, Fifth Edition by Incropera and DeWitt) Heat exchanger is a device for heat exchange between two fluids, say hot and cold fluids. It is the workhorse of chemical, petrochemical, biochemical and power industries. Efficient energy transfer is an important aspect of power management in any industry. Therefore design of heat exchangers which facilitate energy transfer is very important. In this chapter, the functioning and characterization of heat exchangers and methods to assess their performance.
12.1
Classifications
Heat exchangers (HEs) are typically of two types based on the contact method, viz. direct contact HEs and two-phase HEs. Direct contact heat exchangers typically consists of wall between tubes, plates etc. This type of heat exchanger that has a wall between the two fluids is called transsmural heat oexchange. Two-phase heat exchangers are those in which two-phases are involved. Heat exchangers are classified based on the (geometrical) construction or flow arrangement. For instance heat exchangers can be concentric pipe heat exchangers, cross-flow heat exchangers, shell-tube heat exchangers. In all these cases, the hot and the cold may flow co-currently, that is, parallel-flow or counter-currently. Many different forms of shell-and-tube HEs may be possible, for example HE exchanger may involve multiple shell passes and 165