# The relationship between design parameters and entropy generated in a heat exchanger is defined by..

The relationship between design parameters and entropy

generated in a heat exchanger is defined by Eq. (11.33). This relationship is

the subject of Problem 11.11. Show that the operating point corresponding to

equal outlet temperatures must correspond to maximum entropy generation. Assume

that the temperature effectiveness increases monotonically with NTU. Calculate

the number of transfer units that correspond to the maximum entropy generation

operating point for a counterflow exchanger with C* = 1.

A two-fluid heat exchanger of an arbitrary flow arrangement

has a specified number of

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The relationship between design parameters and entropy

generated in a heat exchanger is defined by Eq. (11.33). This relationship is

the subject of Problem 11.11. Show that the operating point corresponding to

equal outlet temperatures must correspond to maximum entropy generation. Assume

that the temperature effectiveness increases monotonically with NTU. Calculate

the number of transfer units that correspond to the maximum entropy generation

operating point for a counterflow exchanger with C* = 1.

A two-fluid heat exchanger of an arbitrary flow arrangement

has a specified number of transfer units NTU, and the heat capacity rate ratio

C*. The inlet temperatures of both fluids are known and their ratio is # ¼ T1;i/T2;i.

Derive the relationship between the entropy generated in this exchanger and its

design parameters as given by Eq. (11.33), in which the pressure drops are

neglected. Subsequently, calculate the entropy generation for a counterflow

heat exchanger having C* = 1 and an inlet temperature ratio of 0.5. Perform the

calculations for NTU = 1, 5, and 10 and discuss the change in entropy

generation with increased heat exchanger size. Finally, show how Eq. (11.28)

would change if there is finite pressure drop.

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