The document defines key terms related to heat transfer and fluid flow, including thermal entrance region, hydrodynamic entrance region, fully developed flow, and log mean temperature difference. Equations are provided for calculating the log mean temperature difference. Diagrams of parallel flow and counterflow heat exchangers are referenced from Figure 11.1 of the textbook.

1. Homework 8 – Problem 1
A. Define the following terms: (use symbols and equations if necessary)
a. Thermal entrance region
b. Hydrodynamic entrance region
c. Fully developed flow
d. Log mean temperature difference
B. Draw a simple diagram of each of the following types of concentric heat exchangers
(Chapter 11)
H. Parallel flow
I. Counterflow
A. Define the following terms: (use symbols and equations if necessary)
a. Thermal entrance region
For laminar flow:
For turbulent flow on the other hand, the entry region is approximated by Nusselt
number correlations in Section 8.4.2.
b. Hydrodynamic entrance region
For laminar flow:
and for turbulent flow:
c. Fully developed flow
Once a flow is characterized as ‘fully developed’ (and remains that way), the
thermal and physical properties seize changing. This includes density and even
the convective heat transfer coefficient.
d. Log mean temperature difference
For external flow (bank of tubes): (i=in, o=out)
For heat exchangers: (h=hot, c=cold, i=in, o=out)
B. See Figure 11.1

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