A typical procedure for sizing a shell-and-tube heat exchanger with multiple tubes (single pass) is as follows:
a. Compute the heat load using Eq. (3.5.1) assuming countercurrent flow.
b. Use a chart provided for that type of exchanger to determine the correction factor F for the heat transfer, and multiply the log-mean temperature difference by this correction factor to estimate the actual exchanger performance
An example of such a chart is subsequently reproduced from the Chemical Engineers’ Handbook (1997, Section 10) in Figure P3.4. To use these charts, the following dimensionless temperature differences must be calculated:
A process stream having the properties of water on the tube side (stream 1) must be cooled from 80 to 50 ◦C at a flow rate of 100 L/min. Utility water is available at 5 ◦C and must be returned no hotter than 40 ◦C. You may assume the heat transfer coefficient is 1000 W/m2
K.
a. Determine the minimum flow rate and area of a plug–plug countercurrent heat exchanger required for accomplishing this task.
b. Using the chart provided, determine the minimal flow rate and area for a shell-andtube heat exchanger required for performing the same task.
c. If the shell side flow is such that the shell side is well mixed and the tube side (process stream) is plug flow, reanalyze the shell-and-tube heat exchanger as if it were a plug–mixed continuous-flow heat exchanger. Compare with the preceding part b and comment.