Using a negative step tracer input, Cholette and Cloutier (Can. J. Chem. Eng., 37, 107 (1959)) studied the RTD in a tank for different stirring speeds. Their tank had a 30-in. diameter and a fluid depth of 30 in. indide the tank. The inlet and exit flow rates were 1.15 gal/min. Here are some of their tracer results for the relative concentration, C/C0 (courtesy of the Canadian Society for Chemical Engineering):
NEGATIVE STEPS TRACER TEST

The CSTR tank with a stirrer that rotates counter-clockwise is shown. The negative step tracer input with flow rate v Subscript 0 is fed to the CSTR tank. The outlet from the tank has a resultant flow rate of v Subscript 0. The yardstick used in measuring is also shown. Calculate and plot the cumulative exit-age distribution, the intensity function, and the internal-age distributions as a function of time for this stirred tank at the two impeller speeds. Can you tell anything about the dead zones and bypassing at the different stirrer rates?

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Time (min) 170 10 15 20 25 30 Impeller Speed (rpm) 35 0.761 0.695 0.592 10 0.653 0.639 0.513 0.502 0.566 0.454 0.543 0.409 0.369