Three stirred-tanks in series are used in a reactor train (see Fig. E3.20). The flow rate into the system of some inert species is maintained constant while tracer test are conducted. Assuming that mixing in each tank is perfect and volumes are constant: (a) Derive model expressions for the concentration of tracer leaving each tank, c; is the concentration of tracer entering the first tank. (b) If c; has been constant and equal to zero for a long time and an operator suddenly injects a large amount of tracer material in the inlet to tank 1, what will be the form of c3(t) (i.e., what kind of time functions will be involved) if 1. v1 =V2 = V3 2. v1 ,e V2 ,e v3. (c) If the amount of tracer injected is unknown, is it possible to back-calculate the amount from experimental data? How?
ChE 20500 Hour Exam 3: Fall 2015, December 1, 2015 (8:00p – 9:30p) Instructions: Please complete the following problems on separate, numbered pages. Start each problem on a new page and write only on one side of a piece of paper. Only one side of a piece of paper will be graded. Circle your answer. Do not forget to show all work and state all assumptions that you make. Remember that an answer is not complete without a properly labeled process flow diagram. Problem 1. (50 points total) A liquid stream containing 50% pentane (C H ) and t5e 12lance hexane (C H ), on a molar 6as14, at T = 80 °C and P = 5 atmospheres is fed to a continuous flash evaporator. When the feed is exposed to the reduced pressure (P = 1.52 atm) in the evaporator, a substantial amount is vaporized. The temperature