Page 240 - Modelling in Transport Phenomena A Conceptual Approach

220 CHAPTER 7. UNSTEADY-STATE MACROSCOPIC BALANCES

SUGGESTED FtEFEFtENCES FOR FURTHER
STUDY

Bird, R.B., W.C. Stewart and E.N. Lightfoot, 1960, Transport Phenomena, Wiley,
New York.

Churchill, S.W., 1974, The Interpretation and Use of Rate Data: The Rate
Concept, Scripta Publishing Co., Washington, D.C.

Felder, R.M. and R.W. Rousseau, 2000, Elementary Principles of Chemical
Processes, 3'd Ed., Wiley, New York.

Incropera, F.P. and D.P. DeWitt, 1996, Fundamentals of Heat and Mass Transfer,
4th Ed., Wiley, New York.

Whitwell, J.C. and R.K. Toner, 1969, Conservation of Mass and Energy, McGraw-
Hill, New York.

PROBLEMS

7.1 Two perfectly stirred tanks with capacities of 1.5 and 0.75m3 are connected
in such a way that the effluent from the first passes to the second. Both tanks are
initially filled with salt solution of 0.5 kg/L in concentration. If pure water is fed
to the first tank at a rate of 75 L/min, determine the salt concentration in the
second tank after 10 minutes?
(Answer: 0.423 kg/L)

7.2 Two vertical tanks placed on a platform are connected by a horizontal pipe
5 cm in diameter as shown in Figure 7.4. Each tank is 2 m deep and 1 m in diameter.
At first, the valve on the pipe is closed and one tank is full while the other one is
empty. When the valve is opened, the average velocity through the pipe is given
bY
(u) = 26
where (v) is the average velocity in m/ s and h is the difference between the levels
in the two tanks in meter. Calculate the time for the levels in the two tanks to
become equal.