10.302 Fall 2004 Homework Problem Set 8 Due Wednesday, November 17, at start of classPart A1.Problem 11.38(a) of I&D What tube area would be required if the exchanger were of the true countercurrent type? 2. A mixed organic liquid is to be vaporized in a true countercurrent exchanger. The mixture will enter at 100°C and it is desired that it leave at 300°C. A temperature-enthalpy diagram is attached. As indicated, the design heat duty for the exchanger is 1 MW. A high temperature liquid heating medium will be used to achieve the vaporization. This fluid has a constant heat capacity equal to 2000 J/kg⋅K. (a)If the heating fluid enters the exchanger at 320°C, and if the exchanger is infinitely large, what is the required flow rate of the heating medium? (b)If the heating fluid enters the exchanger at 320°C, and if the exchanger is infinitely large, and if the flow rate of the heating medium is 2 kg/s, what will be the exit temperature or the mixed organic stream? Note that the actual heat duty maybe less than the desired value of 1 MW. (c)If the flow rate of the heating fluid (which enters at 320°C) is 3 kg/s and if the overall heat transfer coefficient is constant at 350 W/m2⋅K, what area will be required?
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