# HW3 group - ChE 381 Fall 2013 HW#3 due Group 1 Two streams...

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ChE 381 Fall 2013 HW #3 due 9/18/13 Group 1. Two streams of nitrogen are mixed in a steady-state process. The first inlet stream has a flowrate of 5.0 mol/s and is at 500K, 2.0 atm. The second inlet stream is at 1.0 mol/s, 400K, 0.5 atm. The product stream has a pressure of 1.0 atm and temperature T out . (a) The mixing device is well-insulated. What is the entropy generation rate of this process? (b) The mixing device is not well-insulated. Find the value of Q and T out needed to maintain the minimum entropy generation rate if T is 100, 200, 300, 400 and 500K. How do these two operating parameters (Q or T out ) change in response to T ? Explain, in complete sentences, why you think each of these two parameters have the observed relationship with T . You may assume ideal gas behavior, but do not assume that C p is constant. Hint: Q and T
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Unformatted text preview: out should both increase as T increases. 2. A vortex tube design with no supplied power or moving parts proposes to separate inlet air (10.0 bar, 25 C) into a stream of cold air (-10 C, 1.0 atm) and warm air (30 C, 1.0 atm). The warm air stream has a mass flowrate 5 times that of the cold air stream. Assume ideal gas operation, but do not assume that C p is constant. (a) Under which operating conditions (T ) can this design operate without violating the 2 nd Law of Thermodynamics? Hint: should be feasible at all T. (b) You should have found that the proposed design is economically feasible at all operating conditions. If the cold temperature is set at 10K and the operating temperature (T ) is fixed at 300K, what is the maximum possible hot temperature for a thermodynamically feasible design?...
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• Fall '13
• Jarboe
• Thermodynamics, 300K, entropy generation rate, 10.0 bar

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