# pset_7 - 180°C(we will presume that T 10 is not disturbed...

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Fall 2004 ICE Topics: Process Control by Design 10.492 Problem Set 7: alternative HX network base case For this problem set, work with one or two names will be accepted. Consider alternative heat exchanger networks: bypass W 1 T 6 T 5 T 4 T 1 T 9 T 7 E101 E102 E103 φ W 3 T 7a 1 1 9 7 E101 E102 E103 3 7a T 8 W 2 T 2 W 3 T 3 2 trim HX W 1 T 6 T 5 T 4 T 1 T 9 T 7 E101 E102 E103 T 7a E104 T 11 W u T 10 1 1 9 7 E101 E102 E103 7a E104 11 u 10 T 8 W 2 T 2 W 3 T 3 2 For each of these networks, (1) assemble the nonlinear equations that describe their steady-state behavior (2) classify the variables – there will now be 3 CV and 3 MV (3) determine the unknown reference values for the following specifications all heat capacities 2500 J kg -1 K -1 all heat transfer coefficients 250 W m -2 K -1 (inputs) W 1r : 8.2 kg s -1 T 1r :250°C T 2r :136°C T 3r :100°C T 10
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Unformatted text preview: : 180°C (we will presume that T 10 is not disturbed from this value) (outputs) T 6r : 129.3°C T 8r : 223.4°C T 9r : 168.8°C Step (3) constitutes your design, in which the result will be heat exchanger sizes and the bypass fraction to achieve the specified outputs, for the specified inputs. Are these enough specifications to determine a unique design? Recall that the original network used three exchangers of area 117 m 2 ; any or all of these may change for the new designs. Furthermore, the manipulated variables may assume new reference values. revised 2004 Nov 30 Dr. Barry S. Johnston, Copyright 2004. 1...
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