https://processdesign.mccormick.northwestern.edu/index.php?title=Pinch_analysis&feed=atom&action=history
Pinch analysis - Revision history
2024-03-28T21:15:36Z
Revision history for this page on the wiki
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https://processdesign.mccormick.northwestern.edu/index.php?title=Pinch_analysis&diff=3030&oldid=prev
Mzuckerman at 05:53, 2 March 2015
2015-03-02T05:53:36Z
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 00:53, 2 March 2015</td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Computer tools for HEN design===</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Presently, the two previously described methods of pinch analysis are not in wide use in industry; rather analysis is performed by specialized software. These software include: Aspen HX-Net™ from Aspen Technology Inc., SUPERTARGET™ from Linnhoff March Ltd. and UniSim™ ExchangerNet™ from Honeywell International Inc. (Towler and Sinnott 2013). Stream data is often pulled directly from the process simulations by the software package. Automatically generated networks must be properly constrained lest an unfeasible amount of stream splits and loops be generated. There is great value, however, in the ability of software packages to perform many tweaks and iterations to fine tune a network.</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Presently, the two previously described methods of pinch analysis are not in wide use in industry; rather analysis is performed by specialized software. These software include: Aspen HX-Net™ from Aspen Technology Inc., SUPERTARGET™ from Linnhoff March Ltd. and UniSim™ ExchangerNet™ from Honeywell International Inc. (Towler and Sinnott 2013). Stream data is often pulled directly from the process simulations by the software package. Automatically generated networks must be properly constrained lest an unfeasible amount of stream splits and loops be generated. There is great value, however, in the ability of software packages to perform many tweaks and iterations to fine tune a network.</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>| hot</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>| 40.0</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>| 180</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>| hot</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The first step is to calculate the interval temperatures. Because the minimum approach temperature is 20°C, the interval temperatures for the hot stream are 10 °C less than the actual temperature and those for the cold stream are 10°C more than the actual temperature. The next step is to rank the interval temperatures, ignoring any duplicated values. We then determine what streams belong in which interval. The sum of CP values for the cold streams minus that for the hot streams can then be multiplied by the</div></td>
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<td class="diff-marker"><a class="mw-diff-movedpara-right" title="Paragraph was moved. Click to jump to old location." href="#movedpara_4_0_lhs">⚫</a></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><a name="movedpara_2_46_rhs"></a>[[File:<ins style="font-weight: bold; text-decoration: none;"> Problem table</ins> example.PNG|thumb|500px|center|<ins style="font-weight: bold; text-decoration: none;">Problem</ins> <ins style="font-weight: bold; text-decoration: none;">table</ins> <ins style="font-weight: bold; text-decoration: none;">exhibiting</ins> <ins style="font-weight: bold; text-decoration: none;">cascade</ins> <ins style="font-weight: bold; text-decoration: none;">taken</ins> from Figure 3.<ins style="font-weight: bold; text-decoration: none;">28</ins> of Towler and Sinnott]]</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The amount of heat added at the top to remove any negative values, 2900 kW, is the hot utility. The 600 kW left over at the bottom is the cold utility required. The pinch occurs where the heat transferred is zero, that is at interval number 4, interval temperature 90 °C. This is equivalent to 100°C in the hot stream or 80°C in the cold stream.</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Now we need to design the actual system:</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td class="diff-marker"><a class="mw-diff-movedpara-left" title="Paragraph was moved. Click to jump to new location." href="#movedpara_2_46_rhs">⚫</a></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><a name="movedpara_4_0_lhs"></a>[[File:<del style="font-weight: bold; text-decoration: none;">Pinch</del> example.PNG|thumb|500px|center|<del style="font-weight: bold; text-decoration: none;">Proposed</del> <del style="font-weight: bold; text-decoration: none;">Heat</del> <del style="font-weight: bold; text-decoration: none;">Exchanger</del> <del style="font-weight: bold; text-decoration: none;">Network for example</del> <del style="font-weight: bold; text-decoration: none;">problem</del> from Figure 3.<del style="font-weight: bold; text-decoration: none;">29</del> of Towler and Sinnott]]</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>'''Above Pinch'''</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>'''Above Pinch'''</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># CPh ≤ CPc</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># CPh ≤ CPc</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div># <del style="font-weight: bold; text-decoration: none;">We</del> <del style="font-weight: bold; text-decoration: none;">can</del> match stream 1 or 2 with stream 3 but neither stream can match with stream 4. This <del style="font-weight: bold; text-decoration: none;">creates</del> <del style="font-weight: bold; text-decoration: none;">a problem</del>, since if we match stream 1 with 3 then stream 2 will not be able to make a match at the pinch. Likewise, if we match stream 2 with 3 then stream 1 will not <del style="font-weight: bold; text-decoration: none;">be able to make</del> a match at the pinch.</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># <ins style="font-weight: bold; text-decoration: none;">It</ins> <ins style="font-weight: bold; text-decoration: none;">is possible to</ins> match stream 1 or 2 with stream 3 but neither stream can match with stream 4. This <ins style="font-weight: bold; text-decoration: none;">is</ins> <ins style="font-weight: bold; text-decoration: none;">problematic</ins>, since if we match stream 1 with 3 then stream 2 will not be able to make a match at the pinch. Likewise, if we match stream 2 with 3 then stream 1 will not <ins style="font-weight: bold; text-decoration: none;">have</ins> a match at the pinch.</div></td>
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<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># Check the heat available in bringing the hot streams to the pinch temperature.</div></td>
<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># Check the heat available in bringing the hot streams to the pinch temperature.</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#::stream 1 ΔH = 40.0(180 − 100 )= 3200 kW</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#::stream 1 ΔH = 40.0(180 − 100 )= 3200 kW</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#::ΔHcold = 2400 − 1800 = 600 kW</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>#::ΔHcold = 2400 − 1800 = 600 kW</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># Transfer the full heat load from stream 2 to second leg of stream 3; this satisfies both streams.</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># Transfer the full heat load from stream 2 to second leg of stream 3; this satisfies both streams.</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[File: Pinch example.PNG|thumb|500px|center|Proposed Heat Exchanger Network for example problem from Figure 3.29 of Towler and Sinnott]]</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==References==</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==References==</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Biegler LT, Grossmann IE, Westerberg AW. Systematic Methods of Chemical Process Design. Upper Saddle River: Prentice Hall; 1997. </div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Biegler LT, Grossmann IE, Westerberg AW. Systematic Methods of Chemical Process Design. Upper Saddle River: Prentice Hall; 1997. </div></td>
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Mzuckerman
https://processdesign.mccormick.northwestern.edu/index.php?title=Pinch_analysis&diff=2912&oldid=prev
Mzuckerman at 03:47, 2 March 2015
2015-03-02T03:47:29Z
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 22:47, 1 March 2015</td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Minimum approach temperature==</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Minimum approach temperature==</div></td>
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<td class="diff-marker" data-marker="−"></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The minimum approach temperature represents the smallest gap in temperature across which heat transfer will occur in the system. This often only occurs at the pinch. While technically any value greater than zero can allow for heat transfer, very small values are not often feasible. Low temperature differences decrease the need for additional utilities, but require increasingly large heat transfer areas, meaning larger heat exchangers. The trade-off between operating costs and capital costs should be used to choose the minimum approach temperature for the network. Typical choices for minimum approach temperatures are between 5 °C and 30 °C (Towler <del style="font-weight: bold; text-decoration: none;">128</del>). </div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The minimum approach temperature represents the smallest gap in temperature across which heat transfer will occur in the system. This often only occurs at the pinch. While technically any value greater than zero can allow for heat transfer, very small values are not often feasible. Low temperature differences decrease the need for additional utilities, but require increasingly large heat transfer areas, meaning larger heat exchangers. The trade-off between operating costs and capital costs should be used to choose the minimum approach temperature for the network. Typical choices for minimum approach temperatures are between 5 °C and 30 °C (Towler <ins style="font-weight: bold; text-decoration: none;">and Sinnott 2013</ins>). </div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>==Analysis Methods==</div></td>
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<td class="diff-marker"><a class="mw-diff-movedpara-left" title="Paragraph was moved. Click to jump to new location." href="#movedpara_6_0_rhs">⚫</a></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><a name="movedpara_3_0_lhs"></a>==Composite curves method==</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Pinch technology is a highly used and advanced technology throughout industry. Because of this, there have been devised multiple approaches with which to solve a pinch system. </div></td>
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<td class="diff-marker"><a class="mw-diff-movedpara-left" title="Paragraph was moved. Click to jump to new location." href="#movedpara_6_1_rhs">⚫</a></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><a name="movedpara_5_0_lhs"></a>[[File:Composite Curves example.png|thumb|<del style="font-weight: bold; text-decoration: none;">200px</del>|<del style="font-weight: bold; text-decoration: none;">right</del>|Example of composite curve method taken from Sieder Fig 10.7 ]]</div></td>
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<td colspan="2" class="diff-empty diff-side-deleted"></td>
<td class="diff-marker"><a class="mw-diff-movedpara-right" title="Paragraph was moved. Click to jump to old location." href="#movedpara_3_0_lhs">⚫</a></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><a name="movedpara_6_0_rhs"></a><ins style="font-weight: bold; text-decoration: none;">=</ins>==Composite curves method<ins style="font-weight: bold; text-decoration: none;">=</ins>==</div></td>
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<td class="diff-marker"><a class="mw-diff-movedpara-right" title="Paragraph was moved. Click to jump to old location." href="#movedpara_5_0_lhs">⚫</a></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><a name="movedpara_6_1_rhs"></a>[[File:Composite Curves example.png|thumb|<ins style="font-weight: bold; text-decoration: none;">600px</ins>|<ins style="font-weight: bold; text-decoration: none;">center</ins>|Example of composite curve method taken from Sieder<ins style="font-weight: bold; text-decoration: none;"> et al.</ins> Fig 10.7 ]]</div></td>
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<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>This method uses a graphical approach and makes obvious the presence and location of the pinch in the system. First one combines all hot streams into single composite curve on a temperature-enthalpy graph. The same is then done with the cold streams. Plotting both composite curves on a temperature-enthalpy plot reveals a pinch at the point where the cold and hot curves are closest in temperature. Because change in enthalpy is the feature of concern, the composite curves can be freely shifted along the enthalpy axis. In this manner the minimum approach temperature can be satisfied at the pinch.</div></td>
<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>This method uses a graphical approach and makes obvious the presence and location of the pinch in the system. First one combines all hot streams into single composite curve on a temperature-enthalpy graph. The same is then done with the cold streams. Plotting both composite curves on a temperature-enthalpy plot reveals a pinch at the point where the cold and hot curves are closest in temperature. Because change in enthalpy is the feature of concern, the composite curves can be freely shifted along the enthalpy axis. In this manner the minimum approach temperature can be satisfied at the pinch.</div></td>
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<td class="diff-marker" data-marker="−"></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>==Problem table method==</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">=</ins>==Problem table method<ins style="font-weight: bold; text-decoration: none;">=</ins>==</div></td>
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<td class="diff-marker" data-marker="−"></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The problem table method, also known as the cascade method, forgoes graphs for a numerical approach. This method is useful when solving heat-exchanger network problems manually, but has fallen into disuse due to the advent of modern computing. The first step in the process is converting stream temperatures into interval temperatures. To do this, one <del style="font-weight: bold; text-decoration: none;">sutracts</del> half the</div></td>
<td class="diff-marker" data-marker="+"></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The problem table method, also known as the cascade method, forgoes graphs for a numerical approach. This method is useful when solving heat-exchanger network problems manually, but has fallen into disuse due to the advent of modern computing. The first step in the process is converting stream temperatures into interval temperatures. To do this, one <ins style="font-weight: bold; text-decoration: none;">subtracts</ins> half the<ins style="font-weight: bold; text-decoration: none;"> minimum approach temperature from the hot stream temperatures, and adds half to the cold stream temperatures. The intervals are then ranked in order of magnitude, ignoring any repetitions. The next step involves balancing the heat carried by streams between each interval. Any excess heat cascades over into the next lower down interval. Add heat from the top of the system eliminate any negative values. The amount added at the top corresponds to hot utility duty, while the remaining value at the bottom corresponds to heat that must be removed by cold utility. </ins></div></td>
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<td class="diff-marker" data-marker="−"></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>minimum approach temperature from the hot stream temperatures, and adds half to the</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>cold stream temperatures. The intervals are then ranked in order of magnitude, ignoring any repetitions. The next step involves balancing the heat carried by streams between each interval. Any excess heat cascades over into the next lower down interval. Add heat from the top of the system eliminate any negative values. The amount added at the top corresponds to hot utility duty, while the remaining value at the bottom corresponds to heat that must be removed by cold utility. </div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:Cascade.PNG|thumb|500px|center|Example of the problem table method. The right most column contains both the minimum heating requirement for the system at the top, and the minimum cooling requirement at the bottom]]</div></td>
<td class="diff-marker"></td>
<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:Cascade.PNG|thumb|500px|center|Example of the problem table method. The right most column contains both the minimum heating requirement for the system at the top, and the minimum cooling requirement at the bottom]]</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>==Computer tools for HEN design==</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">=</ins>==Computer tools for HEN design<ins style="font-weight: bold; text-decoration: none;">=</ins>==</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Presently, pinch analysis is performed by specialized software <del style="font-weight: bold; text-decoration: none;">the</del> <del style="font-weight: bold; text-decoration: none;">majority</del> <del style="font-weight: bold; text-decoration: none;">of</del> <del style="font-weight: bold; text-decoration: none;">the</del> <del style="font-weight: bold; text-decoration: none;">time</del> <del style="font-weight: bold; text-decoration: none;">in</del> <del style="font-weight: bold; text-decoration: none;">industry</del>. Stream data is often pulled directly from the process simulations by the software package. Automatically generated networks must be properly constrained lest an unfeasible amount of stream splits and loops be generated. There is great value, however, in the ability of software packages to perform many tweaks and iterations to fine tune a network.</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Presently,<ins style="font-weight: bold; text-decoration: none;"> the two previously described methods of</ins> pinch<ins style="font-weight: bold; text-decoration: none;"> analysis are not in wide use in industry; rather</ins> analysis is performed by specialized software<ins style="font-weight: bold; text-decoration: none;">.</ins> <ins style="font-weight: bold; text-decoration: none;">These</ins> <ins style="font-weight: bold; text-decoration: none;">software</ins> <ins style="font-weight: bold; text-decoration: none;">include:</ins> <ins style="font-weight: bold; text-decoration: none;">Aspen</ins> <ins style="font-weight: bold; text-decoration: none;">HX-Net™</ins> <ins style="font-weight: bold; text-decoration: none;">from</ins> <ins style="font-weight: bold; text-decoration: none;">Aspen Technology Inc</ins>.<ins style="font-weight: bold; text-decoration: none;">, SUPERTARGET™ from Linnhoff March Ltd. and UniSim™ ExchangerNet™ from Honeywell International Inc. (Towler and Sinnott 2013). </ins> Stream data is often pulled directly from the process simulations by the software package. Automatically generated networks must be properly constrained lest an unfeasible amount of stream splits and loops be generated. There is great value, however, in the ability of software packages to perform many tweaks and iterations to fine tune a network.</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[File:Pinch example.PNG|thumb|500px|center|Proposed Heat Exchanger Network for example problem from Figure 3.29 of Towler and Sinnott]]</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>'''Above Pinch'''</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># CPh ≤ CPc</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># We can match stream 1 or 2 with stream 3 but neither stream can match with stream 4. This creates a problem, since if we match stream 1 with 3 then stream 2 will not be able to make a match at the pinch. Likewise, if we match stream 2 with 3 then stream 1 will not be able to make a match at the pinch.</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># Check the heat available in bringing the hot streams to the pinch temperature.</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#::stream 1 ΔH = 40.0(180 − 100 )= 3200 kW</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#::stream 2 ΔH = 30.0 (150 − 100 ) = 1500 kW</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># Check the heat required to bring the cold streams from the pinch temperature to their target temperatures.</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#::stream 3 ΔH = 60.0(180 – 80)= 6000 kW</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#::stream 4 ΔH = 20.0(160 – 80) = 1600 kW</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># If we split stream 3 into two branches with CP of 40.0 and 20.0, then we can match the larger branch with stream 1 and transfer 3200 kW, which satisfies (ticks off) stream 1.</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># We now have two cold streams, both with CP of 20.0, and one hot stream (2) with CP of 30.0. We need to split stream 2 into two branches. As an initial guess these can both have CP of 15.0. We can then match one branch of stream 2 with the smaller branch of 4 and transfer 750 kW, and the other branch with stream 3, also for 750 kW, which then ticks off stream 2.</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># Include a heater on the larger branch of stream 3 to bring it to its target temperature:</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#::ΔHhot = 40 (100 ) − 3200 = 800 kW</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># Include a heater on the smaller branch of stream 3 to provide the balance of the heat required:</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#::ΔHhot = 20 (100 ) – 750 = 1250 kW</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># Include a heater on stream 4 to provide the balance of the heat required:</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#::Δ Hhot = 1600 − 750 = 850 kW</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># Check sum of heater duties = 800 + 1250 + 850 = 2900 kW = hot utility target.</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>'''Below Pinch'''</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># CPh ≥ CPc</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># Note that stream 4 starts at the pinch temperature and so cannot provide any cooling below the pinch.</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># We cannot match stream 1 or 2 with stream 3 at the pinch.</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># Split stream 3 to reduce CP. An even split will allow both streams 1 and 2 to be matched with the split streams adjacent to the pinch, so try this initially.</div></td>
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<td class="diff-marker" data-marker="+"></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># Check the heat available from bringing the hot streams from the pinch temperature to their target temperatures:</div></td>
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<td class="diff-marker" data-marker="+"></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#::stream 1 ΔH = 40.0 (100 − 40 ) = 2400 kW</div></td>
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<td class="diff-marker" data-marker="+"></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#::stream 2 ΔH = 30.0 (100 − 60 ) = 1200 kW</div></td>
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<td class="diff-marker" data-marker="+"></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># Check the heat required to bring the cold streams from their source temperatures to the pinch temperature:</div></td>
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<td class="diff-marker" data-marker="+"></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#::stream 3 ΔH = 60.0 (80 − 30 ) = 3000 kW</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#::Stream 4 is at the pinch temperature</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># Note that stream 1 cannot be brought to its target temperature of 40 °C by full interchange with stream 3 as the source temperature of stream 3 is 30 °C, so ΔTmin would be violated. So transfer 1800 kW to one leg of the split stream 3.</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># Check temperature at exit of this exchanger:</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#::Temp out= 100 – 1800/40= 55 °C, satisfactory</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># Provide cooler on stream 1 to bring it to its target temperature; the cooling needed is</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>#::ΔHcold = 2400 − 1800 = 600 kW</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># Transfer the full heat load from stream 2 to second leg of stream 3; this satisfies both streams.</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==References==</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==References==</div></td>
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<td class="diff-marker"><a class="mw-diff-movedpara-right" title="Paragraph was moved. Click to jump to old location." href="#movedpara_20_0_lhs">⚫</a></td>
<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><a name="movedpara_16_0_rhs"></a><ins style="font-weight: bold; text-decoration: none;">Biegler</ins> <ins style="font-weight: bold; text-decoration: none;">LT</ins>, <ins style="font-weight: bold; text-decoration: none;">Grossmann</ins> <ins style="font-weight: bold; text-decoration: none;">IE</ins>, <ins style="font-weight: bold; text-decoration: none;">Westerberg AW</ins>. Systematic Methods of Chemical Process Design<ins style="font-weight: bold; text-decoration: none;">.</ins> Upper Saddle River<ins style="font-weight: bold; text-decoration: none;">: Prentice Hall;</ins> 1997.<ins style="font-weight: bold; text-decoration: none;"> </ins></div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>1. G.P. Towler, R. Sinnott, ''Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design'', Elsevier, 2012.</div></td>
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<td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Seider WD, Seader JD, Lewin DR. Process Design Principles: Synthesis, Analysis, and Evaluation. 3rd ed. New York: Wiley; 2004. </div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><a name="movedpara_20_0_lhs"></a><del style="font-weight: bold; text-decoration: none;">2.</del> <del style="font-weight: bold; text-decoration: none;">L.T. Biegler</del>, <del style="font-weight: bold; text-decoration: none;">I.E.</del> <del style="font-weight: bold; text-decoration: none;">Grossmann</del>, <del style="font-weight: bold; text-decoration: none;">A</del>.<del style="font-weight: bold; text-decoration: none;">W. Westerberg,</del> <del style="font-weight: bold; text-decoration: none;">''</del>Systematic Methods of Chemical Process Design<del style="font-weight: bold; text-decoration: none;">'', Prentice-Hall:</del> Upper Saddle River<del style="font-weight: bold; text-decoration: none;">,</del> 1997.</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">Towler</ins> <ins style="font-weight: bold; text-decoration: none;">G</ins>, <ins style="font-weight: bold; text-decoration: none;">Sinnott</ins> R. <ins style="font-weight: bold; text-decoration: none;">Chemical</ins> <ins style="font-weight: bold; text-decoration: none;">Engineering</ins> Design<ins style="font-weight: bold; text-decoration: none;">:</ins> Principles, <ins style="font-weight: bold; text-decoration: none;">Practice</ins> and <ins style="font-weight: bold; text-decoration: none;">Economics of Plant and</ins> <ins style="font-weight: bold; text-decoration: none;">Process Design. 2nd ed. Boston</ins>: <ins style="font-weight: bold; text-decoration: none;">Elsevier;</ins> <ins style="font-weight: bold; text-decoration: none;">2013.</ins> </div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del style="font-weight: bold; text-decoration: none;">4.</del> R<del style="font-weight: bold; text-decoration: none;">.T.</del> <del style="font-weight: bold; text-decoration: none;">Turton</del>, <del style="font-weight: bold; text-decoration: none;">R.C.</del> <del style="font-weight: bold; text-decoration: none;">Bailie</del>, <del style="font-weight: bold; text-decoration: none;">W.B.</del> <del style="font-weight: bold; text-decoration: none;">Whiting</del>, <del style="font-weight: bold; text-decoration: none;">J</del>.<del style="font-weight: bold; text-decoration: none;">A. Shaeiwitz,</del> <del style="font-weight: bold; text-decoration: none;">''</del>Analysis, Synthesis, and Design of Chemical Processes<del style="font-weight: bold; text-decoration: none;">'',</del> <del style="font-weight: bold; text-decoration: none;">Prentice</del> <del style="font-weight: bold; text-decoration: none;">Hall:</del> Upper Saddle River<del style="font-weight: bold; text-decoration: none;">,</del> <del style="font-weight: bold; text-decoration: none;">2003</del>.</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">Turton</ins> R<ins style="font-weight: bold; text-decoration: none;">,</ins> <ins style="font-weight: bold; text-decoration: none;">Bailie RC</ins>, <ins style="font-weight: bold; text-decoration: none;">Whiting</ins> <ins style="font-weight: bold; text-decoration: none;">WB</ins>, <ins style="font-weight: bold; text-decoration: none;">Shaewitz</ins> <ins style="font-weight: bold; text-decoration: none;">JA</ins>, <ins style="font-weight: bold; text-decoration: none;">Bhattacharyya D</ins>. Analysis, Synthesis, and Design of Chemical Processes<ins style="font-weight: bold; text-decoration: none;">.</ins> <ins style="font-weight: bold; text-decoration: none;">4th</ins> <ins style="font-weight: bold; text-decoration: none;">ed.</ins> Upper Saddle River<ins style="font-weight: bold; text-decoration: none;">: Prentice-Hall;</ins> <ins style="font-weight: bold; text-decoration: none;">2012</ins>.</div></td>
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Mzuckerman
https://processdesign.mccormick.northwestern.edu/index.php?title=Pinch_analysis&diff=2239&oldid=prev
Mzuckerman at 04:59, 7 February 2015
2015-02-07T04:59:55Z
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>==Introduction==</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Pinch analysis is a methodology used to minimize energy consumption of chemical processes by optimizing energy recovery methods. A pinch occurs at the closest point of approach between hot and cold streams in the network. By designing around this point energy from utilities can be minimized. This page focuses on pinch analysis in the context of heat exchanger networks (HENs), however similar methods can be used in the design of mass exchanger networks (MENs).</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>==Pinch technology==</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>For maximum energy recovery (MER), energy should not be transferred across the pinch. The network is separated into hot and cold regions, above and below the pinch respectively. In the hot region, streams are matched so that heat is transferred from the coolest possible source. Below the pinch, the opposite occurs. This yields the minimum utility requirement solution to the heat exchanger network.</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Minimum utility requirement is not necessarily the optimum solution, however, the solution with the lowest overall cost is. Minimizing the size and quantity of heat exchangers plays a large role in decreasing capital costs. There is a trade-off between operational and capital costs. In some cases transfer across the pinch is necessary to produce the optimal network. For more information see the trade-off section of the [[Sensitivity analysis and design optimization]] page. </div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><br /></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>==Minimum approach temperature==</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The minimum approach temperature represents the smallest gap in temperature across which heat transfer will occur in the system. This often only occurs at the pinch. While technically any value greater than zero can allow for heat transfer, very small values are not often feasible. Low temperature differences decrease the need for additional utilities, but require increasingly large heat transfer areas, meaning larger heat exchangers. The trade-off between operating costs and capital costs should be used to choose the minimum approach temperature for the network. Typical choices for minimum approach temperatures are between 5 °C and 30 °C (Towler 128). </div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>==Composite curves method==</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[File:Composite Curves example.png|thumb|200px|right|Example of composite curve method taken from Sieder Fig 10.7 ]]</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>This method uses a graphical approach and makes obvious the presence and location of the pinch in the system. First one combines all hot streams into single composite curve on a temperature-enthalpy graph. The same is then done with the cold streams. Plotting both composite curves on a temperature-enthalpy plot reveals a pinch at the point where the cold and hot curves are closest in temperature. Because change in enthalpy is the feature of concern, the composite curves can be freely shifted along the enthalpy axis. In this manner the minimum approach temperature can be satisfied at the pinch.</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>==Problem table method==</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The problem table method, also known as the cascade method, forgoes graphs for a numerical approach. This method is useful when solving heat-exchanger network problems manually, but has fallen into disuse due to the advent of modern computing. The first step in the process is converting stream temperatures into interval temperatures. To do this, one sutracts half the</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>cold stream temperatures. The intervals are then ranked in order of magnitude, ignoring any repetitions. The next step involves balancing the heat carried by streams between each interval. Any excess heat cascades over into the next lower down interval. Add heat from the top of the system eliminate any negative values. The amount added at the top corresponds to hot utility duty, while the remaining value at the bottom corresponds to heat that must be removed by cold utility. </div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[File:Cascade.PNG|thumb|500px|center|Example of the problem table method. The right most column contains both the minimum heating requirement for the system at the top, and the minimum cooling requirement at the bottom]]</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>==Computer tools for HEN design==</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Presently, pinch analysis is performed by specialized software the majority of the time in industry. Stream data is often pulled directly from the process simulations by the software package. Automatically generated networks must be properly constrained lest an unfeasible amount of stream splits and loops be generated. There is great value, however, in the ability of software packages to perform many tweaks and iterations to fine tune a network.</div></td>
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<td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>2. L.T. Biegler, I.E. Grossmann, A.W. Westerberg, ''Systematic Methods of Chemical Process Design'', Prentice-Hall: Upper Saddle River, 1997.</div></td>
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Mzuckerman
https://processdesign.mccormick.northwestern.edu/index.php?title=Pinch_analysis&diff=1854&oldid=prev
Jian: Created page with " <br> Author: Micah Zuckerman <sup> [2015] </sup> Stewards: Jian Gong and Fengqi You"
2015-01-26T20:04:04Z
<p>Created page with " <br> Author: Micah Zuckerman <sup> [2015] </sup> Stewards: Jian Gong and Fengqi You"</p>
<p><b>New page</b></p><div><br />
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Author: Micah Zuckerman <sup> [2015] </sup><br />
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Stewards: Jian Gong and Fengqi You</div>
Jian