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Class 6

# Class 6 - 1 3 2 H H 2 4C 3 4 1 Heat Integration Heat...

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Heat Integration 1 1 H H 2 2 3 3 4 4 C

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Heat Exchanger Network Unknown Arrangement of Heat Exchangers Hot and cold streams never match ideally with respect to heat availability and temperature Need auxiliary utility network in addition to heat exchange network 1 s c T 2 s c T N 2 s c T 1 t c T 2 t c T N 2 t c T 1 s h T 2 s h T N 1 s h T 1 s h T 2 s h T N 1 s h T
Solar Plant – Process Flow Diagram

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Heat Exchanger Network Auxiliary coolers Auxiliary heaters Hot streams in Cold streams in Interior network These may not be required on all streams.
HEN Objectives Seek most economical network that meets stream specs Minimize utilities temperature-interval method composite curve method linear programming method Position heat exchangers stream matching at the pinch mixed-integer linear programming Reduce number of heat exchangers breaking heat loops stream splitting

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Selection of minimum-approach temperature is key design variable T1 T2 Q T0 ΔT min T ( 29 0 0 0 1 2 1 2 1 1 T T T LW Q Q Q T T T T T = × - + - × - = × × ÷ ÷ ×
Example Ts(oF) Tt(oF) mCp (BTU/hr/°F) C1 120 20,000 235 C2 180 40,000 240 H1 260 30,000 160 H2 250 15,000 130

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Stream T s (°F) T t (°F) mC P BTU/(hr ⋅° F) Q BTU/hr C1 120 235 20,000 2,300,000 C2 180 240 40,000 2,400,000 4,700,000 H1 260 160 30,000 3,000,000 H2 250 130 15,000 1,800,000 4,800,000 Minimizing Utilities in Heat Integration Designers choose ΔTmin then stream-matching procedure places heat exchangers.
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