An Exergy-based MILP algorithm for Heat Pumps Integration in industrial processes

F. Thibault, A. Zoughaib, S. Jumel
4.070 703

Abstract


Industrial heat pumps are efficient thermodynamic systems able to recover low grade heat and deliver it at higher temperatures (up to 120°C for the current available solutions). They are identified as a very efficient way to reduce primary energy consumption in processes, especially in food & drink or pulp & paper industries. Nevertheless, the optimal integration of multiple heat pumps in a large process with numerous heat fluxes is challenging. The present paper aims at describing an algorithm that was developed for this purpose, based on the GCC (Grand Composite Curve) of Pinch Analysis and on Exergy Theory. The temperature scale of the GCC is divided in areas defined by the Main Pinch Point and Potential local Pinch Points. Then, every potential heat pump is evaluated, absorbing heat in any area for delivering in an upper one. The corresponding heat load and COP are calculated. Exergy cost of remaining cold utilities is calculated with a Carnot based-efficiency, exergy cost of hot utilities according to their nature and temperature. The global exergy cost is used as criteria. Thanks to its formulation, the algorithm may suggest heat pumps solutions in non-obvious areas. The algorithm is tested on a literature case and shows equivalent or better exergy costs in a satisfying calculation time.

Keywords


Energy integration; exergy; heat pumps; MILP optimization

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DOI: http://dx.doi.org/10.5541/ijot.554

References


K.C. Furman, N.V. Sahinidis, Computational Complexity of heat exchanger network synthesis, Computers and Chemicals Engineering, Volume 25, February 2001, Pages 1371-1390

J. Schiffmann , D. Favrat , Design, experimental investigation and multi-objective optimization of a small-scale radial compressor for heat pump applications, Energy, Volume 35, Issue 1, January 2010, Pages 436-450.

H. Becker, Methodology and Thermo-Economic Optimization for Integration of Industrial Heat Pumps, PhD thesis, 2012, Lausanne, Switzerland : EPFL. R. Murr , H. Thieriot, A. Zoughaib, D. Clodic, Multiobjective optimization of a multi water-to-water heat pump system using evolutionary algorithm, Applied Energy, Volume 88, Issue 11, November 2011, Pages 3580-3591.

B. Linnhoff, Introduction to Pinch Technology; 1998, 26S. Papoulias, Grossmann I., A structural optimization approach in process synthesis—II , Computers & Chemical Engineering, Volume 7, Issue 6, 1983, Pages 707-721

X. Feng, X.X. Zhu, Combining pinch and exergy analysis for process modifications, Applied Thermal Engineering, Volume 17, Issue 3, March 1997, Pages 249