Cost Effective Heat Exchanger Network Design with Mixed Materials of Construction

Document Type: Research Article

Authors

1 Department of Chemical Engineering, Tarbiat Modarres University, Tehran, I.R. IRAN

2 Department of Chemical Engineering, Tehran University, Tehran, I.R. IRAN

Abstract

This paper presents a simple methodology for cost estimation of a near optimal heat exchanger network, which comprises mixed materials of construction. Intraditional pinch technology and mathematical programming it is usually assumed that all heat exchangers in a network obey a single cost model. This implies that all heat exchangers  in a network are of the same type and use the same materials of construction (an assumption that is unwarranted). The method introduced in this article enables the designer to decomposes the total cost of a heat exchanger into two elements, namely cost of the tubes and cost of the shell, thereby predict a more reliable cost for the network. By subsequent use of the binary variables and evaluation of the physical conditions of the streams, one can assign the streams to pass either through shell or tubes. Whereby, shell and tubes can be of different materials and therefore different cost models can be applied. Another advantage of the approach is that the pressure drop in each side of the exchanger (shell or tubes) can be assessed leading to more accurate evaluation of corresponding heat transfer coefficient for each individual stream. Finally an objective function (total cost) can be defined based on mixed materials of construction and different values of heat transfer coefficients.The proposed model has been utilized in three different case studies and the results are compared with those of a commercially available software (SUPERTARGET). The comparison shows reductions of more than 17% and 14% in total annual costs in the two cases, and 2.5% reduction in third, confirming the fact that more accurate evaluation of heat transfer coefficient for each individual stream can lead to better network design.

Keywords


[1] Gundersen T. and Naess, The Synthesis of Cost Optimal Heat Exchanger Network Synthesis- A Industrial Rreview of the State of the Art., Computers chem. Engng, 12, 503 (1988).

[2] Gundersen T., Sagli, B. and Kiste, K., Problems in Sequential and Simultaneous Stategies for Heat Exchanger Networks Synthesis. Computer-oriented Process Engineering, Elsevier Science, Amsterdam (1991).

[3] Linnhoff, B., Pinch Analysis- A State of the Rrt Review, Trans. Inst. Chem. Engrs, 71, part A (1993).

[4] Jezowski J., Heat Exchanger Network Grassroot and Retrofit Design, The Review of the State of the Art: Part II, Heat Exchanger Network Synthesis by Mathematical Methods and Approaches for Retrofit Design, Hungarian Journal of  Industrial  Chemistry Veszprem, 22, p. 295 (1994).

[5] Kravanja, a. and Grossmann, I. E., New Developments and capabilities in Prosyn – an Automated Topology and Parameter Process Synthesizer, Computers Chem. Engng., 18, 1097 (1994).

[6] Hall S. G., Ahmad S. and Smith, R., Capital Cost Targets for Heat Exchanger Networks Comprising Mixed Materials of Construction, Pressure Ratings and Exchanger Types, Computers Chem. Engng., 14, 319 (1990).

[7] Colberg, R.D., Morari, M., Area and Capital Cost Targets for Heat Exchanger Network Synthesis with Constrained Matches and Unequal Heat Transfer Coefficients, Comp. & Chem. Eng., 14 (1), p. 1 (1990).

[8] Jegede,F.O., Polley, G.T., “Capital Cost Targets for Networks with Non-Uniform Heat Exchanger Specifications”, Comp. & Chem. Eng., 16 (5), 477 (1992).

[9] Yee, T. F. and Grossmann, I. E., Simultaneous Optimization Models for Heat Integration-II. Heat Exchanger Network Synthesis, Computers Chem. Engng., 14, 1165 (1990).

[10] Shenoy,U.V., Heat Exchanger Network Synthesis, Gulf Publishing Co., Houston,Texas, (1995).

[11] Gundersen,  T.,  Grossmann,  I. E.,  Improved Optimization Strategies for Automated Heat Exchanger Network Synthesis Through Physical Insights, Comp. & Chem. Eng., 14 (9) 925 (1990).