chemical engineering research and design 87 (2009) 200–209 Contents lists available at ScienceDirect Chemical Engineering Research and Design journal homepage: www.elsevier.com/locate/cherd Optimum design of cooling water systems for energy and water conservation M.H. Panjeshahi a,* , A. Ataei b , M. Gharaie c , R. Parand c a Department of Chemical Engineering, Tehran University, P.O. Box 11155-4563, Tehran, Iran b Department of Energy and Environment, Science and Research Campus, Azad University, P.O. Box 14515-775, Tehran, Iran c Department of Mechanical Engineering, K.N. Toosi University of Technology, P.O. Box 1999143344, Tehran, Iran abstract Re-circulating cooling water systems (RCWSs) are widely used to reject waste process heat to the environment, conserve fresh water and reduce thermal pollution relative to once-through systems. Research on RCWS has mostly focused on individual components, cooling tower and heat-exchanger network. Kim and Smith [Kim, J.K. and Smith, R., 2001, Cooling water system design, Chem Eng Sci, 56(12): 3641–3658] developed a grass-root design method of RCWS (KSD). In this paper, the KSD method is expanded and a comprehensive simulation model of RCWS is developed accounting for interaction between cooling tower and heat-exchanger network. Regarding this model, a modern grass-root design method of RCWS, we call it Advanced Pinch Design (APD), based on combined pinch technology and mathematical programming is developed for minimum cost achievement. Having considered cycle water quality through introducing ozone treatment technology, APD methodology is further improved. This technique that we call Enhanced Cooling Water System Design (ECWSD), as the APD supplementary methodology, is provided water and energy conservation, minimum cost and environmental impacts. Related coding in MATLAB version 7.1 is developed for the illustrative example to get optimal values in RCWS design method computations. Finally the results of the introduced grass-root design methodologies, APD and ECWSD, are compared with KSD. Crown Copyright © 2008 Published by Elsevier B.V. on behalf of The Institution of Chemical Engineers. All rights reserved. Keywords: Re-circulating cooling water system; Cooling tower; Pinch technology; Mathematical programming; Ozone treatment; Water-energy conservation 1. Introduction Re-circulating cooling water systems (RCWSs) are by far the most common industrial waste process heat rejection systems to the environment. RCWS provides conservational opportu- nity for water and energy and pollution reduction relative to once-through systems because of water re-use possibility. Previous related works, have been paid attention to issues of cooling water systems individually (Castro et al., 2000; Heikkila and Milosavljevic, 2001), water re-use and waste water minimization (Mann and Liu, 1999), numerical anal- ysis of heat and mass transfer inside a reversibly used water cooling tower (Deng and Tan, 2003) and other opera- tional aspects of cooling tower. Little consideration has been ∗ Corresponding author. Tel.: +98 21 88804272; fax: +98 21 88807687. E-mail addresses: mhpanj@ut.ac.ir (M.H. Panjeshahi), abtinataei@gmail.com (A. Ataei), mona.gharaie@gmail.com (M. Gharaie), rezaparand@gmail.com (R. Parand). Received 15 October 2007; Accepted 6 August 2008 placed to the interaction between cooling tower and heat- exchanger network. To RCWS design, the effect of any possible changes of the system components on the cooling perfor- mance should be predicted properly. Therefore, the directly interacted cycle components should be considered simulta- neously. Pinch technology as the most common design tools is helped. This technology is based on targeting before design and exploits conceptual understanding. Kim and Smith (2001) represented a grass-root design methodology of RCWS. Kim and Smith Design (KSD) method allowed the existing interactions within the cooling water sys- tem to be considered. In the KSD method, the maximum water re-use profile (minimum water flow rate) is participated in the design of the network configuration. Moreover, fix approach 0263-8762/$ – see front matter. Crown Copyright © 2008 Published by Elsevier B.V. on behalf of The Institution of Chemical Engineers. All rights reserved. doi:10.1016/j.cherd.2008.08.004