Equilibrio Multifásico Vll

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Applied Thermal Engineering 31 (2011) 3615e3628Contents lists available at ScienceDirect

Applied Thermal Engineering
journal homepage: www.elsevier.com/locate/apthermeng

Optimization of mechanical draft counter flow wet-cooling towers using a rigorous model
Eusiel Rubio-Castro a, Medardo Serna-González a, *, José María Ponce-Ortega a, Miguel Angel Morales-Cabrera b
a b

Chemical Engineering Department, Universidad Michoacana de San Nicolásde Hidalgo, Ciudad Universitaria, Edificio V1, Morelia, Michoacán 58060, Mexico Chemical Engineering Department, Universidad Veracruzana, Poza Rica, Veracruz, Mexico

a r t i c l e i n f o
Article history: Received 26 April 2011 Accepted 17 July 2011 Available online 22 July 2011 Keywords: Counter flow cooling towers Poppe method Merkel method Rigorous optimization

a b s t r a c t
In thispaper, an optimal design algorithm for mechanical draft counter flow wet-cooling towers based on the rigorous Poppe model and mixed-integer nonlinear programming (MINLP) is presented. Unlike the widely used Merkel method, the Poppe model takes into consideration the effects of the water loss by evaporation and the nonunity of the Lewis factor. As a result, the Poppe model is able to predict theperformance of wet-cooling towers very accurately compared to the Merkel method. The optimization problem is formulated as an MINLP model by considering all the mass and energy balances, equations for physical properties, and empirical correlations for the loss and overall mass transfer coefficients in the packing region of the tower, in addition to feasibility constraints. The objective function to beminimized is the total annual cost, which includes capital and operating costs. The mathematical programming problem is solved with the GAMS software. Six case studies are used to show the application of the proposed algorithm. The case studies demonstrate that there can be large differences between the optimal designs based on the Poppe method and the Merkel method. Ó 2011 Elsevier Ltd. All rightsreserved.

1. Introduction Along to the industrial history, the process engineers have looked for strategies and methodologies to minimize the process costs and to increase the profits. In this area, the mass [1] and thermal water integration [2,3] have represented an important role. Regarding to the thermal water integration, several strategies have been reported around the open re-circulatingcooling water systems, because they are widely used to dissipate the low-grade heat of chemical and petrochemical process industries, electricpower generating stations, refrigeration and air conditioning plants. In all these systems, water is used to cool down the hot process streams, and then this water is cooled by evaporation and direct contact with air in a wet-cooling tower and recycled tothe cooling network. Therefore, the cooling towers are very important industrial components and there are many references that present the fundamentals to understand these units [4e6]. The first practical theory of counter flow cooling towers was developed by Merkel [7]. In this theory, the water loss due to

* Corresponding author. Tel.: þ52 443 3273584. E-mail address: mserna@umich.mx (M....