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Abstract: In this paper, the new approach of constructal theory has been employed to design shell and tube heat exchangers. Constructal theory is a new method for optimal design in engineering applications. The purpose of this paper is optimization of shell and tube heat exchangers by reduction of total cost of the exchanger using the constructal theory. The total cost of the heat exchanger is the sum of operational costs and capital costs. The overall heat transfer coefficient of the shell and tube heat exchanger is increased by the use of constructal theory. Therefore, the capital cost required for making the heat transfer surface is reduced. Moreover, the operational energy costs involving pumping in order to overcome frictional pressure loss are minimized in this method. Genetic algorithm is used to optimize the objective function which is a mathematical model for the cost of the shell and tube heat exchanger and is based on constructal theory. The results of this research represent more than 50% reduction in costs of the heat exchanger. [Copyright &y& Elsevier]

This paper addresses the optimal arrangement and design of a dual pressure heat recovery steam generator coupled to two steam turbines. A superstructure that embeds various alternative configurations is optimized considering the following two single objective functions: (a) the maximization of the total net power generation for a given total heat transfer area and (b) the minimization of the total heat transfer area for a given total net power. The optimal number of heat exchangers and pumps and how they should be connected are the discrete decisions. The dimensions and operating conditions are the continuous decisions. A discrete and continuous mathematical model is developed and logical propositions are used for discrete decisions. The results are compared with a reference case reported by other authors. The results indicated that the optimization of the proposed superstructure allowed to find a more efficient HRSG configuration. The obtained configurations differ from the configuration of the reference case in how the heat exchangers and pumps are connected. A considerable increase in about 8% of the total net power generation in (a) and a significant reduction in about 24% of the total heat transfer area in (b) are achieved when compared to the reference case. [ABSTRACT FROM AUTHOR]