Optimization model for re-circulating cooling water systems

This paper presents an optimization model for the simultaneous synthesis and detailed design of re-circulating cooling water systems. A cooler network superstructure that embeds all network configurations of practical interest is used as part of the integrated model. Pressure drops in each cooler are treated as optimization variables, and design guidelines and constraints are included in order to provide practical and feasible units. The model is based on a generalized disjunctive programming formulation, which gives rise to a mixed-integer nonlinear programming problem. The objective is to find cooling water systems that minimize the total annual cost. Solution of this mathematical formulation provides the optimal system configuration as well as the optimal operating conditions and design parameters required for each cooler unit in the network and in the cooling tower. Three example problems are presented to show the application of the proposed approach.