Abstract
A method for finding the best (optimal) operating layout of heat exchangers in complicated thermal networks is developed in this paper. Computer algorithms are developed that take advantage of pinch technology and economic considerations, and exergetic constraints as well as conventional heat and mass balances. Our goals were to achieve minimum loss of exergy between hot and cold streams subject to practical system constraints. Furthermore, resulting networks should be limited to no more units than the theoretical minimum. The ultimate goal was to minimize investment and operating costs for a set of fixed overall system constaints.
These goals were realized by developing a computer-based nonlinear multiple objective optimization algorithm that included the elements discussed above. The final solution is a synthesis of the best system using the above-described mathematical formulation. Results for a 4-stream heat exchanger network are presented in terms of the minimum temperature difference at the pinch point. The influence of the minimum temperature difference on capital cost, heat transfer area, exergetic losses and second law efficiency of various heat exchangers in the network is presented.
