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Abstract: Coupling exothermic with endothermic reactions is proposed as a significant improvement in reactor performance and energy integration. Furthermore, it forms an initial step for process optimization using pinch method. Through coupling of the exothermic reaction with endothermic one, oxidation with reduction, dehydrogenation with hydrogenation, hydration with dehydration, and even a series of tandem reactions, the utilization of energy and materials can be optimized. The underlying goal of this paper is to provide an extensive review through the years 1994–2011 of coupling exothermic and endothermic reactions as an important measure in process integration and intensifying. Developments in coupled reactions, classifying suitable reactors for couplings and categorizing several types of coupling exothermic and endothermic reactions are investigated in this study. Finally, various information concerning coupled reactions are presented in tables. Superiorities of novel models (coupled configurations) to the conventional configurations are clarified. Ultimately, various suggestions are proposed for further work. Results show that the short distance between heat sink and heat source can increase the efficiency of the heat transfer meanwhile incorporating two separated processes with coupled reactors can reduce the size of equipment. [Copyright &y& Elsevier]

Abstract: Improving the heating performance of district heating networks (DHNs), one of the most important components in district heating systems, has significant influence on the promotion of energy efficiency. Based on the entransy theory, this paper develops an entransy dissipation-based method for global optimization of DHNs. We analyze the irreversibility of three types of heat transfer processes in DHNs: (1) the heat transfer process between the waters in primary heating networks and DHNs in substation heat exchangers; (2) the heat transfer process between supply water and indoor airs in radiators; and (3) the return water mixing process, then derive the expressions of entransy dissipation for each process, and finally deduce two different formulas of the total entransy dissipation in DHNs by the users’ demands and the structural and operating parameters of DHNs, respectively, from which we establish the mathematical relation between the users’ demands and the structural and operating parameters of DHNs. Based on this relation, two typical optimization problems of DHNs are converted into conditional extremum problems to deduce two optimization equation groups. Solving the equation groups gives the optimal structural and operating parameters for DHNs with highest energy efficiency. Finally, the method is proved valid and advantageous through the optimization for both 1-column-2-user and 2-column-4-user DHNs. [Copyright &y& Elsevier]