This paper presents a new approach for analyzing and/or synthesizing the heat regeneration system, which has many applications in various energy conversion plants (ECP) and between ones. The method is applied for optimizing heat exchanger networks (HENs) operating below ambient temperature conditions as an application for refrigeration machines. Exergy and exergoeconomic methods are adapted for the optimization of three-flow heat exchangers. Few cases are illustrated and discussed. Also, the heuristic rules and design criteria for pinch analysis for an optimized HEN are presented. (C) 2004 Elsevier Ltd. All rights reserved.