An upgraded superstructure-based model for simultaneous synthesis of direct work and heat exchanger networks

Abstract

The optimal work and heat integration for pressure and temperature manipulation has been brought into sharp focus due to its paramount significance in reaching considerable energy and expenditure savings. This article proposes an upgraded stage-wise superstructure that simultaneously performs heat integration among unclassified hot/cold streams and direct work integration between pre-classified high/low-pressure streams. An efficiently innovative optimization model for the cost-effective synthesis of direct work and heat exchanger networks (WHENs) is established. A key strategy is to implement the identification of stream types (hot/cold). To this end, an improved superstructure-based model is presented for heat exchanger networks synthesis, combined with an optimized selection of multiple pressure-manipulation units in each stage of the WHEN superstructure. Besides, the proposed method can surpass certain limitations in previous studies that the coupling of direct work integration and heat integration is not considered. Our approach can effectively design preferable WHEN configurations and offer an alternative for enhancing thermal and mechanical energy recovery at the lowest total annual cost. Two case studies are conducted to assess the effectiveness of our proposed methodology, in which the better configurations can be obtained with considerable cost savings of 39.2% and 6.8% when compared to the corresponding literature solutions, respectively.