Design optimization and analysis of a multi-temperature partition and multi-configuration integrated organic Rankine cycle for low temperature heat recovery

Abstract

With the development of society and economy, more and more attention has been paid to energy saving where low temperature heat plays an important role. As an effective means to utilize low temperature heat, the organic Rankine cycle attracts great attention, where interval partition number, the optimization of interval temperature, system configuration optimization, working fluid selection and matching with heat source have significant influence on system performance. It is challenging to optimize organic Rankine cycle system considering these issues simultaneously. This study proposes a multi-temperature partition and multi-configuration integrated organic Rankine cycle system model to improve low temperature heat utilization and a comprehensive comparison with basic organic Rankine cycle, recuperative organic Rankine cycle and regenerative organic Rankine cycle is conducted to assess thermal and economic performance with ten working fluids. A numerical optimization analysis compared with other literature and the result of traversal, is performed to ensure the accuracy of mathematical models under the same settings. A series of thermal analysis for organic Rankine cycle systems with multiple system configurations, working fluids selection, condition of heat source and so on are implemented considering internal temperature optimization with evaporation temperature and regenerative ratio. A solution strategy framework is established for the proposed system models. In order to verify the practicability of the proposed model, a case study is built with refinery diesel as the heat source. The result shows that thermal efficiency of the proposed system model has an increase of 4.95–14.01 % compared with the basic organic Rankine cycle and the one with single interval temperature has better performance with 4.95 % higher thermal efficiency and 1.45 % higher total annual cost. Thus, the proposed system model and its corresponding solution strategy can be applied for low temperature heat recovery.