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Open AccessArticle

On the Conceptual Design of Novel Supercritical CO2 Power Cycles for Waste Heat Recovery

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Department of Industrial Engineering, University of Padova, via Venezia 1, 35131 Padova, Italy
2
IDMEC, Mechanical Engineering Department, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal
*
Author to whom correspondence should be addressed.
Energies 2020, 13(2), 370; https://doi.org/10.3390/en13020370
Received: 24 November 2019 / Revised: 31 December 2019 / Accepted: 9 January 2020 / Published: 12 January 2020
The supercritical CO2 power cycle (s-CO2) is receiving much interest in the utilization of waste heat sources in the medium-to-high temperature range. The low compression work and highly regenerative layout result in high thermal efficiencies, even at moderate turbine inlet temperatures. The capability of heat extraction from the waste heat source is, however, limited because the heat input takes place over a limited temperature range close to the maximum cycle temperature. Accordingly, novel s-CO2 layouts have been recently proposed, aimed at increasing the heat extraction from the heat source while preserving as much as possible the inherently high thermal efficiency. Among these, the most promising ones feature dual expansion, dual recuperation, and partial heating. This work concentrates on the conceptual design of these novel s-CO2 layouts using a systematic approach based on the superimposition of elementary thermodynamic cycles. The overall structure of the single flow split with dual expansion (also called cascade), partial heating, and dual recuperated cycles is decomposed into elementary Brayton cycles to identify the building blocks for the achievement of a high performance in the utilization of waste heat sources. A thermodynamic optimization is set up to compare the performance of the three novel layouts for utilization of high temperature waste heat at 600 °C. The results show that the single flow split with a dual expansion cycle provides 3% and 15% more power compared to the partial heating and dual recuperated cycles, respectively, and 40% more power compared to the traditional single recuperated cycle used as the baseline. The separate evaluation of thermal efficiency and heat recovery effectiveness shows the main reasons behind the achievement of the highest performance, which are peculiar to each novel layout. View Full-Text
Keywords: supercritical CO2 power cycles; waste heat recovery; partial heating; dual recuperated; dual expansion; cascade supercritical CO2 power cycles; waste heat recovery; partial heating; dual recuperated; dual expansion; cascade
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Manente, G.; Costa, M. On the Conceptual Design of Novel Supercritical CO2 Power Cycles for Waste Heat Recovery. Energies 2020, 13, 370.

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