Methodology to develop off-design models of heat exchangers with non-ideal fluids
Article
Article Title | Methodology to develop off-design models of heat exchangers with non-ideal fluids |
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ERA Journal ID | 3658 |
Article Category | Article |
Authors | Bone, Viv, McNaughton, Rob, Kearney, Michael and Jahn, Ingo |
Journal Title | Applied Thermal Engineering |
Journal Citation | 145, pp. 716-734 |
Number of Pages | 19 |
Year | 2018 |
Publisher | Elsevier |
Place of Publication | United Kingdom |
ISSN | 1359-4311 |
1873-5606 | |
Digital Object Identifier (DOI) | https://doi.org/10.1016/j.applthermaleng.2018.09.082 |
Web Address (URL) | https://www.sciencedirect.com/science/article/pii/S1359431118326784 |
Abstract | Supercritical CO2 (sCO2) closed Brayton cycles are promising heat engines for next-generation thermal power plants since they are efficient, highly scalable, and compatible with a variety of heat sources. A potential application for these cycles is load-following concentrating solar power plants with thermal storage, which will frequently operate at off-design conditions. Accurate and computationally efficient models of the cycle’s heat exchangers and turbomachinery are required to assess and optimise its off-design performance. The printed circuit heat exchangers (PCHEs) used in the sCO2 closed Brayton cycle are challenging to model since they exhibit non-ideal-gas effects and typically use zigzag channels, for which flow patterns and heat transfer mechanisms are not completely understood. Moreover, heat transfer correlations that capture all effects relevant to a given geometry and flow conditions are often unavailable. We present a methodology to develop accurate and computationally efficient on- and off-design models of heat exchangers that exhibit complex nonlinear behaviours. This methodology involves fitting a 1D discretised heat exchanger model to experimental data using nonlinear least-squares optimisation. Unknown internal heat exchanger geometric parameters are used as fitting parameters. We demonstrate the proposed methodology by developing numerical models for two PCHEs: (1) an sCO2–sCO2 PCHE operating far from CO2’s critical point and (2) an oil–sCO2 PCHE operating close to CO2’s critical point, where non-ideal fluid property variations are significant. Test data spans heat loads from 6–48% and 15–39% of name-plate duty for heat exchangers (1) and (2) respectively. Across these operating ranges, the maximum and mean heat transfer prediction residuals are 0.91% and 0.36% for heat exchanger (1) and 3.04% and 1.24% for heat exchanger (2). Additionally, we show that good accuracy can be obtained when using only the channel hydraulic diameter as a fitting parameter. Due to their low computational cost and high accuracy, models developed using the proposed methodology are eminently suitable for off-design modelling and optimisation of the sCO2 closed Brayton cycle and other power cycles or industrial processes where heat exchangers exhibit complex nonlinear behaviour. |
Keywords | Heat exchanger; Printed circuit heat exchanger; Supercritical CO2 Brayton cycle; Off-design modelling; Optimisation; Model fitting |
Contains Sensitive Content | Does not contain sensitive content |
ANZSRC Field of Research 2020 | 4012. Fluid mechanics and thermal engineering |
Public Notes | Files associated with this item cannot be displayed due to copyright restrictions. |
Byline Affiliations | University of Queensland |
Commonwealth Scientific and Industrial Research Organisation (CSIRO), Australia |
https://research.usq.edu.au/item/z210z/methodology-to-develop-off-design-models-of-heat-exchangers-with-non-ideal-fluids
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