Effect of cross-section geometry on the thermohydraulic - - PowerPoint PPT Presentation

2nd International Conference on Sustainable Energy and Resource Use in Food Chains

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Effect of cross-section geometry on the thermohydraulic characteristics of supercritical CO2 in minichannels

Lei Chai*, Savvas A Tassou

Institute of Energy Futures, Brunel University London

Paphos, Cyprus 17-19 October 2018

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Outline

• Introduction

– Why sCO2? Why minichannels?

• Computational method

– Element, model, boundary condition.

• Data acquisition

– Local and average parameters.

• Results and discussion

– Thermohydraulic performance, comparison with correlations.

• Future work

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Why sCO2?

• Environment-friendly, nontoxic, non-

flammable

• a zero net impact on climate change
• reduced emission of greenhouse gas
• high power density for power

generation

• transcritical refrigeration cycle
• supercritical Brayton cycle
• natural circulation loops

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Why minichannels?

• highly compact construction
• high heat transfer coefficient
• high pressure capability
• lower fluid inventory

Cross-section geometry exerts an influence on fluid flow and heat transfer

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Computational element and model

• standard k-ε model
• NIST real gas

thermophysical properties

• buoyant effect

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Lei Chai Why NIST real gas model?

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Boundary and operating conditions

• Constant heat flux for channel wall, velocity-inlet for channel

inlet, pressure-outlet for channel outlet

• Corresponding mass flux for the four cases are 545.6, 1629.5, 473.9 and 561.3 kg/(m2·s)

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Data acquisition

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Local fluid temperature

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Local heat transfer coefficient

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Local Nusselt number

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Local pressure drop

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Local friction factor

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Average thermohydraulic performance

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Comparison with heat transfer correlations

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Comparison with fluid friction correlations

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Lei Chai Future work – modeling for heater, recuperator, cooler

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Lei Chai Future work - numerical study for different flow passages

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Lei Chai Future work – sCO2 heat exchanger test facility

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Acknowledgements

• Engineering and Physical Sciences Research Council (EPSRC) of the UK

under research grants EP/P004636/1 and EP/K011820/1

• European Union’s Horizon 2020 research and innovation programme

under grant agreement No. 680599.

• The authors would like to acknowledge the financial support received by

the project funders and the industry partners.

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Thank you !

Lei Chai Savvas A Tassou lei.chai@brunel.ac.uk savvas.tassou@brunel.ac.uk