2nd International Conference on Sustainable Energy

and Resource Use in Food Chains

RCUK Centre for Sustainable Energy Use in Food Chains

Numerical study of the thermohydraulic

performance of printed circuit heat

exchangers for supercritical CO2 Brayton

cycle applications

Lei Chai*, Savvas A Tassou

Institute of Energy Futures, Brunel University London

Paphos, Cyprus 17-19 October 2018

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2nd International Conference on Sustainable Energy

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Outline• Introduction

– Why sCO2? Why printed circuit heat exchanger?

• Computational method

– Element, model, boundary condition.

• Data acquisition

– Local, average and overall parameters.

• Results and discussion

– Thermohydraulic performance, comparison with correlations.

• Future work

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2nd International Conference on Sustainable Energy

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Why sCO2?

• working fluid with a

high power density

• smaller equipment sizes

• smaller plant footprint

• lower capital cost

• use of standard materials

• improved electrical-power-

conversion efficiency

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2nd International Conference on Sustainable Energy

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Why printed circuit heat exchanger?

Recuperator

• increase the average

temperature of the heat source

• results in higher efficiencies

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2nd International Conference on Sustainable Energy

and Resource Use in Food Chains

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Why printed circuit heat exchanger?

• highly compact construction

• high heat transfer coefficient

• high pressure capability

• wide range of operating

temperatures

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2nd International Conference on Sustainable Energy

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Computational element and model

• standard k-ε model

• NIST real gas

thermophysical

properties

• buoyant effect

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Boundary and operating conditions

• Periodic for upper and lower surfaces

• Symmetry for left and right surfaces

• Mass-flow-rate for two inlet

• Pressure-outlet for two outlet

• Mass flux balances: 254.6 to 1273.2 kg/(m2·s)

• Cold side :100 °C of inlet temperature and 150 bar of outlet pressure

• Hot side: 400 °C of inlet temperature and 75 bar of outlet pressure

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2nd International Conference on Sustainable Energy

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Data acquisition

Local thermohydraulic parameters

Average thermohydraulic parameters

Overall thermohydraulic parameters

z

z

GDRe

z

z

w,z f,z

qh

T T

z

z

f,z

h DNu

2z

z f2 D dp

Gf

dz

z0

L

Re dzRe

L z0

L

h dzh

L z0

L

Nu dzNu

L z0

L

f dzf

L

m

UQ

A T

hi co ho ci

m

hi co

ho ci

( ) ( )

ln( )

T T T TT

T T

T T

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2nd International Conference on Sustainable Energy

and Resource Use in Food Chains

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Validation of CFD model

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2nd International Conference on Sustainable Energy

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Local heat transfer coefficient

G = 763.9 kg/(m2·s)

z = 136 mm

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2nd International Conference on Sustainable Energy

and Resource Use in Food Chains

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Local pressure drop

G = 763.9 kg/(m2·s)

z = 136 mm

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2nd International Conference on Sustainable Energy

and Resource Use in Food Chains

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Average thermohydraulic performance

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2nd International Conference on Sustainable Energy

and Resource Use in Food Chains

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Overall thermohydraulic performance

RCUK Centre for Sustainable Energy Use in Food Chains

2nd International Conference on Sustainable Energy

and Resource Use in Food Chains

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Comparison with prediction from empirical correlation

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2nd International Conference on Sustainable Energy

and Resource Use in Food Chains

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Comparison with prediction from empirical correlation

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2nd International Conference on Sustainable Energy

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Future work – modeling for heater, recuperator, cooler

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Future work - numerical study for different flow passages

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2nd International Conference on Sustainable Energy

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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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2nd International Conference on Sustainable Energy

and Resource Use in Food Chains

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Thank you !

Lei Chai Savvas A Tassou

lei.chai@brunel.ac.uk savvas.tassou@brunel.ac.uk