Numerical modelling and performance maps of a printed circuit … Presentatio… · Printed Circuit Heat Exchanger (PCHE) RCUK Centre for Sustainable Energy Use in Food Chains 2nd

2nd International Conference on Sustainable Energy

and Resource Use in Food Chains

RCUK Centre for Sustainable Energy Use in Food Chains

Numerical modelling and performance maps of a

printed circuit heat exchanger for use as

recuperator in supercritical CO2 power cycles

Matteo Marchionni*, Lei Chai, Giuseppe Bianchi,

Savvas A.Tassou

Brunel University London, Uxbridge UB8 3PH, United Kingdom

Paphos, Cyprus 17-19 October 2018




M. Marchionni 2

Presentation outline

• Overview on sCO2 heat to power systems

• 3D CFD model

• 1D CFD approach

• 1D/3D results comparison

• 630 kW PCHE calibration

• PCHE performance maps

• Conclusions and future work




M. Marchionni 3

Why sCO2?

CompactnessLow

environmental impact

High efficiency




M. Marchionni 4

sCO2 power cycles

+7%

+7% efficiency if coupled with an

ORC or other cascade systems




M. Marchionni 5

sCO2 power cycles for WHR

High sCO2thermal stability

Reduced footprint and

costs

Reduced water

consumptions




M. Marchionni 6

Heat exchangers in sCO2 systems • Harsh operating conditions

• High temperature gradients

• Intense thermal duties

• Key components

Printed Circuit Heat Exchanger (PCHE)




M. Marchionni 7

3D CFD model

• 3D CFD model of a PCHE elementary heat

transfer unit developed in ANSYS FLUENT

• Periodic and symmetry boundary conditions

• standard k-ε turbulence model

• SIMPLEC algorithm to couple the pressure

and velocity field

• Buoyancy and entrance effect are

considered




M. Marchionni 8

1D modelling procedure

• The channel are discretized along

the flow direction

• Geometrical features of the

channel cross-section are set

• Dittus-Boelter heat transfer

correlation

• Colebrook equation




M. Marchionni 9

Simulation setup

9

• Geometrical features of the PCHE

elementary unit are defined

• Identical boundary conditions are set

• Channel surface roughness neglected

• Material thermophysical properties as

function of its temperature

• Reduced computational effort

• NIST Refprop dll for the calculation of

the CO2 thermophysical properties

Geometrical features and materials of the test case

Wetted parameter [mm] 5.14

Hydraulic diameter [mm] 1.22

Cross-sectional area [mm2] 1.57

Length [mm] 272.00

Plate thickness [mm] 1.63

Surface roughness Neglected

Material Stainless steel 316L

Simulation setups

Boundary conditions Cold side Hot side

Mass flux [kg/(sm2)] 509.3

Inlet temperature [°C] 100 400

Outlet pressure [bar] 150 75

1D 3D

Spatial discretization [mm] 6.8




M. Marchionni 10

1D/3D comparison

• Temperatures and pressures in several sections of the cold and hot channel match

• The heat transfer coefficient predictions of the two models present an offset, which is mainly due to the

different calculation procedures adopted

• The 1D modelling approach cannot predict the thermal entrance effect in the PCHE channels




M. Marchionni 11

1D model calibration of a 630 kW PCHE

630 kW PCHE characteristics

Channel geometry

Wetted parameter [mm] 5.14

Hydraulic diameter [mm] 1.22

Cross-sectional area [mm2] 1.57

Length [mm] 1012

Type Straight

PCHE properties

Material Stainless steel 316L

Channel surface roughness Neglected

Channel discretization length [mm] 25.3

Number of channels per row 54

Number of rows 42




M. Marchionni

Calibration results

12

Design (1) Off-design #1 (2) Off-design #2 (3) Off-design #3 (4) Off-design #4 (5)

mass flow rate [kg/s] 2.06 1.57 2.09 2.09 2.62

cs temp in [°C] 72.9 72.9 875 62.0 72.9

60

90

120

150

180

210

0 1 2 3 4 5

Pre

ssu

re d

rop

[kP

a]

Case

60

120

180

240

300

0 1 2 3 4 5

Te

mp

era

ture

[°C

]

Case

400

500

600

700

800

0 1 2 3 4 5

He

at lo

ad

[kW

]

Case

The highest error of 5.7% is shown for the pressure drop on the cold side in the 4th off-design case




M. Marchionni 13

Performance maps1.57 kg/s (75% of the design case) 2.06 kg/s (design point) 2.62 kg/s (125% of the design case)

• A reduction of the cold side inlet pressure increments the thermal power exchanged by the PCHE

• The thermal power exchanged rises accordingly to the hot side inlet temperature




M. Marchionni 14

Overall heat transfer coefficient1.57 kg/s (75% of the design case) 2.06 kg/s (design point) 2.62 kg/s (125% of the design case)

• The increase of the sCO2 mass flow rate, the hot side inlet temperature and the cold side inlet pressure

have a beneficial effect on the overall heat transfer coefficient




M. Marchionni 15

Effectiveness1.57 kg/s (75% of the design case) 2.06 kg/s (design point) 2.62 kg/s (125% of the design case)

• An increased mass flow rate and inlet pressure of the cold side negatively affect the effectiveness of the

PCHE

• A rise of the effectiveness can be observed when the inlet temperature of the hot side is incremented




M. Marchionni 16

Pressure drops1.57 kg/s (75% of the design case) 2.06 kg/s (design point) 2.62 kg/s (125% of the design case)

• An increment of the hot side inlet temperature and the working fluid mass flow rate cause higher pressure

losses across the heat exchanger

• On the contrary, an increase of the cold side inlet pressure is beneficial for the reduction of the PCHE

overall pressure drop




M. Marchionni 17

Conclusions

• A 1D modelling procedure has been herein presented, the approach validated by

means of a 3D CFD model of a PCHE heat transfer elementary unit

• A 630 kW PCHE, which will be used in the sCO2 test rig at BUL, has been modelled

• Performance maps of the heat exchanger have been reported as a function of the

working fluid mass flow rate, the hot side inlet temperature and the cold side inlet

pressure

• The results shown that several trade-off must be considered when selecting the

main cycle thermodynamic parameters




M. Marchionni 18

Future work

• Integration of the PCHE model developed in the

sCO2 power unit dynamic model

• Experimental validation of the modelling approach

through the test rig currently under construction at

Brunel University London

RECUPERATOR

waste heat recovery

station

compressor turbine

gas cooler

generator




M. Marchionni

Acknowledgements

19

This project has received funding from the European Union’s Horizon 2020 research and innovation

programme under grant agreement No. 680599

Documents

Numerical modelling and performance maps of a printed circuit … Presentatio… · Printed Circuit Heat Exchanger (PCHE) RCUK Centre for Sustainable Energy Use in Food Chains 2nd