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Numerical investigations on a Trilateral Flash Cycle under system - - PowerPoint PPT Presentation

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2 nd International Conference on Sustainable Energy and Resource Use in Food Chains Numerical investigations on a Trilateral Flash Cycle under system off-design operating conditions Matteo Marchionni a , Giuseppe Bianchi a , Savvas A.Tassou a ,

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

RCUK Centre for Sustainable Energy Use in Food Chains

Numerical investigations on a Trilateral Flash Cycle under system off-design operating conditions

Matteo Marchionnia, Giuseppe Bianchia, Savvas A.Tassoua, Obadah Zaherb, Jeremy Millerb

aBrunel University London, Uxbridge UB8 3PH, United Kingdom bSpirax Sarco Engineering PLC, GL53 8ER Cheltenham, United Kingdom

Paphos, Cyprus 17-19 October 2018

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RCUK Centre for Sustainable Energy Use in Food Chains

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

  • M. Marchionni

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Outline

  • Overview on low grade waste heat potential
  • Modelling activities on Trilateral Flash Cycle (TFC) system
  • Off-design simulations
  • Sensitivity analysis
  • Conclusions and future work
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RCUK Centre for Sustainable Energy Use in Food Chains

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

  • M. Marchionni

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Waste Heat Potential (WHP)

  • Low thermal grade WHP in industry represents the 4% of the

world final energy consumption

  • Highest amount of heat rejected into the environment from the

energy intensive industrial sectors

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RCUK Centre for Sustainable Energy Use in Food Chains

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

  • M. Marchionni

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Waste Heat Potential

UK low thermal grade WHP accounts for almost 50 TWh (5.4% of the EU-28 WHP)

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RCUK Centre for Sustainable Energy Use in Food Chains

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

  • M. Marchionni

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TFC vs ORC

Heat recovery Energy conversion TFC Single phase, high 2nd law efficiency Larger density change, higher efficiency ORC Two-phase, compact heat exchangers Realistic expansion ratio, safer blade environment

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RCUK Centre for Sustainable Energy Use in Food Chains

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

  • M. Marchionni

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1D modelling approach

  • Heat recovery loop neglected
  • Hot/cold water as

heating/cooling source

  • Map based components
  • Power quantities purely

mechanical

  • REFPROP for fluid thermo-

physical properties

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RCUK Centre for Sustainable Energy Use in Food Chains

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

  • M. Marchionni

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Heater and condenser

Plate Heat exchanger model Refrigerant inlet temperatures Refrigerant mass flow rate Temperatures

  • f the hot/cold

source

OUTPUTS

  • Refrigerant Quality
  • Heat exchangers pressure drops
  • Working fluid outlet temperatures

SWEP model

  • Several working points
  • Off-design outputs

GT-SUITE

model

  • Geometrical data
  • Heat exchanger material
  • Off-design points

Map

  • Best fitting coefficient of Nusselt-

Reynolds based correlations

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RCUK Centre for Sustainable Energy Use in Food Chains

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

  • M. Marchionni

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Heat transfer correlations

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  • 1-D discretization
  • Heat transfer correlations depending
  • n heat exchanger and fluid phase
  • Rayleigh-Plesset equation to predict

vapor formation and two-phase region extension

  • Heat exchanger inertia depending on

material and geometrical features

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RCUK Centre for Sustainable Energy Use in Food Chains

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

  • M. Marchionni

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Pump and expander

Input data

  • Revolution speed
  • Pressure rise
  • Power consumption

Process data

  • Interpolation between 2000 and

3500 RPM

  • Isentropic efficiency from power

consumption

Performance maps

PUMP EXPANDER

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RCUK Centre for Sustainable Energy Use in Food Chains

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

  • M. Marchionni

Reference conditions

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System performance

Heat load [kW] 2001 Heat rejected [kW] 1917 Pump power consumption [kW] 23 Expanders power [kW] 110 Net power output [kW] 86 Expander efficiency [%] 74.0 Thermal efficiency [%] 4.3

7.84 kg/s 130.30 kg/s 12°C 17°C 85°C 25°C P3=6.4 bar T3=63°C x3=0.11 P4=1.2 bar T4=20°C x4=0.4 24.65 kg/s

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RCUK Centre for Sustainable Energy Use in Food Chains

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

  • M. Marchionni

Off-design simulation matrix

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Min Reference Max

Temperature heat source [°C] 75 85 95 mass flow rate hot source [kg/s] 5.84 7.84 10.19 Expanders speed [RPM] 3000 4500 6000 Pump speed [RPM] 2500 3000 3500 Control valve opening 9% 100% 100%

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RCUK Centre for Sustainable Energy Use in Food Chains

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

  • M. Marchionni

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Expander revolution speed

  • Expander efficiency considerably affected by its revolution speed
  • Maximum power occurs at the optimal expander operating point (pump power fixed by the speed)
  • The highest quality of the refrigerant occurs close to the optimal operating point of the expander
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RCUK Centre for Sustainable Energy Use in Food Chains

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

  • M. Marchionni

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Pump revolution speed

  • Expander performance barely affected by a change in the pump revolution speed (drop of the volumetric

efficiency caused by a lower refrigerant quality is balanced by the increased mass flow rate of the working fluid due to the rise of the pump speed)

  • Net power output decreases due to increased pump power consumption
  • Cycle efficiency drops due to net power output decrease and heat recovery increase
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RCUK Centre for Sustainable Energy Use in Food Chains

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

  • M. Marchionni

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Hot source inlet temperature

  • No influence on the expander efficiency
  • Greater impact on outlet quality at the heater than on the cycle pressure ratio
  • Higher power output is due to a greater volume flow rate at the expander inlet
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RCUK Centre for Sustainable Energy Use in Food Chains

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

  • M. Marchionni

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Hot source mass flow rate

Same effects than previous case but with smoother trends

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RCUK Centre for Sustainable Energy Use in Food Chains

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

  • M. Marchionni

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Control valve opening area

  • Refrigerant quality at the expander inlet, and so the power output, increase

when the control valve is operated

  • No effect is shown on the expander efficiency
  • Thermal efficiency resembles the net power output trend (thermal load fixed)

https://doi.org/10.1016/j.ijrefrig.2018.02.001

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RCUK Centre for Sustainable Energy Use in Food Chains

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

  • M. Marchionni

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Sensitivity analysis

  • The expander revolution speed and the hot source inlet temperature present a more pronounced

effect on the system power output

  • Pump revolution speed and control valve opening affect deeply the refrigerant quality at the expander

inlet.

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RCUK Centre for Sustainable Energy Use in Food Chains

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

  • M. Marchionni

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Conclusions

  • The closing of the control valve increases the refrigerant quality at the expander

inlet and consequently the power output of the machine

  • The expander revolution speed should be varied in a narrow range close to its
  • ptimal operating condition
  • The hot source inlet conditions affect deeply the net power output of the system

due to a higher refrigerant quality at the expander inlet rather than an increased expansion ratio across the machine

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RCUK Centre for Sustainable Energy Use in Food Chains

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

  • M. Marchionni

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Future work

  • Experimental validation of the model implemented through an industrial

scale prototype unit

  • Development of a control system to regulate and optimize the refrigerant

quality at the expander inlet

  • Coupling of the pump and expander with electric machine
  • Friction modelling in the twin screw expander
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RCUK Centre for Sustainable Energy Use in Food Chains

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

  • M. Marchionni

Acknowledgements

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Research presented in this paper has received funding from: (i) Innovate UK (project no. 61995-431253), (ii) Engineering and Physical Sciences Research Council UK (EPSRC), grant no. EP/P510294/1 and (iii) Research Councils UK (RCUK), grant no. EP/K011820/1.