Title: The Use of Computational Fluid Dynamics (CFD) in Achieving Energy Reductions in New Zealand
1The Use of Computational Fluid Dynamics (CFD) in
Achieving Energy Reductions in New Zealands
Industrial Energy Consumption
Martin Atkins
- Energy Research Group
- Department of Engineering
- University of Waikato
2 Presentation Overview
- Industrial Energy Usage in NZ
- What is CFD?
- How can CFD Save Energy?
- Industrial Air Heater Example
- Pulp Screening Example
- Obstacles to Uptake
3NZ Energy Usage by Sector
PJ
Total NZ Energy Use 490 PJ
Energy Overview, Ministry of Economic
Development, 2002.
4NZ Industrial Energy Use
Energy Overview, Ministry of Economic
Development, 2002.
5 What is CFD?
- Computational Fluid Dynamics involves
- Numerical simulation of complex
- Fluid flow
- Heat transfer
- Mass transfer
- Chemical reactions/processes
6 The Basic CFD Process
Define Simplify Problem
Experimental Plant Data
Create Geometry Mesh
Define Boundary Conditions Model Parameters
Solving
Verification Validation
Post Processing
7How can CFD help reduce energy use?
- Increase Process Insight Understanding
- Fundamental understanding is vital for
optimisation - Move away from a black box approach
- Optimise Process Settings
- Can see effects of changes without altering the
process - Evaluate Possible Alterations
- Extend Experimental Work
- Can gain data that is difficult to measure
experimentally
8 Example 1 Industrial Spray Dryer
9 Industrial Air Heater
10Industrial Air Heater
- Diffuser
- Used to slow spread high velocity air from the
fan
- Centrifugal Supply Fan
- Sizing 5kW to 300kW
Flow Contraction
Hot air leaves to drier
- Air Inlet
- May have pre-filter
- Air flow rates between 5 T/hr and 350 T/hr
depending on unit size
- Heat Exchanger
- Typically between 300 kW and 25MW in rating,
thermal energy is transferred through three main
mediums - Condensing steam
- Heated oil
- Flue gas heating - Direct Gas Fired
11 2D Diffuser Flow Regimes
12 Flow Distribution Problems
- Flow distribution problems
- High fan power required
- Low heat exchanger efficiency
- Potential increase in maintenance costs
13 Improved Flow Distribution
- Potential savings
- Fan power
- Increased thermal efficiency of the heat
exchanger - Tube maintenance
14 Benefits Specific Energy Reduction
- Reduction in condensate temperature
- Increased efficiency of the steam use
- Increased production 3 4
- Reduced specific energy
- Reduced possible tube failure
15Example 2 Pulp Pressure Screen
- Used to screen pulp
- Complex flow fields due to screen rotor
16Rotor Pressure Pulse
- Pressure pulse
- Forward reverse flow occurs through the screen
during each pressure pulse
17Capacity Pulse Magnitude
Data from Luukonen et al, 2007
18Optimise Rotor Element
19Low Energy Rotor
20Capacity Power Consumption
Data from Luukonen et al, 2007
- Increasing tip speed
- Increases pressure pulse magnitude
- Increases capacity
- Increases power
21Rotor Power Rotor Speed
Data from Luukonen et al, 2007
22Canfor-Northwood SW Kraft Trial
52 Energy Savings
Data from Luukonen et al, 2007
23Obstacles to Uptake in NZ
- Cost
- Single Commercial license US20K per year
- Computational Costs
- Relatively low RD spend
- Lack of expertise
- Lack of understanding of potential benefits
- Turn around time
- Unsure of CFD capabilities applications
24Important Considerations
- What are you trying to achieve?
- Model Verification Validation
- Verification - Is the model correctly
implemented? Independent? - Validation - Is it realistic? Real world?
25 Conclusions
- CFD can be a powerful engineering tool for use in
energy reduction - Can increase understanding of the process and
important variables - Validation Verification is important for good
results
26 Acknowledgements
- Waikato Energy Research Group
- Prof. Peter Kamp
- Dr Michael Walmsley
- Jonas Hoffmann - Vocke
- University of Waikato
27