computational fluid dynamics approach, conservation equations and
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Computational fluid dynamics approach and its application in food processing
BYLavanya M NPh.D. (FPE)
• CFD is a simulation tool, which uses a power computer
and applied mathematics to model fluid flow situations.
• In 1928, the application of CFD started in fluid flow
• Daimler Chrysler was the first company to use CFD in
Automotive sector.
• Speedo was the first swimwear company to use CFD
• The adoption of CFD technology by food engineers
began in the 1990s.
Computational fluid dynamics approach
It provides qualitative and sometimes quantitative prediction
of fluid flow by
• Mathematical modelling (partial differential equations),
• Numerical methods (discretization and solution techniques),
• Software tools (solvers, pre- and post-processing utilities).
Computational fluid dynamics approach
FundamentalsThe fundamental basis of almost all CFD problems uses the set of
Navier–Stokes equations
• Governing the equation: conservation equations (Conservation of
mass, conservation of momentum and conservation of energy)
• Numerical analysis: The most important techniques are finite
difference, finite elements and finite volumes.
• Solving the flow problems
• Interpreting the solutions
Fundamentals of CFD
The analyst should have a knowledge to state
the problem and to use scientific knowledge to
express it mathematically
Stages in CFD
Pre-processing Processing Post-
processing
Problem thinking,
meshing and generation
of a computational
model.
Solving equations
Evaluation
The simulation and analysis within a CFD Stages
Pre-processing: meshing
Create shape of the problem domain
CAD/CAE integration
Engineering drawings
Coordinates include Cartesian
system (x,y,z), cylindrical system (r,
θ, z), and spherical system(r, θ, Φ)
Stages in CFD
Initial condition involves knowing the state of
pressure (p) and initial velocity (u) at all points
in the flow.
Boundary conditions such as walls, inlets and
outlets largely specify what the solution will be.
Geometry of problem is defined .
Volume occupied by fluid is divided into discrete
cells.
Stages in CFD
Pre-processing: Initial boundary conditions
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Problem domain: Example
• It involves computer to solve the
mathematical equations of fluid
flow
• Solves thousands of equations
• Equation discretization
Sample grid established by Gambit of FLUENT
Processing
• Calculation of derived variables
• Calculation of integral parameters: forces,
moments
• Visualization (usually with commercial
software)
• Simple X-Y plots
• Simple 2D contours
• 3D contour carpet plots
• Animations (dozens of sample pictures in
a series of time were shown
continuously)
Post-Processing: Evaluation of generated data
• Gives much better and deeper understanding of what is happening in a particular process or system.
• Less time and cost than would be involved in laboratory testing.
• It can answer many ‘what if’ questions in a short time.
• Reduce scale-up problems
• It is particularly useful in simulating conditions where it is not possible to take detailed measurements such as high temperature or dangerous environment in an oven.
• Since it is a pro-active analysis and design tool, it can highlight the root cause not just the effect when evaluating plant problems.
Advantages of CFD
Commercial codes for CFD
1. CFX
2. FLUENT
3. PHOENICS
4. STAR-CD
5. FLOW3D
6. CFD-ACE
7. ICM CFD
8. AMI-VSAERO
9. STORESIM/TETMESH
10. IGGTM
11. TECPLOT
12. PAM-FLOW
13. FLOVENT
14. AVS/EXPRESS
15. FLO++
16. CFD++
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Where is CFD used? (Aerospace)
• Where is CFD used?– Aerospace– Appliances– Automotive– Biomedical– Chemical Processing– HVAC&R– Hydraulics– Marine– Oil & Gas– Power Generation– Sports
F18 Store Separation
Wing-Body Interaction Hypersonic Launch Vehicle
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Where is CFD used? (Appliances)
• Where is CFD used?– Aerospace– Appliances– Automotive– Biomedical– Chemical Processing– HVAC&R– Hydraulics– Marine– Oil & Gas– Power Generation– Sports
Surface-heat-flux plots of the No-Frost refrigerator and freezer compartments helped BOSCH-SIEMENS engineers to optimize the location of air inlets.
16
Where is CFD used? (Automotive)
• Where is CFD used?– Aerospace– Appliances– Automotive– Biomedical– Chemical Processing– HVAC&R– Hydraulics– Marine– Oil & Gas– Power Generation– Sports
External Aerodynamics Undercarriage Aerodynamics
Interior Ventilation Engine Cooling
Where is CFD used? (Biomedical)
• Where is CFD used?– Aerospace– Appliances– Automotive– Biomedical– Chemical Processing– HVAC&R– Hydraulics– Marine– Oil & Gas– Power Generation– Sports
Temperature and natural convection currents in the eye following laser heating.
Spinal Catheter
Medtronic Blood Pump
18
Where is CFD used? (Chemical Processing)
• Where is CFD used?– Aerospace– Appliances– Automotive– Biomedical– Chemical Processing– HVAC&R– Hydraulics– Marine– Oil & Gas– Power Generation– Sports
Polymerization reactor vessel - prediction of flow separation and residence time effects.
Shear rate distribution in twin-screw extruder simulation
Twin-screw extruder modeling
19
Where is CFD used? (HVAC&R)
• Where is CFD used?– Aerospace– Appliances– Automotive– Biomedical– Chemical Processing– HVAC&R– Hydraulics– Marine– Oil & Gas– Power Generation– Sports
Particle traces of copier VOC emissions colored by concentration level fall behind the copier and then circulate through the room before exiting the exhaust.
Mean age of air contours indicate location of fresh supply air
Streamlines for workstation ventilation
Flow pathlines colored by pressure quantify head loss in ductwork
20
Where is CFD used? (Hydraulics)
• Where is CFD used?– Aerospace– Appliances– Automotive– Biomedical– Chemical Processing– HVAC&R– Hydraulics– Marine– Oil & Gas– Power Generation– Sports
21
Where is CFD used? (Marine)
• Where is CFD used?– Aerospace– Appliances– Automotive– Biomedical– Chemical Processing– HVAC&R– Hydraulics– Marine– Oil & Gas– Power Generation– Sports
22
Where is CFD used? (Oil & Gas)
• Where is CFD used?– Aerospace– Appliances– Automotive– Biomedical– Chemical Processing– HVAC&R– Hydraulics– Marine– Oil & Gas– Power Generation– Sports
Flow vectors and pressure distribution on an offshore oil rig
Flow of lubricating mud over drill bit
Volume fraction of water
Volume fraction of oil
Volume fraction of gas
Analysis of multiphase separator
23
Where is CFD used? (Power Generation)
• Where is CFD used?– Aerospace– Appliances– Automotive– Biomedical– Chemical Processing– HVAC&R– Hydraulics– Marine– Oil & Gas– Power Generation– Sports
Flow pattern through a water turbine.
Flow in a burner
Flow around cooling towers
Pathlines from the inlet colored by temperature during standard operating conditions
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Where is CFD used? (Sports)
• Where is CFD used?– Aerospace– Appliances– Automotive– Biomedical– Chemical Processing– HVAC&R– Hydraulics– Marine– Oil & Gas– Power Generation– Sports
Application of CFD in food industry: Drying
CFD to analyse the flow and performance of process equipment, such as• Baking ovens• Refrigerated display cabinets • Stirred tanks • spray dryers • Heat exchangers• some other equipment. In design and development,
CFD programs predict • Fluid flow behaviour, • Transfer of heat, mass (such as in perspiration or dissolution), • Phase change (such as in freezing, melting or boiling), • Chemical reaction (such as combustion or rusting), • Mechanical movement (such as an impeller turning, pistons, fans or
rudders)• Stress or deformation of related solid structures (such as a mast
bending in the wind).
Application of CFD in food industry
Application of CFD in food industry: DryingProblemDescriptions
Model geometry Software Findings Author
Evaluation of dropletdrying models ina spray dryer fittedwith rotary atomizerusing CFDsimulation
3D Fluent The concept ofparticle rigidityprediction in a CFDsimulation wasexplored and theeffect of initial feedmoisture content onthe drying modelswas also studied.
Woo et al. (2008a)
Simulation ofindustrial scale spraydryer attached witha Fluidized bed,using ReactionEngineeringApproach (REA).
2D Fluent Smaller spray coneangle facilitates easymovement of particles to the fluidized bed. The accuracy of REAmodel in predictingthe single dropletdrying kinetics wasalso explained.
Jin and Chen (2009)
Application of CFD in food industry: Cold storage.
Contours of iso-temperatures in the most sensitive plane of a refrigerated truck (a)
without air ducts (b) with air ducts
Application of CFD in food industry: Pasteurization
a)
Temperature (C) profiles of pasteurisation (85C) process of milk in stationary position of can at (a) 60 s (b) 120 s (c) 240 s and (d) 360 s.
b)
c) d)
Thank you
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