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CFD for Building and Facilities Design
By: Tommy Mello
Co-Founder: Sim Specialists LLC.
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Sim Specialists Ketivsexpert simulation partner
Solve active product development challenges
Build user proficiency
Training
Customized Mentoring
Tommy Mello
Mechanical Engineer
Fluid dynamics concentration
Former engineering lead at BRNI
Company that developed the original Cfdesign technology acquired by Autodesk and known as
Simulation CFD
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Background
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Capital Investment
Resources
Personnel
Hardware
Distraction
Higher priorities and responsibilities
Lack of confidence the technology canDont know how to get started
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Barriers to Entry
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Computational Fluid Dynamics Numerical method to virtually predict fluid flow performance
without the need for physical testing.
What is CFD?
Autodesk Sim Mechanical Autodesk Sim CFDSimulates Solids Fluids ( + solids for thermal)
Calculates Disp, strain, stress, temp,
modal response
Velocity, pressure, density,
temperature
Equations Hookes Law {F}=[k]{x} Navier Stokes (RANS)
Examples
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Navier StokesSoftware solves, not you!
Advection Scheme
Numerical transport
Turbulence models
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Dont Worry
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High level predictions Make assumptions and take liberties
Inspect local regions
Look through output files
Summary File
Fluid Energy Balance
Mass flow balance between inlets & outlets
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What you do
lvRe
tQ
cm p
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Applications
Structural
Electronics
Flow Control
Building / HVAC
Lighting
Heating / Refrig
Heat Exchangers
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Sustainability
Energy Consumption
Data Centers
Human Comfort
Odor Containment
Fume Hoods
Air Curtains
Clean Rooms
Smoke Control
Ducting Design
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AEC Applications
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Simulation ROI CFD Applications Implementation
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Overview
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Processing Plant
Buhlers grain Milling Automation
Trane RTU
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ROI
Capital
Operational
Cost Savings
$22,000 in RTUs$15,625 / year
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RTU OptimizationProcessing Plant
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Thermal Stratification
Extended Ductwork ReturnReduced return Temperatures by 2F
348 kw / 1M sqft.
$0.08/kWH
1,870 cooling hours
Annual savings
$52,000!
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Washington BWI Airport Terminal
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Glass wall / WindowsAbsorption / Transmission
Location, Date, Time
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Solar Load and Glass Wall
Inside OutsideWall
Wall
Abs
orbed
ConvectConvect
Conduction
Max Solar Energy: 910 W/m2
Typical: 150-300
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LibraryInitial Concept
Large atrium
Direct sunlight after noon
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Improve performance?
ROI?
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Louver Library
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Initial Concept Louvers
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Implications
Quantity Reduced Louvers
Temperature 3F
Floor Heat Flux (w/m2) 20%
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Absorption and Reflection
Solar heating occurs on less internal surface area
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Mechanism
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Sustainability
Operating Costs
Simplicity
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Stack Effects
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Buoyancy
Raleigh number (Ra) determine laminar / turbulent regime (similar to Re in forced convection)
Grashof number (Gr) represents the Buoyancy vs. Viscous forces
Prandtl number (Pr) is the ratio of viscous to thermal diffusion rates
Nusselt number (Nu) is the ratio of Convection vs. Conductive heat transfer
Wind effect
Vent location
Chimney design
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2013
Autodesk
Cincinnati Music Hall
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24
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25
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2013
Autodesk
Parking Structure
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Visualize
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1. Use it Active efforts
Proficiency
Exposure
Adoption
Positive Investment
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Historically
2. Loose it Shelf-ware
Collecting Dust
Bad Investment
Why?
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Business initiativesSustainability
Energy Consumption
Thermal Comfort
Customer request
Field Failures
Credibility building
No prototyping
Has to work the first time around
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Active Efforts
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Internal
Software / Hardware
Staff
Expertise
Proficiency with tools
External
Trust
Experience
Combination
Project jump start
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Current Capacity
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Geometry
CAD creation or optimization for simulation
Capture design intent
Knowledge
CFD: assumption implications and validity Turbulence models
Advection scheme
Mesh implications
Software Inputs
Outputs
Caveats
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What Does it Take?
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PartnershipSome or all of project
Project jump start
TrainingFundamentals
Customized mentoring
Experience
Time & repetition
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How?
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Start to finish
Mentoring
Compartmentalized
On demand / as needed
Project Jump Start Optimize geometry for simulation
Provide benchmark
Transfer technology: Empower you to explore design options
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Simulation Resource
Project
CAD
Foundation of Simulation
Capture Design Intent
Analysis
Benchmark
Modifications
Design Solution
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Complete & Turn in your Survey for
a chance to Win a 3DConnexion:
SpacePilot Pro Wireless 3D Mouse
Drawing at 4:30 pm in the
Cerritos Ballroom
OR
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Questions?
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Typical AEC Simulations
Mesh intensiveLarge domains (lobbies, gymnasiums, stadiums) with small
details (ducting, radial diffusers)
Conjugate heat transfer
Usually thermal changes in the air have an impact.
Mixed Convection
Many situations have combined forced convection (air
conditioning) with natural convection (buoyancy effects).
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Fluid Domains for AEC
In CFD, all fluid regions (air, water) must be modeledas a solid volume
2 options . . .
Create volume directly in CAD
Cap-no-go method
Air-tight void in model
Volume created by SimCFD
during launch
Caps used
to seal off
inner void
Caps used
to seal off
inner void
Caps used
to seal off
inner void
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AEC Modeling Options
Setup
Walls, windows
suppressed
Inside Outside
Window
Wall
Wall
Air
Domain
Walls, windows
included
Uwall , Tambient
Uwindow , Tambient
Air
Domain
Uconvection , TambientUconvection , TambientUconvection , Tambient
Conductivity, kConductivity, k
PREFERRED
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Typical U-factors
In CFD, the U-factor is the film coefficient, h
Location U (BTU/hr-ft2-R) U (W/m2-K)
Natural convection 1.76 10.0
Wallsolid brick 0.39 1.00
Wallwood studs, R13
insulation
0.08 0.45
Window, single glass 1.10 6.24
Window, double glass,
air space
0.59 3.36
Door, 1 wood 0.64 3.64
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AEC Thermal Loads to Consider
Convection
Interior Loads:
Humans
Equipment
Lighting
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Along with conducting heat, exterior windows can also let solarenergy into the inner air space.
Easier
Suppress window
Hand calc for heat fluxSolar heat gain coefficient
SGHC x Solar load
Apply heat flux and U-factor
Much HarderModel window
Must know window properties
Set up solar radiation model
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Window Considerations
Inside OutsideWall
Wall
Absorbed
ConvectConvect
Conduction
Max Solar Energy: 910 W/m2
Typical: 150-300
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The Human Factor
Human figures look cool and add a sense
of scale, but added detail = more mesh!Avoid highly detailed figures -------------
Model groups or crowds with a block
Resistance region with total wattage applied
Humans output about 70-100 Watts of thermal energy
9x70 = 630W
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Air material must be set toVariable!
Solver settings
Flow and thermal must be run at
the same time
Remember to set gravity vector!
Advection 2 is preferred.
Setting up Natural Convection
Solver settings
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