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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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