11/8/2018 Heapy Engineering is a Registered Provider with The - - PDF document

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Heapy Engineering is a Registered Provider with The American Institute

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Architects Continuing Education Systems. Credit earned on completion of this program will be reported to CES Records for AIA members. Certificates of Competition for non-AIA member are available on request. This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any materials, methods, and services will be addressed at the conclusion of this presentation.

BRIEF OVERVIEW

This presentation will provide an overview of computational fluid dynamics use in the built environment. CFD can provide a valuable design tool, allowing architectural and engineering flexibility to complex problems and building design. CFD can also provide noticeable cost savings, allowing evaluation of systems or concepts that previously were un-testable or required significant man-hours to complete. Included in the presentation are overviews of some of the various software packages that are available to the A/E for use in building and environmental design. The software applications shown will include those used for architectural assistance, mechanical design, fire protection design (smoke control), and data center thermal control applications.

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LEARNING OBJECTIVES

• Attendees will learn how computational fluid dynamics can be

utilized in the built environment to shape building system and design;

• Attendees will understand the various applications that can be

utilized during design;

• Attendees will understand how CFD contributes to performance-

based design;

• Attendees will recognize how CFD can contribute to an overall

design and construction cost savings.

SPEAKER BIO

Matt Sciarretti PE, CPD, CFPS, LEED AP BD+C Principal, Tech Manager – FP & Plumbing Daniel Lampke PE, MS: FPE Senior Fire Protection Engineer

• 1. Background
• 2. Benefits of CFD
• 3. Applications
• A. Wind Modeling
• B. Smoke Control/Life Safety Analysis
• C. Thermal Comfort
• D. Data Center Modeling
• 4. Cost Savings Through CFD

PRESENTATION OUTLINE

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BACKGROUND – WHAT IS CFD?

• Computational Fluid Dynamics
• Combination of fluid mechanics, iterative numerical

analysis, and computer science applications

• Uses algorithms to calculate motion and effects of different

fluids in a space with predefined conditions.

• Allows early and accurate prediction of device/system

performance.

• Reduces need for analytical studies / prototyping.
• Validates performance-based design.
• Allows rapid iterative development/evaluation.

WHAT CAN WE DO WITH CFD?

We can now project the interaction/effects of fluid motion!

• Fluids are everywhere – Air, water, fuels.
• Can follow particles suspended in fluids too –

smoke particles, chemical concentrations, etc. The following slides demonstrate capabilities of some software, including: 1. Smoke control/exhaust in an irregular atria; 2. Exterior wind modeling; 3. Thermal controls & adjustments in a multiuse room; 4. Data center airflow & thermal predictions.

HOW CAN CFD ASSIST THE DESIGN PROCESS?

• CFD Modeling can be used to predict real-world conditions and aid in

design decisions.

• Forecast various design changes.
• Allows design professionals to provide a tailored solution or perform rapid

iterative design.

• Allows A/E to be more creative with design.
• Approach can be validated thoroughly.
• Visual representation of results.
• Visuals can be very important during approvals/variance meetings.

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MANY MORE USES!

Not an exhaustive list by any means – we cover 4 ways to use CFD modeling, but there are many other uses including:

• Airflows around vehicle & equipment heat stress;
• Design of plumbing fixtures / fluid mixing;
• Modeling Engine ports – thermal effects & thrust;
• Chemical dispersal models;
• Clean room simulations;

…and many others!

Exterior Wind Modeling

And Plume Injections

WIND MODELING

• CFD involves the modeling of particles.
• What can also be represented as movement of

particles? Wind!

• Air/gases can be modeled in CFD programs, with velocity added to simulate

air movement.

• Uses for exterior wind modeling include:
• 1. Model the flow of air contaminants away from the building.
• 2. Analyze the effects of wind on an external sitting/eating area.
• 3. Investigate stresses on building elements during extreme conditions.

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WIND MODELING: EXHAUST AIRFLOW

Evaluation of wind flow patterns against building geometry to determine if building equipment exhaust will be sucked in through fresh air intakes.

WIND MODELING: CONTAMINANT DISPERSION

WIND MODELING: OCCUPANT COMFORT

• Wind can also be a factor for occupant

comfort and space utilization.

• Case Study - Wind Effects on Exterior

Sitting Area.

• Problem: Hospital’s rear courtyard cafeteria

area reporting high speed turbulent winds.

• Wind swirls were reportedly lifting

mulch 3 stories to roof of building and toppling exterior metal trash cans.

• Space was unusable for cafeteria.
• Building was recreated in CFD and analyzed

against the wind conditions of the various seasons.

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WIND MODELING: VERIFICATION OF EXISTING CONDITIONS

• Courtyard wind vortex effect

replicated in model.

• Design was verified against known

conditions to ensure model could provide a realistic analysis.

• Once a baseline was established,

then iterative design could progress.

WIND MODELING: ITERATION & FINAL DESIGN

Able to run 10 different scenarios.

• 5 different protection

schemes

• 2 different material types

Final Design – Sloping Solid Roof

• Low wind speeds
• No vertical wind

movement

WIND MODEL: SAVINGS

Using CFD to analyze the previous building wind model resulted in an effective solution, developed with minimal man-hours and validated via software. If the solution was left to general contracting, there would have been greater waste in design iteration. The first initial design evaluations focused on

• wner’s suggested solutions, including a horizontal

wind barrier (fence). CFD proved such a “solution” would have been

• ineffective. Use of software evaluation led to the

correct solution quickly, and least overall cost.

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Smoke Control

ATRIUMS

• Any atrium connecting 3 or more stories requires

a smoke control system.

• The OBC & NFPA 92 outline calculation

procedures for a simplistic, rectangular atrium.

• Very prescriptive requirements.
• Problem: most atriums are not rectangular.
• Angled geometry, hanging design elements

(artwork), irregular ceiling patterns: all affect performance of exhaust system.

• Algebraic calculations, due to various

assumptions, often result in excessive exhaust & make-up air.

• How do we account for this and design an

effective system? CFD Modeling.

PERFORMANCE-BASED DESIGN IN ATRIUMS

• CFD Modeling can account for all irregular geometries, exhaust system modifications, and

different fire locations to fully evaluate the prescriptive design.

• Can also be used for more performance-based smoke exhaust strategies.
• Can calculate time-to-egress of occupants from the building, then demonstrate smoke layer

descent versus occupied floor evacuation.

• Compared to prescriptive design, CFD can potentially reduce equipment sizes while

maintaining the same level of life safety.

• Recognized by OBC and NFPA 92 as a viable and approved alternative to prescriptive

design.

• Validation tool – may satisfy fire prevention personnel without performing ineffective

testing.

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SMOKE CONTROL – EXAMPLE

EXISTING STRUCTURE WITH NEW 3 STORY ATRIUM

3D Perspective Plan View

SMOKE CONTROL – RESULTS SMOKE CONTROL - RESULTS

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SMOKE CONTROL: SAVINGS

This atrium was very irregularly shaped, which did not fit general prescriptive code analysis. A multi-part finite element analysis would have taken an exorbitant amount of time and prone to human error. CFD could be grouped with occupant egress calculations to validate life safety while the smoke was exhaust at the roof. Use of CFD reduced the prescriptive- calculated exhaust fan size by 35% (reducing generator size too!)

ADDITIONAL EXAMPLE - SMOKE CONTROL SAVINGS

• Another project involved the analysis of occupant

egress capability within a lengthy, 4-story atrium.

• System was functional and tested regularly.
• However, due to atrium modifications, the exhaust

system needed to be validated…and if not, upgraded!

• Cost to upgrade ~ $4,000,000 – exhaust and makeup

air fans, fire alarm system upgrades, generator replacement, etc.

• Use of CFD with egress software validated the

effectiveness of the currently installed smoke control system in maintaining life safety throughout entire building egress.

Thermal conditioning

Using CFD to predict the performance of passive conditioning systems

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THERMAL CONDITIONING

• CFD is perfect for predicting thermal comfort within a space.
• Can model HVAC system supply & exhaust.
• Temperature and airflow velocity.
• Determine what areas may be experiencing incorrect thermal control.
• Useful for space renovations/occupancy use changes.
• Important use – Displacement ventilation!
• Example: thermal comfort in a newly-enclosed interior atrium.

AIR DISTRIBUTION – MODEL SETUP

SET UP

• Displacement Ventilation had diffusers at floor level – the principal occupied space.
• Had 6 grille-type wall supply diffusers and 4 trashcan-style diffusers – all which are replicated in CFD.

Restrictor Orifices Colored faceplates represent a diffuser at a certain % open

RESULTS - THERMAL

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RESULTS – OCCUPANT LOAD (COOLING) THERMAL CONDITIONING: SAVINGS

Assembly space was a previously-open courtyard, which was capped by a glass roof and reclaimed for event space. Surrounding building was existing, and therefore running ductwork through walls would have been cost prohibitive. Only accessible portion was through floor – typical HVAC would not have operated properly. CFD validated the use of quiet displacement ventilation methods to condition the space, saving the building from major renovations. Total Annual Savings: $8,000, and a major savings in existing building space as additional AHU and large ductwork was not required.

Data Center Modeling

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DATA CENTER MODELING

• Speed
• Quicker model construction, iterative design.
• User friendly
• Fewer man-hours spend developing/revising a

model.

• Less costly (theoretically) – labor & software.
• Next slides will focus on the use of “Coolsim”,

which is a data-center-specific program. WHY CHOOSE A SPECIFIC PROGRAM? WHY CHOOSE A GENERAL PROGRAM?

• Flexibility.
• More powerful.
• Components.
• Meshes.
• Boundary Conditions.
• Big growth in the business market.
• Multiple programs have been created in last 4 years to solely

develop Data center CFD models.

DATA CENTER PREDICTIONS USING CFD

Uses:

• In-room airflow design;
• CRAC Failure analysis;
• Evaluation of rack

chimney efficiency gains;

• In-rack cooling load

balancing and airflow design;

• Any many more!

Benefits:

• Decreased energy

usage;

• Reduction in cooling

equipment and equipment footprints;

• Rack/CRAC

arrangements;

• Future iterative

evaluations.

ADVANCED BUILD PROCESSES

• Due to the focused application of dedicated

CFD programs, Data center builds can be done very rapidly, with all the essential details replicated.

• Racks
• Complete and partial rack fit-outs.
• CRACs
• Large in-room and small in-row units.
• Ductwork
• Supply/return, combinations.
• Aisle containment
• PDU’s
• Structural elements

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DATA CENTER – RESULTS

Inlet Temperature Displays

Simplified ASHRAE Thermal Ranges Room Thermal slices

DATA CENTER – RESULTS

CRAC and Rack Airflows

DATA CENTER EXAMPLES

Baffles within a cabinet affecting airflow Effect of cold aisle containment Without With

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DATA CENTER EXAMPLES

CRAC Failure (Note the temperature scale!) Airflow – effect of a ceiling return In-room return Ceiling return

THERMAL CONDITIONING: SAVINGS

Many factors influence cost savings in a data center – chilled water, controls, motors, heat recovery, etc. CFD can evaluate these multiple factors, allowing rapid iteration and decision making across a variety of arrangements. Example of a recent completed project included evaluation of factors above…total rate of return for combined above 15%. Addition of Cold Aisle Containment & VFD air condition resulted in savings of $30,000/year.

SUMMARY

• CFD Modeling allows us to perform additional analysis in the early

stages of the project.

• Can help reduce construction or occupancy related issues.
• Can validate design decisions.
• Can aid in performance-based design.
• Flexible, multiuse tool.
• Key component in iterative design.
• Can provide significant design and construction cost savings.
• Valuable addition to any design project.

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MATT SCIARRETTI Heapy Engineering 937-224-0861 sciarretti@heapy.com DAN LAMPKE Heapy Engineering 937-224-0861 dhlampke@heapy.com