DisplacementDisplacement Jim Aswegan VentilationVentilation Chief Engineer DisplacementDisplacement VentilationVentilation SystemsSystems

Comfort & Contaminate Control

DV Concepts & System Benefits

Outlet Types and Air Patterns

Example Space Layouts Displacement & LEED

2 ASHRAEASHRAE –– 20112011 ApplicationApplication Ch.Ch. 5757

Fully Stratified Partially Mixed Fully Mixed

Displacement Under Floor Air Distribution G.R.D. FullyFully MixedMixed AirAir DistributionDistribution

Cold & (Hot) Supply Air 48‐58 °F(85‐90 °F)

High Velocity Supply Outside Occupied Zone

Minimizes Temp. Variations in Space

Uniform Contaminate Concentration

4 FullyFully MixedMixed AirAir DistributionDistribution

Mixed Air Distribution Mixed Contaminates

5 FullyFully StratifiedStratified AirAir DistributionDistribution

Cool Air Supply Only 60 ° ‐ 68 °

Air is Supplied Horizontally across the Floor at Low Velocity (< 70 fpm) Temperature Stratification from Floor to Ceiling (Return)

Contaminate Concentration reduced in Occupied Zone

6 FullyFully StratifiedStratified AirAir DistributionDistribution

7 Displacement Ventilation

BASICBASIC CONCEPTSCONCEPTS && SYSTEMSYSTEM BENEFITSBENEFITS

8 BasicBasic SystemSystem ConceptsConcepts

 Low Energy – ( < 0.04 Ps)

 Air Change Effectiveness – (Std. 62.1, Ez = 1.2)

 Quiet Operation – (< 25 NC) LowLow EnergyEnergy

Higher equipment efficiency

– Uses warmer supply air • 65°F compared to 55°F

– Energy consumption is often reduced by raising discharge temperature – Extended Economizer Cycle HVACHVAC SystemSystem BenefitsBenefits

Heat sources outside the stratification layer are not considered in airflow calculations – Lighting load is designed as “equipment load”, but not as “space load”

– Effects cooling load capacity, but not air distribution capacity HVACHVAC SystemSystem BenefitsBenefits

Use 100% outside air overnight to cool

– Reduced chiller capacity

– Can be considered a thermal energy storage system qualifying the owner for utility rebates LowLow EnergyEnergy

Lower horsepower fans

– 0.04 in. pressure is required for proper diffuser performance

– Results in lower horsepower fans required = Fan Energy Savings ImprovedImproved VentilationVentilation

ASHRAE Standard 62.1 ‐ Ventilation for Acceptable Indoor Air Quality

Zone Air Distribution Effectiveness, Ez Overhead Cooling System = 1.0 Displacement Ventilation = 1.2 16.7% Less Fresh Air Required ReturnReturn AirAir

 Outlet located at ceiling level

 Allows heat from ceiling lights to be returned before it is able to mix with occupied zone

 Reduced supply volume means higher return temperatures HumidityHumidity IssuesIssues

 A potential problem with warmer supply air temperatures is higher humidity

 Supply system must reduce relative humidity to less than 60% to meet IAQ concerns – Condenser water reheat, run‐around coils, or face & bypass

– Use of a separate system to dry outside air or the use of desiccant dehumidification  If 55oF supply air is used for dehumidification, return air can be mixed with supply air to achieve 65oF air PerimeterPerimeter HeatingHeating

Perimeter heating can not be accomplished with traditional displacement ventilation

Separate system required in most applications: – UFAD perimeter system – Perimeter fan powered systems – Ducting of hot or reheated air – Baseboard Radiation – Radiant panels – Dual Chamber Diffuser 17 DualDual ChamberChamber DiffuserDiffuser

Dual chamber plenum Dual chamber diffuser  Displacement cooling  Mixed-air heating  Actuated diverter (24V)

Displacement diffuser – cooling

Linear diffuser – heating

18 ApplicationApplication ExamplesExamples

 Good applications – Room height > 9.0 ft – Open Plan Offices – Meeting Rooms – Casinos – Restaurants – Theaters, & Auditoriums – Schools & Universities

19 DisplacementDisplacement VentilationVentilation

 Advantages – Smaller cooling power for desired room temperature in the occupied area

– Improved air quality in occupied area

– Longer periods of free cooling

20 ApplicationApplication ExamplesExamples

 Poor Applications – Room height < 9 ft – Surplus heat is the main problem –not air quality – In combination with mixing systems – Office/rooms with cubicles – Spaces with heavy contaminants

21 DisplacementDisplacement VentilationVentilation

Disadvantages – Risk of draft due to placement of the diffusers – Wall mounted devices often occupy large wall areas

– Stratified air becomes uncomfortable when cooling load exceeds ~30 Btu/hr‐ft2 – Cannot heat with displacement ventilation

22 ThermalThermal ComfortComfort

 ASHRAE Standard 55 – Thermal Environmental Conditions for Human Occupancy

 Maximum recommended ∆Thf = 5.4°F  Avoid drafts by keeping ∆Tes < 36°F TemperatureTemperature GradientGradient

Ceiling Height 9’‐14’

50% Rule is applied

62°F –72°F –82°F

10°F ‐ 10°F (Displacement ventilation, REHVA) TemperatureTemperature GradientGradient

 Ceiling Height > 14’

 33% Rule 33% 67%

 65°F –72°F –86°F

7°F ‐ 14°F

(Displacement ventilation, REHVA) Displacement Ventilation TYPESTYPES OFOF OUTLETSOUTLETS && DISTRIBUTIONDISTRIBUTION PATTERNSPATTERNS

26 AdjacentAdjacent ZoneZone

27 DischargeDischarge AirAir PatternsPatterns

28 StandardStandard AirAir PatternsPatterns‐‐ AdjustedAdjusted AirAir PatternsPatterns

29 Displacement Ventilation Sizes and Shapes AIRAIR PATTERNSPATTERNS DisplacementDisplacement DiffusersDiffusers Rectangular

Mounts in wall

1–way pattern

31 DisplacementDisplacement DiffusersDiffusers

Rectangular

Rectangular

In wall, flush or floor mount

32 DisplacementDisplacement DiffusersDiffusers

Rectangular 3‐Way Rectangular

In wall, flush or floor mount

3–way pattern

33 DisplacementDisplacement DiffusersDiffusers

Rectangular – Curved Face Flush or floor mount 3–way pattern

34 DisplacementDisplacement DiffusersDiffusers

Rectangular – “Stair Riser”

. Steps, Stair Risers applications

.Great for auditoriums, concert, arena’s, and lecture halls

35 DisplacementDisplacement DiffusersDiffusers

Circular

Column or floor mount

360º discharge

36 DisplacementDisplacement DiffusersDiffusers

Semi‐Circular 180º Sidewall or column applications

180º pattern

37 DisplacementDisplacement DiffusersDiffusers

U – shaped

Semi‐circular w straight sides

3–way pattern

38 DisplacementDisplacement DiffusersDiffusers

Corner w/ Curved Face

Corner mount applications

2–way pattern

39 DisplacementDisplacement DiffusersDiffusers

Corner/Flat Face

Corner mount applications

2–way pattern

40 Displacement Ventilation EXAMPLEEXAMPLE SPACESPACE LAYOUTSLAYOUTS

41 PrivatePrivate PerimeterPerimeter OfficeOffice

Perimeter Wall

42 OpenOpen PlanPlan InteriorInterior OfficeOffice

43 InteriorInterior BreakBreak RoomRoom

Round Outlets

44 PerimeterPerimeter ConferenceConference RoomRoom

Outside Wall

45 ElementaryElementary SchoolSchool ClassroomClassroom

Perimeter Wall

46 ASHRAEASHRAE StandardsStandards forfor LEEDLEED

ASHRAE 62.1 – IEQ Prerequisite 1: Minimum IAQ Performance – IEQ Credit 1: Outdoor Air Delivery Monitoring – IEQ Credit 2: Increased Ventilation – IEQ Credit 6.2: Controllability of Systems: Thermal Comfort (for naturally ventilated spaces) ASHRAE Standard 55 – IEQ Credit 6.2: Controllability of Systems: Thermal Comfort – IEQ Credit 7.1: Thermal Comfort: Design – IEQ Credit 7.2: Thermal Comfort: Verification DisplacementDisplacement && LEEDLEED

Optimize Energy Performance (EAc1) Minimum IAQ Performance (EQp1) Increased Ventilation (EQc2) Thermal Comfort: Design (EQc7.1) DisplacementDisplacement VentilationVentilation && LEEDLEED

 Minimum Energy Performance: EAp2  Optimize Energy Performance: EAc1  Minimum Indoor Air Quality Performance: IEQ p1  Increased Ventilation: IEQc2  Thermal Comfort Design: IEQc7.1

49 MinimumMinimum IAQIAQ PerformancePerformance (EQp1)(EQp1)

Minimum IAQ per ASHRAE 62.1‐2007

EQ Prereq 1 – Required IncreasedIncreased VentilationVentilation (EQc2)(EQc2)

Increase breathing zone outdoor air ventilation rates to all occupied spaces by at least 30% above the minimum rates required by ASHRAE Standard 62.1‐2007 as determined by EQ Prereq. 1 Submit – Narrative describing the project’s ventilation system, including fresh air intake volume for each zone and confirmation that outdoor air exceeds ASHRAE 62.1 by 30% EQ Credit 2 ‐ 1 Point ThermalThermal ComfortComfort (EQc7)(EQc7) Design

Comply with ASHRAE Standard 55‐2004 Submit ‐ Narrative detailing established comfort criteria per ASHRAE Standard 55‐ 2004, the desired quality and occupant satisfaction with building performance, and supporting documentation showing the system design meets these criteria

EQ Credit 7.1 ‐ 1 Point PublicationsPublications

 HVAC Applications Handbook, Chapter 57 (ASHRAE, 2011)  Fundamentals Handbook, Chapter 20 (ASHRAE, 2009)  System Performance Evaluation and Guidelines for Displacement Ventilation (ASHRAE, 2003)  Displacement Ventilation in Non‐Industrial Premises (REHVA, 2002) ThankThank you!you!

Questions?

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