Jim Aswegan Chief Engineer

Transcription

1 Displacement Ventilation Jim Aswegan Chief Engineer

2 Displacement Ventilation Systems Comfort & Contaminate Control DV Concepts & System Benefits Outlet Types and Air Patterns Example l Space Layouts Displacement & LEED 2

3 ASHRAE 2011 Application Ch. 57 Fully Stratified Partially Mixed Fully Mixed Displacement Under Floor Air Distribution G.R.D.

4 Fully Mixed Air Distribution Cold & (Hot) Supply Air F F (85 90 F) High Velocity Supply Outside Occupied Zone Minimizes Temp. Variations in Space Uniform Contaminate Concentration 4

5 Fully Mixed Air Distribution Mixed Air Distribution Mixed Contaminates 5

6 Fully Stratified Air Distribution Cool Air Supply Only 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

7 Fully Stratified Air Distribution 7

8 Displacement Ventilation BASIC CONCEPTS & SYSTEM BENEFITS 8

9 Basic System Concepts Low Energy ( < 0.04 Ps) Air Change Effectiveness (Std. 62.1, Ez = 1.2) Quiet Operation (< 25 NC)

10 Low Energy 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

11 HVAC System Benefits Heat sources outside the stratification layer are not considered in airflow calculations l Lighting load is designed as equipment load, but not as space load Eff t li l d it b t t i Effects cooling load capacity, but not air distribution capacity

12 HVAC System Benefits Use 100% outside air overnight to cool Reduced chiller capacity Can be considered a thermal energy storage Can be considered a thermal energy storage system qualifying the owner for utility rebates

13 Low Energy Lower horsepower fans 004in 0.04 in. pressure is required for proper diffuser performance Results in lower horsepower fans required = Fan Energy egysavings

14 Improved Ventilation ASHRAE Standard d 62.1 Ventilation for Acceptable Indoor Air Quality Zone Air Distribution Effectiveness, E z Overhead Cooling System = 1.0 Displacement l t Ventilation = % Less Fresh Air Required

15 Return Air Outlet located at ceiling level Allows heat tfrom ceiling lights to be returned before it is able to mix with occupied zone Reduced supply volume Reduced supply volume means higher return temperatures

16 Humidity Issues 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 f l d f d h df If 55 o F supply air is used for dehumidification, return air can be mixed with supply air to achieve 65 o F air

17 Perimeter Heating 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 Rdi Radiant panels Dual Chamber Diffuser 17

18 Dual Chamber Diffuser Dual chamber diffuser Dual chamber plenum Displacement cooling Mixed-air heating Actuated diverter (24V) Displacement diffuser cooling Linear diffuser heating 18

19 Application Examples Good applications Room height > 9.0 ft Open Plan Offices Meeting Rooms Casinos Restaurants Theaters, & Auditoriums Schools & Universities 19

20 Displacement Ventilation Advantages Smaller cooling power for desired room temperature in the occupied area Improved air quality in occupied area Longer periods of free cooling 20

21 Application Examples Poor Applications Room height < 9 ft Surplus heat tis the main problem not air quality In combination with mixing systems Office/rooms with cubicles Spaces with heavy contaminants 21

22 Displacement Ventilation Disadvantagesg 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 ft t 2 Cannot heat with displacement ventilation 22

23 Thermal Comfort ASHRAE Standard 55 Thermal Environmental Conditions for Human Occupancy Maximum recommended T hf = 5.4 F Avoid drafts by keeping T es < 36 F

24 Temperature Gradient Ceiling Height % Rule is applied 62 F 72 F 82 F 10 F 10 F (Displacement ventilation, REHVA)

25 Temperature Gradient Ceiling Height > 14 33% Rule 33% 67% 65 F 72 F 86 F 7 F 14 F (Displacement ventilation, REHVA)

26 Displacement Ventilation TYPES OF OUTLETS & DISTRIBUTION PATTERNS 26

27 Adjacent Zone 27

28 Discharge Air Patterns 28

29 Standard Air Patterns Adjusted Air Patterns 29

30 Rectangular Displacement Diffusers Mounts in wall 1 way pattern 30

31 Displacement Diffusers Rectangular Rectangular In wall, flush or floor mount 31

32 Displacement Diffusers Rectangular 3 Way Rectangular In wall, flush or floor mount 3 way pattern 32

33 Displacement Diffusers Rectangular Curved Face Flush or floor mount 3 way pattern 33

34 Displacement Diffusers Rectangular Stair Riser Steps, Stair Risers applications Great for auditoriums, concert, arena s, and lecture halls 34

35 Displacement Diffusers Circular Column l or floor mount 360º discharge 35

36 Displacement Diffusers Semi Circular 180º Sidewall or column applications 180º pattern 36

37 Displacement Diffusers U shaped Semi circular i i l w straight ih sides 3 way pattern 37

38 Displacement Diffusers Corner w/ Curved Face Corner mount applications i 2 way pattern 38

39 Displacement Diffusers Corner/Flat Face Corner mount applications 2 way pattern 39

40 Displacement Ventilation EXAMPLE SPACE LAYOUTS 40

41 Private Perimeter Office Perimeter Wall 41

42 Open Plan Interior Office 42

43 Interior Break Room Round Outlets 43

44 Perimeter Conference Room Outside Wall 44

45 Elementary School Classroom Perimeter Wall 45

46 ASHRAE Standards for LEED ASHRAE S 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 : Thermal Comfort: Design IEQ Credit 7.2: Thermal Comfort: Verification

47 Displacement & LEED Optimize Energy Performance (EAc1) Minimum IAQ Performance (EQp1) Increased d Ventilation i (Q2) (EQc2) Thermal Comfort: Design (EQc7.1)

48 Displacement Ventilation & LEED Minimum Energy Performance: EAp2 Optimize Energy Performance: EAc1 Minimum Indoor Air Quality Performance: IEQ p1 Increased Ventilation: IEQc2 Thermal Comfort Design: IEQc7.1 48

49 Minimum IAQ Performance (EQp1) Minimum IAQ per ASHRAE EQ Q Prereq 1 Required

50 Increased Ventilation (EQc2) Increase breathing zone outdoor air ventilation rates to all occupied spaces by at least 30% above the minimum rates required by ASHRAE Standard 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

51 Thermal Comfort (EQc7) Design Comply with ASHRAE Standard Submit Narrative detailing established comfort criteria per ASHRAE Standard , the desired quality and occupant satisfactionwithbuildingperformance performance, and supporting documentation showing the system design meetsthese these criteria EQ Credit Point

52 Publications 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)

53 Thank you! Questions? 53