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ASHRAE‐Chicago
Air Distribution Selection Basics
           June 8, 2010
ASHRAE ‐ Air Distribution Systems
              2007 Applications Handbook, Ch. 56
            Fully Stratified           ...
ASHRAE Standard 55‐2004 
Occupant Comfort Goal
Dry Bulb = 73-77 °F.
Relative Humidity = 25-60%.
Local Velocities =
    ...
Occupied Zone for Comfort
                                                Mixed Air Outlet

     Ceiling



      1'
6'   ...
Fully Mixed Air Distribution
Air Patterns
Mapping Room Air Motion
Vertical Projection
ADPI
Perimeter Heating


      ...
Air Flow Patterns
High Sidewall – No Ceiling
   Horizontal Pattern
     Deflected (less drop)
     Spread (shorter thr...
Supply Sidewall Grilles
Adjustable:
     Horizontal
     (spread)

     Vertical
     (deflection)

Duct Mounting
   Ve...
Return Sidewall Grilles
Return
   Non Adjustable

   Zero Degree Deflection

   30-45 Deflection

   Other




      ...
Air Flow Patterns
Radial Air Pattern
   Shorter Throw
   More Induction




                      © 2010. All rights re...
Round Pattern Diffusers




                © 2010. All rights reserved
Air Flow Patterns
Cross Flow
   Longer Throw

   Increased Drop




                     © 2010. All rights reserved
Cross Pattern Diffusers




                 © 2010. All rights reserved
Linear with Plenum or T‐Bar Diffusers
 With Spreader                           W/O Spreader

    Linear
    Plenum




 ...
Linear‐Plenum Slot Diffusers




                © 2010. All rights reserved
Air Flow Patterns
Radial Pattern - Exposed Duct




                  © 2010. All rights reserved
Air Flow Patterns
Cross Pattern - Exposed Duct




                  © 2010. All rights reserved
POOR PATTERN EXAMPLE
             POORLY ADJUSTED
                DIFFUSER




THERMOSTAT




              © 2010. All ri...
GOOD PATTERN EXAMPLE
             PROPERLY ADJUSTED
             DIFFUSER




THERMOSTAT




              © 2010. All rig...
Mapping Room Air Motion
5-step approach
   Primary air
   Total air
   Convection currents
   Room intake
   Room ai...
Step 1: Identify the Primary Air
Primary Air - mixture                      Primary air patterns are
  of air supplied t...
Step 2: Identify the Total Air
 Total Air - mixture of                       Temperature difference
   primary air and r...
Step 3: Identify Natural 
Convection Currents
 Natural Convection                      Affects room air motion
  Current...
Step 4: Identify the Return Intake
 Return Intake - return                   Even natural convection
  intake affects on...
Step 5: Identify the Room Air
 Room Air Diagram is complete                Most uniform air motion is
  when remaining r...
Mapping Throw




                © 2010. All rights reserved
Mapping Throw

                Cooling




                © 2010. All rights reserved
Estimating Downward Projection
 Chart provides
  vertical throw of a
  free jet to 50 fpm for
  heating and cooling
  wit...
ADPI & Comfort
Air Diffusion Performance Index
Statistically related the space conditions of local
 or transversed tempe...
ADPI
The grey area
 represents
 -3<= <= +2
You can vary
 temperature
 or velocity to
 maintain comfort
15 fpm = 1 °F
...
Throw vs. Characteristic Length




                © 2010. All rights reserved
ADPI Selection Illustration


                                       Point A




      ADPI      Min                  80 A...
Recommended ADPI Ranges for Outlets
       Outlet          T50/L      Range       Calculated         T50 & L    Data

Side...
ASHRAE Standard 62.1 Table 6.2
        Ventilation Air Ez Factor
Ceiling supply of cool air                      1.0
Cei...
Typical Perimeter Solution
 50/50 throw pattern is
  the best compromise for
  both heating and cooling
 Half of the air...
Auto Changeover Diffuser Solution
                                                          Diffuser



             Cooli...
Auto Changeover Diffuser
 Vertical Pattern For
  Heating
 Horizontal Pattern For
  Cooling
 30% Increase In Energy
  Ef...
Sills & Soffits on Perimeter
 Soffits cause air to turn                                 Soffit
  up prematurely
    Aim ...
Air Distribution, Partition Effects




            © 2010. All rights reserved
Partially Mixed Air Distribution
UFAD – Interior Zone
Perimeter with Series Fan Terminal
Perimeter with Plenum VAV Cool...
Underfloor Air Distribution (UFAD)


                                              Stratified
                            ...
Round Access Floor Diffuser
High induction air flow pattern
Occupant adjustable damper
   Actuated version available

...
Interior Applications
Use Conventional Components…
   Round (Swirl) Diffusers
   Rectangular Diffusers

In Conventiona...
Series Fan Terminal for Perimeter
Used in perimeter and conference rooms
   Any room with varying loads
10 ½”, and 14” ...
Typical Perimeter Installation
Low horsepower fan powered terminal unit
 ducted to rectangular floor diffuser plenums



...
Plenums 
Plenum sizes vary
   8” x 16”
   10” x 10”
   12” x 12”


Cores are available in multi-piece
   2-way or 4 ...
ECM Motor
Electronically Commutated Motor




                  © 2010. All rights reserved
ECM Motor
Brushless, DC motor
Converts AC to DC for motor
Ultra high efficiency motor
   Efficiencies of up to 70% acr...
Energy Savings
350 watts savings = .350 kW

250 days/year x 12 hours/day
 = 3000 operating hours/year

.350 kW x 3000 h...
PWM 
The ECM motor is controlled by a PWM (Pulse
 Width Modulated) signal
Voltage pulses over a specific time period
Vo...
Additional ECM Benefits
Soft start
  Motors are set to start up slowly
No brushes
  No noise associated with brushes
 ...
Linear Perimeter System
 (Variable Air Volume)

 (Water Heat)

 (SCR Electric Heat)

 (Return)



                    ...
Perimeter Linear Diffuser Solution




                 © 2010. All rights reserved
Transverse Apertures

      © 2010. All rights reserved
Transverse Apertures

      © 2010. All rights reserved
Transverse Apertures

      © 2010. All rights reserved
Perimeter Smoke Demo Video




              © 2010. All rights reserved
Interior Zone VAV Cooling




     Conference                                 Waiting Area


                  © 2010. All...
Underfloor  System Christman




                                             Linear Heat
                                ...
Fin tube application




                © 2010. All rights reserved
Fully Stratified Air Systems
Energy & Comfort Optimization (ECO)
Basic system concepts
Displacement diffusers




     ...
DV‐ Basic Concepts




                                                             Supply Air
                           ...
Displacement Ventilation Applications
Good application
   Room height > 9.5 ft
   Open Plan Offices, Classrooms, & Meet...
Displacement Ventilation Applications
Poor application
   Room height < 8 ft
   Surplus heat is the main problem – not ...
System Equipment
Higher equipment efficiency
  Uses warmer supply air
     65°F compared to 55°F
  Energy consumption ...
System Equipment
Lower horsepower fans
  0.04 in. pressure is required for proper
   diffuser performance

  Results in...
HVAC System Benefits
Heat sources outside the
 stratification layer are not
 considered in airflow calculations
   Light...
Perimeter Heating
Perimeter heating cannot be
 accomplished with the displacement
 ventilation system

Separate system i...
Return Air
Located at ceiling

Allows heat from ceiling light to be
 returned before it is able to mix with
 occupied zo...
Return Air
If 55oF supply air is used for
 humidity reasons, return air can be
 mixed with plenum air to achieve
 65oF ai...
Temperature Gradient
ASHRAE Standard 55:
   Occupied Zone
   < 5.4°F

Risk of draft increases
 if ∆t > 36°F between
 s...
Temperature Gradient
Ceiling Height 9’-14’

50% Rule is applied

62°F – 72°F – 82°F
   10°F    -   10°F
               ...
Temperature Gradient
33% Rule for > 14’
 room heights
                                              33%   67%

64°F – 72...
Adjacent zone
Discharge
 Velocity < 80 fpm
Area where air
 velocity exceeds
 50 fpm
Occupants
 should not be
 stationed...
Comfort with Adjustable Air Patterns


  Standard adjacent zone from
   factory




  Modified adjacent zone after
   ad...
Comfort Air Distribution
The ASHRAE 2009 Fundamentals handbook,
 Chapter 20, 2007 Applications handbook Chapter
 56, and ...
Questions?
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10 air distribution basics

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10 air distribution basics

  1. 1. ASHRAE‐Chicago Air Distribution Selection Basics June 8, 2010
  2. 2. ASHRAE ‐ Air Distribution Systems 2007 Applications Handbook, Ch. 56 Fully Stratified Partially Mixed Fully Mixed Upper Zone Upper Zone Upper Zone height varies Fully Mixed Elevation Elevation Elevation Elevation Lower Zone Lower Zone Lower Zone Local Temp. Local Temp. Local Temp. Local Temp. CO2 Concentration CO2 Concentration CO2 Concentration CO2 Concentration Partially Mixed Room Air Distribution Systems Displacement Under Floor Air Distribution G.R.D. © 2010. All rights reserved
  3. 3. ASHRAE Standard 55‐2004  Occupant Comfort Goal Dry Bulb = 73-77 °F. Relative Humidity = 25-60%. Local Velocities = Heating < 30 fpm. Cooling < 50 fpm. Clo. Rate 0.5 - 1.1 Met. Rates 1.0 - 2.0 Floor level to 66”; < 5.4 °F (3 °C) Occupied Zone: Floor to 6’0”; except: (Clear, Near, Adjacent) Zone. © 2010. All rights reserved
  4. 4. Occupied Zone for Comfort Mixed Air Outlet Ceiling 1' 6' F Occupied Zone Floor Underfloor Plenum D.V. UFAD Outlet © 2010. All rights reserved
  5. 5. Fully Mixed Air Distribution Air Patterns Mapping Room Air Motion Vertical Projection ADPI Perimeter Heating © 2010. All rights reserved
  6. 6. Air Flow Patterns High Sidewall – No Ceiling  Horizontal Pattern  Deflected (less drop)  Spread (shorter throw) High Sidewall with Ceiling  Longer throw with less drop High Sidewall near Ceiling  Deflect up for longer throw/less drop © 2010. All rights reserved
  7. 7. Supply Sidewall Grilles Adjustable: Horizontal (spread) Vertical (deflection) Duct Mounting  Velocity & Pressure  Air Patterns © 2010. All rights reserved
  8. 8. Return Sidewall Grilles Return  Non Adjustable  Zero Degree Deflection  30-45 Deflection  Other © 2010. All rights reserved
  9. 9. Air Flow Patterns Radial Air Pattern  Shorter Throw  More Induction © 2010. All rights reserved
  10. 10. Round Pattern Diffusers © 2010. All rights reserved
  11. 11. Air Flow Patterns Cross Flow  Longer Throw  Increased Drop © 2010. All rights reserved
  12. 12. Cross Pattern Diffusers © 2010. All rights reserved
  13. 13. Linear with Plenum or T‐Bar Diffusers  With Spreader  W/O Spreader Linear Plenum With Without Spread Spread © 2010. All rights reserved
  14. 14. Linear‐Plenum Slot Diffusers © 2010. All rights reserved
  15. 15. Air Flow Patterns Radial Pattern - Exposed Duct © 2010. All rights reserved
  16. 16. Air Flow Patterns Cross Pattern - Exposed Duct © 2010. All rights reserved
  17. 17. POOR PATTERN EXAMPLE POORLY ADJUSTED DIFFUSER THERMOSTAT © 2010. All rights reserved
  18. 18. GOOD PATTERN EXAMPLE PROPERLY ADJUSTED DIFFUSER THERMOSTAT © 2010. All rights reserved
  19. 19. Mapping Room Air Motion 5-step approach  Primary air  Total air  Convection currents  Room intake  Room air © 2010. All rights reserved
  20. 20. Step 1: Identify the Primary Air Primary Air - mixture  Primary air patterns are of air supplied to the outlet temperature independent1 and induced room air  Catalog Throw: within an envelope of velocities > 150 FPM  150 – 100 – 50  10 - 17 - 25 Inside Step 1 Exposed Wall Primary Air Wall Outlet © 2010. All rights reserved
  21. 21. Step 2: Identify the Total Air  Total Air - mixture of  Temperature difference primary air and room air between total air and room air which is under the influence produces a buoyancy effect of the outlet conditions which cause the cool air to drop and the warm air to rise  Air has a tendency  Total air has no defined to scrub surfaces terminal velocity limit Step 2 Total Air © 2010. All rights reserved
  22. 22. Step 3: Identify Natural  Convection Currents  Natural Convection  Affects room air motion Currents - Caused by and affects the comfort difference in temperature in the space between room air and air in contact with a warm or cold surface Step 3 Natural convection currents and stratification zone © 2010. All rights reserved
  23. 23. Step 4: Identify the Return Intake  Return Intake - return  Even natural convection intake affects only the currents will overcome the air motion within its draw of the intake immediate vicinity © 2010. All rights reserved
  24. 24. Step 5: Identify the Room Air  Room Air Diagram is complete  Most uniform air motion is when remaining room air drifts between stratification zone back towards the primary air and total air and total air  Highest air motion is in and  Lowest air motion is near the primary and total air in stratification zone © 2010. All rights reserved
  25. 25. Mapping Throw © 2010. All rights reserved
  26. 26. Mapping Throw Cooling © 2010. All rights reserved
  27. 27. Estimating Downward Projection  Chart provides vertical throw of a free jet to 50 fpm for heating and cooling with the same diffuser. 23 40 28 1000 fpm  Typically, cfm and jet velocity are known.  2009 Fundamentals Chapter 20 1000 cfm +10 -20 0 © 2010. All rights reserved
  28. 28. ADPI & Comfort Air Diffusion Performance Index Statistically related the space conditions of local or transversed temperature and velocities to occupants’ thermal comfort ADPI >= 80 is considered acceptable Effective draft temperature  = (tx-tc) – 0.07(Vx-30)  % of points where -3<= <= +2 = ADPI  Velocity below 70 fpm © 2010. All rights reserved
  29. 29. ADPI The grey area represents -3<= <= +2 You can vary temperature or velocity to maintain comfort 15 fpm = 1 °F © 2010. All rights reserved
  30. 30. Throw vs. Characteristic Length © 2010. All rights reserved
  31. 31. ADPI Selection Illustration Point A ADPI Min 80 ADPI Min Max 0.6 1.2 20x20 Room 400 cfm = 1 cfm/sq ft Characteristic Length = 10 Therefore, look for T50 = 12 feet at 400 cfm (Max VAV) Check Turndown point at .6 T50/L (Min VAV) Set constant volume systems at Point A. T50/L © 2010. All rights reserved
  32. 32. Recommended ADPI Ranges for Outlets Outlet T50/L Range Calculated T50 & L Data Sidewall Grilles L 10 15 20 25 30 1.3-2.0 T50 13-20 20-30 26-40 33-50 39-60 Ceiling Diffusers L 5 10 15 20 25 Round Pattern 0.6-1.2 T50 3-6 6-12 9-18 12-24 15-30 Ceiling Diffusers L 5 10 15 20 25 Cross Pattern 1.0-2.0 T50 5-10 10-20 15-30 20-40 25-50 Slot Diffusers L 5 10 15 20 25 0.5-3.3 T50 3-18 5-33 9-50 10-66 15-83 Light Troffer L 4 6 8 10 12 Diffusers 1.0-5.0 T50 4-20 6-30 8-40 10-50 12-60 Sill & Floor Grilles L 5 10 15 20 25 All Types 0.7-1.7 T50 4-9 7-17 11-26 14-34 18-13 © 2010. All rights reserved
  33. 33. ASHRAE Standard 62.1 Table 6.2 Ventilation Air Ez Factor Ceiling supply of cool air 1.0 Ceiling supply warm air < 15 °F Δt 1.0 150 fpm supply jet reaches 4.5’ AFF Ceiling supply warm air >15 °F Δt 0.8 Floor supply cooling ceiling return UFAD:  T 50 > 4.5’ AFF 1.0  T 50 < 4.5 AFF (RP-1373) 1.2 Displacement Ventilation 1.2 © 2010. All rights reserved
  34. 34. Typical Perimeter Solution  50/50 throw pattern is the best compromise for both heating and cooling  Half of the air is always directed in the wrong direction  ASHRAE Std. 62.1-2007  T150 to 4’-5’ AFF  Max Δt = 15 °F © 2010. All rights reserved
  35. 35. Auto Changeover Diffuser Solution Diffuser Cooling Window Air flow does not pause in intermittent pattern to cause sustained drafts pop action of air flow pattern. Sill Heating © 2010. All rights reserved
  36. 36. Auto Changeover Diffuser  Vertical Pattern For Heating  Horizontal Pattern For Cooling  30% Increase In Energy Efficiency  Room reaches set-point faster  Room Stratification for heating similar to cooling © 2010. All rights reserved
  37. 37. Sills & Soffits on Perimeter  Soffits cause air to turn Soffit up prematurely  Aim air under the soffit to hit the glass or cold wall  Sills deflect cold air into the room  Sill height sets the stratification layer height Sill © 2010. All rights reserved
  38. 38. Air Distribution, Partition Effects © 2010. All rights reserved
  39. 39. Partially Mixed Air Distribution UFAD – Interior Zone Perimeter with Series Fan Terminal Perimeter with Plenum VAV Cooling Perimeter with Passive Heating © 2010. All rights reserved
  40. 40. Underfloor Air Distribution (UFAD) Stratified Zone © 2010. All rights reserved
  41. 41. Round Access Floor Diffuser High induction air flow pattern Occupant adjustable damper  Actuated version available Typical design point is 80-100 cfm Throw between 4-5 ft. Low NC © 2010. All rights reserved
  42. 42. Interior Applications Use Conventional Components…  Round (Swirl) Diffusers  Rectangular Diffusers In Conventional Applications  One per worker or area measure © 2010. All rights reserved
  43. 43. Series Fan Terminal for Perimeter Used in perimeter and conference rooms  Any room with varying loads 10 ½”, and 14” tall units for 12” and 16” raised floors 300 cfm to 1200 cfm Standard series fan powered terminal Primary supply air damper  Supply pulls from the floor  Option for two dampers © 2010. All rights reserved
  44. 44. Typical Perimeter Installation Low horsepower fan powered terminal unit ducted to rectangular floor diffuser plenums © 2010. All rights reserved
  45. 45. Plenums  Plenum sizes vary  8” x 16”  10” x 10”  12” x 12” Cores are available in multi-piece  2-way or 4 way blow © 2010. All rights reserved
  46. 46. ECM Motor Electronically Commutated Motor © 2010. All rights reserved
  47. 47. ECM Motor Brushless, DC motor Converts AC to DC for motor Ultra high efficiency motor  Efficiencies of up to 70% across the entire operating range Energy savings Control of fan speed through DDC controller © 2010. All rights reserved
  48. 48. Energy Savings 350 watts savings = .350 kW 250 days/year x 12 hours/day = 3000 operating hours/year .350 kW x 3000 hours = 1050 kWh 1050 kWh x $.10 per kWh = $105 per unit per year energy savings!  Does not include demand charges © 2010. All rights reserved
  49. 49. PWM  The ECM motor is controlled by a PWM (Pulse Width Modulated) signal Voltage pulses over a specific time period Voltage is proportional to cfm Low voltage device Manual PWM is adjusted like a SCR, with a screwdriver Remote PWM is controlled by a 0-10V signal from the DDC controller © 2010. All rights reserved
  50. 50. Additional ECM Benefits Soft start  Motors are set to start up slowly No brushes  No noise associated with brushes  Titus has found no significant overall sound reduction with the ECM motor  No wearing of brushes ECM motor life is ~90,000 hours (30 years of typical series fan box life) Cooler operation © 2010. All rights reserved
  51. 51. Linear Perimeter System  (Variable Air Volume)  (Water Heat)  (SCR Electric Heat)  (Return) © 2010. All rights reserved
  52. 52. Perimeter Linear Diffuser Solution © 2010. All rights reserved
  53. 53. Transverse Apertures © 2010. All rights reserved
  54. 54. Transverse Apertures © 2010. All rights reserved
  55. 55. Transverse Apertures © 2010. All rights reserved
  56. 56. Perimeter Smoke Demo Video © 2010. All rights reserved
  57. 57. Interior Zone VAV Cooling Conference Waiting Area © 2010. All rights reserved
  58. 58. Underfloor  System Christman Linear Heat 3900 Btu/h 4’ Length © 2010. All rights reserved
  59. 59. Fin tube application © 2010. All rights reserved
  60. 60. Fully Stratified Air Systems Energy & Comfort Optimization (ECO) Basic system concepts Displacement diffusers © 2010. All rights reserved
  61. 61. DV‐ Basic Concepts Supply Air TL = 65°F  Higher supply air temperature  Air change effectiveness factor of 1.2 Clear Zone © 2010. All rights reserved
  62. 62. Displacement Ventilation Applications Good application  Room height > 9.5 ft  Open Plan Offices, Classrooms, & Meeting Rooms  Casinos, Restaurants, Theaters, & Auditoriums © 2010. All rights reserved
  63. 63. Displacement Ventilation Applications Poor application  Room height < 8 ft  Surplus heat is the main problem – not air quality  In combination with chilled beams © 2010. All rights reserved
  64. 64. System Equipment Higher equipment efficiency  Uses warmer supply air  65°F compared to 55°F  Energy consumption is often reduced by raising discharge temperature © 2010. All rights reserved
  65. 65. System Equipment Lower horsepower fans  0.04 in. pressure is required for proper diffuser performance  Results in lower horsepower fans required © 2010. All rights reserved
  66. 66. HVAC System Benefits 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 © 2010. All rights reserved
  67. 67. Perimeter Heating Perimeter heating cannot be accomplished with the displacement ventilation system Separate system is required: © 2010. All rights reserved
  68. 68. Return Air Located at ceiling Allows heat from ceiling light to be returned before it is able to mix with occupied zone © 2010. All rights reserved
  69. 69. Return Air If 55oF supply air is used for humidity reasons, return air can be mixed with plenum air to achieve 65oF air If 65oF supply air is used, return air can be brought back to the air handling unit to be filtered and dehumidified © 2010. All rights reserved
  70. 70. Temperature Gradient ASHRAE Standard 55:  Occupied Zone  < 5.4°F Risk of draft increases if ∆t > 36°F between supply and exhaust air (Displacement ventilation, REHVA) © 2010. All rights reserved
  71. 71. Temperature Gradient Ceiling Height 9’-14’ 50% Rule is applied 62°F – 72°F – 82°F 10°F - 10°F (Displacement ventilation, REHVA) © 2010. All rights reserved
  72. 72. Temperature Gradient 33% Rule for > 14’ room heights 33% 67% 64°F – 72°F – 86°F 8°F - 14°F (Displacement ventilation, REHVA) © 2010. All rights reserved
  73. 73. Adjacent zone Discharge Velocity < 80 fpm Area where air velocity exceeds 50 fpm Occupants should not be stationed within the adjacent zone © 2010. All rights reserved
  74. 74. Comfort with Adjustable Air Patterns  Standard adjacent zone from factory  Modified adjacent zone after adjusting pattern controllers to change pattern © 2010. All rights reserved
  75. 75. Comfort Air Distribution The ASHRAE 2009 Fundamentals handbook, Chapter 20, 2007 Applications handbook Chapter 56, and 2008 Systems & Equipment handbook provides guidance on diffuser selection. Select throw at Max. & Min. to meet ADPI guidelines. It cost less for install a good design than to replace a bad design. Employees cost 70 times the cost of Energy. © 2010. All rights reserved
  76. 76. Questions?

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