Air Diffusion Designing for Comfort

Transcription

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2 Air Diffusion Designing for Comfort

3 Occupant Comfort Air Diffusion Selection ADPI Air Diffusion Performance index Ventilation Effectiveness Induction Room Space Induction Design Criteria ISO7730 ASHRAE 55p Design & Selection Software Products

4 Occupant Comfort

5 Comfort Limits ASHRAE Standard and ISO ADPI Air Diffusion Performance Index / Comfort Index When is a person comfortable? A person is thermally comfortable when their body heat loss equals their heat production without them sensing any changes in temperature.

6 Body Heat Loss or Gain Heat Loss or Gain can occur through: Conduction transfer of heat across a body Convection transfer from a body to its surroundings Radiation transfer through electromagnetic waves Evaporation sweat

7 Personal Comfort Variables - Clothing - Activity - Metabolic rate

8 Space Comfort Variables - Dry bulb temperature - Relative humidity - Air velocity - Noise

9 ASHRAE Defines Comfort ASHRAE Definition of Comfort Fanger s comfort index or PMV.

10 ASHRAE Definition of Comfort ASHRAE/ISO 7730 standard defines comfort as: - Maintaining a temperature of C - Relative humidity of 25 60% - Maximum velocity within the occupied zone of 0.25 m/s Cooling & 0.15m/s Heating

11 Effect of Air Motion on Comfort The percentage of dissatisfied occupants at the Neck Region.

12 Effect of Air Motion on Comfort The percentage of dissatisfied occupants at the Ankle Region.

13 Design Criteria ISO7730-ASHRAE 55P-APDI Thermal Resistance of Clothing - Clo Value Provided Metabolic there Rate is Occupants sufficient Physical heating Activity & cooling to meet the thermal and humidity control requirements, comfort is almost completely a Air Temperature Optimum Operative Temperature function Air Velocity of the Mean space Space air distribution. Velocity S.A. Mumma, Ph.D P.E., Fellow ASHRAE Relative Humidity Mean Radiant Temperature

14 Air Diffusion Selection

15 Air Distribution Air Diffusion Design & Selection

16 Defining the Occupied Space

17 Terminal Velocity Terminal Velocity Tv m.75 m/s.50 m/s.25 m/s 7.3 m 15.6m

18 Free Expansion A free jet will expand at 22. Zone 1 Zone 2 Zone 3 Zone 4 Laminar, induction increases Laminar, induction increases Exit velocity with initial induction Laminar/Turbulent, maximum Room induction

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20 Hot and Cold Jets If the supply air is warmer than the room temperature, it will rise. However if the supply air is cooler than the room air, it will drop. General Rule: T0.25 is effected at 2% per Degree T

21 Example 5 0 C Delta T Heating 10% T 0.25 Throw@0.25m/s General Rule: 0.25 is effected at 2% per Degree T

22 With overhead heating, the air slows down and turns upwards at roughly 0.50 to 0.75m/s. Considerations 0.5 to 0.75m/s

23 Furniture against wall Considerations

24 Colliding jets Air Diffusion Mistakes

25 ADPI Air Diffusion Performance Index

26 ADPI Effective Draft Temperature Effective Draft Temperature is calculated by: q = ( - )- ( - ) t x t c 8 V x 0.15 where : q = t t x c V x = = = effective draft temperature (K) local jet dry-bulb temperature ( C) control room dry-bulb temperature ( C) local jet centreline velocity (m/s)

27 ADPI & Effective Draft Temperature The ADPI is the percentage of locations where measurements are taken which have an: Acceptable _ Effective Draft Temperature. Total number of q within acceptance Total number of values measured X 100 An acceptable value for Effective Draft Temperature is within and , with a velocity of less than 0.35m/s

28 ASHRAE Definition of Comfort PMV Comfort as a function of air velocity and temperature.

29 ADPI Effective Draft Temperature

30 Air Diffusion Performance Index Effective draft temperature, q ( t -t )-8( V -0.15) = x c x t c 1700mm 1100mm 600mm 100mm q 1 q 100 t x and V x

31 ADPI Air Diffusion Performance Index Effective draft temperature, q ( t -t )-8( V -0.15) = x c x Room Temp = 22 0 C 30 Test points at 0.1m/s, 20 C 35 points at 0.2m/s, 21 C 20 points at 0.3m/s, 22 C 15 points at 0.4m/s, 22 C so if 30 points = points = points = points = -2 ADPI = 85 q = 1 = ( tx - tc )-8( Vx ) ( 20-22) -8( ) = -1.6 q2 = -1.4 q = q4 = ADPI = = 0.85 = 85%

32 Air Diffusion Performance Index Selection Guide

33 Air Diffusion Performance Index Ratio T Throw distance at terminal velocity 0.25m/s L Characteristic room length

34 Terminal Velocity Tv m.75 m/s.50 m/s.25 m/s 7.3 m 15.6

35 Characteristic Room Length L Characteristic room length for various Air Diffusion Products Diffuser Type High Sidewall Register Circular Ceiling Diffuser & Swirl Diffusers Sill Grille Ceiling Slot Diffuser Light Troffer Diffusers Perforated, Louvered Ceiling Diffusers Characteristic Length (L) Distance to wall perpendicular to jet Distance to closest wall or intersecting air jet Length of room in direction of flow Distance to wall or mid plane between outlets Distance to mid plane between outlets plus distance from ceiling to top of occupied zone Distance to wall or mid plane between outlets

36 ADPI Selection Example

37 Example Mapping Throw 6 m 2.7 m A consulting engineer is selecting a diffuser for the room above. The room requires 250 l/s at an NC no greater than 35.

38 Example Mapping Throw 1.5 m 3 m 1.5 m 2.7 m 0.4 m 0.4 m They selected 2 x CFP600/12, with 125l/s for each. Total air quantity 250l/s, with a throw of 0.25m/s. An NC value of 14. Will the occupants be comfortable?

39 Example Using ADPI ADPI 130W/m2 for 80 target - ratio = m 3m 1.5m 2.7m 0.4m 0.4m T ADPI calculation = = = L 1.5

40 Example Mapping Throw If our selection 1 x CFP600/24 Radial Swirl diffuser. Total volume 250l/s - Throw - NC = 26 Will the occupants be comfortable? 3m 3m 2.7 m

41 Example Using ADPI ADPI 130W/m2 for 80 target - ratio = m 3 m 2.7 m T ADPI calculation = = = L 3

42 ADPI Selection T L

43 ADPI Selection T L

44 ADPI Selection

45 ADPI Design Expectations APDI - Ensures proper Selection, Application and Deployment of Air Diffusion Equipment High APDI equates to High Air Change Effectiveness (ACE) Value ADPI Method is suitable for heating at <10 0 C ΔT ADPI method is effective for CAD (as low 5 0 C) Cold Air Distribution Design Manual TR Research Project )

46 Ventilation Effectiveness

47 Ventilation Effectiveness Air Change Effectiveness (ACE) ANSI/ASHRAE Standard ASHRAE Fundamentals F Principally it is an evaluation of effective mixing of the Supply/Outdoor with Room/ Space Air

48 Induction

49 Induction, High Induction & Induction Ratios High Induction means High Exit Velocity High Induction means High Pressure Higher pressure offsets (CAD) Design Savings High Induction = Smaller Air flows or more Diffusers or more Noise

50 Induction, High Induction & Induction Ratio Room Air Induction Equation There is no accepted published method Qx for determining = = the C induction Vo ratio of an Qo Vx individual diffusion product Induction Ratio Q Where: Induction Ratio = Primary Qx: Air / Induced Air Qx = Qo X C Vo Vx Qo: = Supply volume m3/s = Induction volume at Distance Vo: = Discharge Velocity m/s Vx: = Velocity at distance m/s = Entrainment Coefficient 1.4 for infinite slots and 2.0 for round free axial jets Temperature Measurements C: of Primary Air, Discharge Air and Induced Air

51 Holyoake Swirl Diffusers Series CFP CFP - 600/24 Aeff: m2 Veff: 0.7-3m/s Air Flow: L/S Pa: 2-13 NC <10-30 CFP - 600/20 Aeff: m2 Veff: 0.5-3m/s Air Flow: L/S Pa: 6-12 NC CFP - 600/12 Aeff: m2 Veff: 0.5-3m/s Air Flow: L/S Pa: 2-18 NC <10-20 Flexible Volume range suitable for VAV Systems High Mixing Turbulent Radial Swirl Air Pattern Good induction Low Pressure - Low Noise High Range VAV Blade Design and Turbulent Radial Mixing

52 Induction, Room Induction - Room Induction Ratios Q Air Volume 200L/S = 2.16 m/s Exit Velocity Air Volume100L/S = 1.08m/s Exit Velocity Swirl Diffuser Tv@0.25m/s Swirl Diffuser Tv@0.20m/s (Figure 9) 3456 L/S Room Induction Ratio Q = Air Volume 200L/S = 2.16 m/s Exit Velocity CFP/600/20 (Figure 8) 1080 L/S Room Induction Ratio Q = 10.8 Air Volume100L/S = 1.08m/s Exit Velocity Swirl Diffuser Tv@0.15m/s Swirl Diffuser Tv@0.10m/s 5760 L/S 2160 L/S (Figure 11) Room Induction Ratio Q = 28.8 (Figure 10) Room Induction Ratio Q = 21.6

53 Design Criteria ISO7730 ASHRAE 55P PVM Predicted Mean Vote - PPD

54 Design Criteria ISO7730-ASHRAE 55P-APDI Thermal Resistance of Clothing - Clo Value Metabolic Rate Occupants Physical Activity Air Temperature Optimum Operative Temperature Air Velocity Mean Space Velocity Relative Humidity Mean Radiant Temperature

55 Thermal Comfort Considerations & Obligations Design to a Predetermined PMV-PPD As a function of: Clothing, Metabolic Rate. Air temp, Radiant Temp, Velocity, Humidity <6% PD <10% PD <15% PD Establish Optimum Operative Temperature Range <6% PD <10% PD <15% PD Establish the draft rating DR PD (mean velocity) encompassing: Local Air Temperature, Local air velocity, local turbulence intensity <15% PD <20% PD <25% PD 0.62 DR 34 -ta v ( )( ) ( 0.37 v 3.14) = Tu

56 Thermal Comfort Considerations & Obligations Determine Ventilation rate for Perceived Indoor Air Quality as a result of Occupant numbers and Building Materials <15% PD <20% PD <30% PD Establish your Ventilation rate for Air Quality as a result of Occupant numbers and Building Materials <15% PD <20% PD <30% PD Confirm Design Ventilation Effectiveness Green Star requires Veff 0.95

57 Thermal Comfort Considerations & Obligations Establish required Flow Rate for Thermal Design in accordance with optimal operating temperature Ensure Acoustics meet Environment standards Category (A) Category (B) Category (C) Establish and Confirm ADPI Rating >80 Effective Draft Temperature : local temperature, room average temperature, local velocity ( tx -tc)-8( -0.15) q = Vx

58 Calculation for PMV for resultant PPD

59 Design & Selection Software

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61 Air Distribution Design Program ADE:5.4

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71 Products

72 Architectural Louvers

73 CSDF Fixed Pattern Linear Slot

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75 CSD-P Flangeless Linear

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77 LF1200 Flangeless Extruded Linear Bar Diffuser

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79 Thankyou for Listening

80 Predicted Mean Vote Percentage Dissatisfied P. Ole Fanger Director, Professor, D.Sc. International Centre for Indoor Environment and Energy Technical University of Denmark, Building 402 DK-2800 Lyngby, Denmark.