Industrial Ventilation vs. IAQ

Industrial Ventilation vs. IAQ

Heating

Ventilation

Air

Conditioning


HVAC System Functions

Heating

Cooling

Ventilation

Filtration

Dehumidification

Humidification

Distribution

Routes of Entry

• Inhalation

• Ingestion

• Absorption

• Injection

Control Options

• Process change

• Substitution

• Isolation

• Ventilation

• Administrative control

• Personal protective equipment

Problem Characterization

BURTON 2-1

EMISSION SOURCE

AIRFLOW

Burton Ex. 2-1

BURTON 2-4

GROUP EXERCISE

Study the figure on page 2-4 and discuss potential control measures that you might use to correct the problem.

THE BEHAVIOR OF AIR

The Atmosphere

• Reaches 50 miles into space.

• Pressure = 14.7 pounds per square inch.

Composition of Air

Percentage Composition by Volume

Nitrogen

Oxygen

Argon

Pressure Measurement

VacuumAtmospheric Pressure14.7 psia

Pressure Measurement

14.7 psia =407in. Water

14.7 psia =29.92 in. Mercury (Hg.)

How Do We Make Air Move ?

Pressure

• Differences in air pressure cause movement.

Pressure Differential Causes Movement

BURTON 3-6

FLOW LOW HIGH

FAN

Negative Pressure = Less Than Atmospheric

Positive Pressure = Greater Than Atmospheric

Pressure Relationships

Pressure Terms

• Static Pressure

• Velocity Pressure

• Total Pressure

Static Pressure

SPFlow

Static pressure (SP) isexerted in all directions.

Velocity Pressure

SPFlow

Velocity Pressure (VP) iskinetic (moving pressure) resulting from air flow.

VP

Total Pressure

SPFlow

Total pressure (TP) is the algebraic sum of the VP and SP.

VP

TP

Pressure Upstream and Downstream of the Fan

BURTON 3-8

TP SP VP

Up-stream - - +

Down-stream + + +

What is use of the term “Velocity Pressure” ?

• Determine the air flow.

• To design the system.

• V = 4005(VP)1/2

What is use of the term “Static Pressure” ?

• Accelerate the air.

• Overcome resistance to friction.

Static Pressure and Velocity Pressure are Mutually

ConvertibleWhen air is accelerated, the static pressure is converted to velocity pressure.

When air is decelerated, the velocity pressure can be transformed back into static pressure.

=

Conservation of Mass

• Mass in = Mass out.

• Air speeds up when the duct area is smaller.

Q = VA

Q = Cubic Feet Per MinuteV = VelocityA = Area

Dilution Ventilation

BURTON 4-1

YES• non-hazardous

• gas, vapor, respirable particle

• uniform time emission

• emissions not close to people

• moderate climate

NO• toxic material

• large particulate

• emission varies widely over time

• large, point source emissions

• people in vicinity

• severe climate

• irritation or complaints

Volume Vapor Flow Rate

BURTON 4-3

Estimating Dilution Air Volume

BURTON 4-5

Poor Dilution

Good Dilution

Example 4-1

BURTON 4-6

What is q, the volume flow rate of vapor formed, if 0.5 gallons of toluene are evaporated uniformly over an 8-hr. shift? What volume flow rate Qd is required for dilution to 10 ppm, if Kmixing = 2 ? (Assume STP; d = 1.0)

What is the average face velocity of air in a room 10ft. * 8ft. * 40ft for these conditions?

Strategy Ex. 4-2

Step 1: Calculate the volume flow rate of the vapor

emitted q.

q = (387 * lbs. evaporated)/ (MW * t * d)

Note:lbs. Evaporated = gal. * 8.31 * SG

Step 2. Calculate the dilution air volume flow rate

Qd.

Qd = q * 106 * K mixing

Ca (ppm)

Step 3: Calculate the face velocity.

V face = Qd/A

Step 4: Calculate the air changes/ hour.

N = (Qd * 60)/Vr

Purge and Buildup

BURTON 4-9

• Purge and buildup - predict contaminant buildup or purge rate.

• Steady state -equilibrium maintained.

Example 4-5

An automobile garage was severely contaminated with carbon monoxide.

How long will it take to purge the garage?

BURTON 4-11

BURTON 11-1

Chapter 11 - Makeup Air Balance

• Exhausted air must be replaced.

• Negative pressure without makeup air.

Make up Air

• Fresh air supplied into the breathing zone of the associate.

Overcoming Negative Static Pressure

BURTON 11-2

• Changes in static pressure involving radial (squirrel cage) fans cause a small change in the volumetric flow rate.

• Changes in static pressure involving axial (propeller) fans cause a large change in the volumetric flow rate.

Good Makeup Air

INDUSTRIAL VENTILATION 2-4

Bad Makeup Air

INDUSTRIAL VENTILATION 2-4

Reentrainment

BURTON 11-9

Avoiding Reentrainment10-50-3000 RULE

BURTON 14-5

Recirculation of Exhaust Air

BURTON 12-1

• Good for non-toxic particulate control.

• Can recover 40-60% of heat energy.

Types of Ventilation Systems

BURTON 5-1

Why Choose Local Ventilation?

BURTON 5-2

• No other controls • Containment• Employee in vicinity• Emissions vary with

time• Sources large and

few• Fixed source• Codes

Exercise 5-3

BURTON 5-3

Form your group and try exercise 5-3. Compare the operation to the parameters listed below:

• No other controls available

• Hazardous contaminant

• Employee in immediate vicinity

• Emissions vary with time

• Emission sources large and few

• Fixed emission source

• Codes & standards

Components of a Local Exhaust System

BURTON 5-4

Static Pressure Review

BURTON 5-5

Energy Conservation

BURTON 5-6

Basic Air Flow Equations

BURTON 5-7

• Q = V * A

• TP = SP + VP

• V = 4005(VP/d)0.5

Static Pressure Loss

BURTON 5-8

• Static Pressure Loss = Kloss * VP * d

Elbow Loss

BURTON 5-9

Air moving through elbows spends static pressure because of:

• directional change • friction • shock losses• turbulent mixing• air bunching up • SP(loss) = K(elbow )* VP * d

Elbow Loss Ex. 5-8

BURTON 5-9

What is the elbow loss factor K(elbow) where the elbow radius of curvature is R/D = 2.0 in a smooth transition elbow.

Elbow Loss Exercise 5-9

BURTON 5-10

What is the actual loss in inches of water of air flowing through a 60-degree, 3-piece elbow at V = 3440 fpm? R/D = 1.5, STP, d=1.

Elbow Loss Exercise 5-9

• SPloss = K * VP * d

• Use Chart 13, Appendix pg. 25 for information on a 90-degree 3- piece elbow with R/D = 1.5

• Let K = (angle/90) * K 90

• VP = (V/4005)2

Friction Loss as a Function of Duct Length

BURTON 5-11

Friction Loss = K * VP * L * R * d• K is a value taken from Chart #5,

appendix page 9 • VP is duct velocity pressure, in w.g.• L is the length of the duct in feet• d is the density correction factor• R is roughness correction factor

Exercise 5-10

What is the friction loss for a length of galvanized duct with the following parameters? D = 8in., Q = 1000scfm, L = 43 ft. R = 1.

Tee Losses

BURTON 5-11

Tee Losses Ex. 5-12

BURTON 5-12

What is the estimated static pressure loss in inches of water for a branch entry of 30 degrees where the branch entry velocity is 4500 fpm?

Converting Static Pressure To Velocity Pressure

BURTON 6-2

At the hood, all of the available static pressure is converted to velocity pressure and hood entry loss.

SPh = VP + he

Measuring Hood Static Pressure

BURTON 6-2

Measure hood static pressure 4-6 duct diameters downstream from the hood.

4-6 D

Hood Entry Losses

BURTON 6-2

The hood entry loss is the sum total of all losses from the hood face to the point of measurement in the duct.

SP(loss) = K * VP * d

he = K * VP * d

BURTON 6-3

Example 6-1

What is the hood static pressure when the duct velocity pressure is VP = 1.10 in. w.g. and the hood entry loss is

he = 1.00 in w.g.

SPh = VP + he

SPh = 1.10+ 1.00

= -2.10 in w.g.

Vena Contracta

BURTON 6-3

The greatest loss normally occurs at the entrance to the duct, due to the vena contracta formed in the throat of the duct.

Hood Efficiency

BURTON 6-4

A hood’s efficiency can be described by the ratio of actual to ideal flow. This ratio is called the Coefficient of Entry, Ce.

Ce = Q(actual)/Q(ideal)

Hood Static Pressure and Entry Losses Example 6-5

BURTON 6-5

The average velocity in a duct serving a hood is V = 2000 fpm. The loss factor for the hood has been obtained from the manufacturer as Khood = 2.2. What are the he and SPh? (Assume STP, d = 1)

Hand Grinding Table Example 6-6

BURTON 6-6

Assume that a special hand grinding table hood has been built and the following data have been measured:

SPh = -2.50 in w.g., V = 4000fpm, and the duct diameter is 18 in. (Assume STP, d=1)

Types of Hoods

• Receiving

• Capturing

• Enclosing

BURTON 6-10

Hood Types

• SLOTTED HOOD

Hood Types

• ENCLOSED HOOD

Hood Types

• ENCLOSING HOOD

Hood Types

• CAPTURING HOOD

Grinding Wheel Hood Example Example 6-9

BURTON 6-12

Determine the volume flow rate, transport velocity, duct diameter, loss factor K, Ce, he, and SPh, for a grinding wheel hood, wheel diameter = 13in. (low surface speed), straight take off [sto], STP)

EXERCISE 6-10USEFUL FORMULAS

Q = V * A

V = 4005(VP)1/2

VP = (V/4005)2

he = K * VP

SPh = VP + he

BURTON 6-12 AND 6-13

Exercise 6-10a Where appropriate, determine the volume flow rate,

transport velocity, duct diameter, loss factor K, Ce, he, and SPh for a grinding wheel hood with a wheel diameter of 14 in. (low surface speed, tapered takeoff [tto]. Note: the picture in the book is for a buffing hood.

BURTON 6-12

Exercise 6-10a Strategy

1. Use Chart 11C, appendix pg. 18 to find Q, Vtrans., K, and Ce.

2. Use Chart 5A in appendix pg. 9 to find the diameter of the pipe needed and it’s area.

3. Calculate Vactual = Q/A

4. VP = (Vactual/4005)2

5. he = K * VP

6. SPh = VP + he

Exercise 6-10b

Where appropriate, determine the volume flow rate, transport velocity, duct diameter, loss factor K, Ce, he, and SPh for a hand grinding table 10 feet long by 2 feet wide.

BURTON 6-13

Exercise 6-10b Strategy1. Use Chart 11C, appendix

pg. 18 to find Q, Vtrans., K, and Ce.



4. VP = (Vactual/4005)2

5. he = K * VP

6. SPh = VP + he

Exercise 6-10c

Where appropriate, determine the volume flow rate, transport velocity, duct diameter, loss factor K, Ce, he, and SPh for a band saw used to cut wood that has a blade width of 1 inch.

BURTON 6-13

Exercise 6-10c Strategy

1. Use Chart 11E, appendix pg. 20 to find Q, Vtrans., K, and Ce.



4. VP = (Vactual/4005)2

5. he = K * VP

6. SPh = VP + he

Exercise 6-10d

Where appropriate, determine the volume flow rate, transport velocity, duct diameter, loss factor K, Ce, he, and SPh for a bell-mouthed hood used for welding. X=10 in., Vc = 100 fpm, Vtrans = 3000 fpm.

BURTON 6-13

Exercise 6-10d Strategy

1. Use Chart 11A, appendix pg. 16 to find Q, K, and Ce.



4. VP = (Vactual/4005)2

5. he = K * VP

6. SPh = VP + he

Exercise 6-10e Where appropriate,

determine the volume flow rate, transport velocity, duct diameter, loss factor K, Ce, he, and SPh for a canopy hood used for a hot-liquid open surfaced tank. P = 16 ft., X = 3 ft., Vcontrol = 125 fpm, Vtrans = 2000fpm.

BURTON 6-13

Exercise 6-10e Strategy

1. Use Chart 11B, appendix pg. 17 to find Q, K, and Ce.



4. VP = (Vactual/4005)2

5. he = K * VP

6. SPh = VP + he

Factors Influencing Hood Performance

• Competition• Mixing• Work practices

BURTON 6-17

Canopy Hoods

BURTON 6-19

• Use only for hot processes with rising air.

• Estimate initial and terminal velocities of rising air stream.

• The volume of air exhausted from the hood must exceed the volume of air arriving at the hood face.

• Warm rising air expands as it rises. Make the cross-sectional area of the hood face 125% larger than the plume of hot air.

• Avoid canopy hoods if an employee must work over the source.

Chapter 7Selection and Design of

Ductwork

BURTON 7-1

Exercise 7-2

BURTON 7-4

Standard air (d=1) moves through an 8 in. galvanized duct system at 4000 fpm. Estimate VP, find the loss factors K from the Charts, and then estimate static pressure loss for each component in each branch. (Note: treat the branch entry as two 45-degree entries and use the ACGIH value for K on Chart 14.)

Exercise 7-2a, Flanged Hood

BURTON 7-4

Exercise 7-2b, Plain Duct Hood

BURTON 7-4

Exercise 7-2c, Elbow, 3-piece

BURTON 7-4

Exercise 7-2d, Elbow, 5-piece

BURTON 7-4

Exercise7-2e, Elbow, 4-piece

BURTON 7-4

Exercise 7-2f, Branch Entry

BURTON 7-4

Exercise 7-2g, 50 ft. of Duct

BURTON 7-4

BURTON 7-5

RoughnessExample 7-1

Standard air is flowing in 40 feet of a 24 in. concrete pipe at the 4000 fpm. What is the correction factor, R? The loss factor K?

Duct Shapes

BURTON 7-6

Use round duct whenever possible, it resists collapsing, provides better aerosol transport conditions, and may be less expensive.

Pressure Diagrams

BURTON 7-11

Chapter 8 Fan Selection and Operation

AXIAL FANS• propeller fans

CENTRIFUGAL FANS• radial fans

• forward inclined

• backward inclined

BURTON 8-2

Fan Total Pressure

BURTON 8-3

The fan total pressure (FTP) represents all energy requirements for moving air through the ventilation system.

The fan total pressure is often referred to as the fan total static pressure drop.

FTP = TP outlet - TP inlet

FTP = SPout - VP out - SPin - VP in

FTP = SPout - SPin

Exercise 8-1

BURTON 8-3

Find the Fan Total Pressure given that the SPin = -5.0 in w.g, SPout = +0.40 in w.g.

VPin = VPout = 1.0 in. w.g.

FTP = SPout - SPin =

0.40 - (-5.0) = 5.4 in w.g.

Exercise 8-2Fan Static Pressure

BURTON 8-4

The fan static pressure out of the fan is defined as the fan total pressure minus the average velocity pressure out of the fan.

FSP = Fan TP - VPout

SOP and Fan Curves

BURTON 8-5

To develop a system curve, the fan should be turned at different rpms and the flow and the absolute values of the static pressures at the fan are plotted.

Developing Fan Curves

BURTON 8-6

SOP on Steep Part of Curve

BURTON 8-7

Example 8-1

BURTON 8-8

Choose an appropriate fan for a system operating point of Q = 10,000 scfm and FTP = 1.5 in. w.g.

Exercise 8-3

BURTON 8-8

Find a fan and appropriate rpm for a fan exhausting 15,000 cfm at a fan TP = 2.0 in. w.g.

Exercise8-4

BURTON 8-8

Find a suitable fan and the appropriate rpm for a ventilation system exhausting 480 cfm at a fan TP = 13.8 in. w.g.

Commercial Fan Curves

BURTON 8-9


BURTON 8-10


BURTON 8-11

System Effect Losses

BURTON 8-12

Six-and-Three Rule

BURTON 8-13

Air Horsepower

BURTON 8-14

Air horsepower refers to the minimum amount of power to move a volume of air against the fan total pressure. It represents the power to get the air through the duct system.

ahp = ( FTP * Q * d)/6356

Brake Horsepower

BURTON 8-15

Brake horsepower refers to the actual power required to operate the fan so that it fulfills the job of moving the specified cfm against the FTP. It takes into account fan inefficiencies, i.e. losses in the fan.

bhp = ahp/ME

Shaft Horsepower

BURTON 8-15

Shaft horsepower is bhp plus any power required for drive losses, bearing losses, and pulley losses between the fan and the shaft of the motor.

shp = bhp * Kdl

Rated Horsepower

• Rated horsepower is the nameplate horsepower on the motor.

BURTON 8-15

Example 8-4

BURTON 8-16

What is the required power for the system and what rated power motor would you use?

FTP = 5.0 in. w.g. ,

Q = 12000 scfm

ME = 0.60, Kdl = 1.10, d = 1,

f = 6356

Exercise 8-7

BURTON 8-17

Estimate the ahp, bhp, shp, and the rated power motor you would choose for the following system.

Fan TP = 10.0 in. w.g.,

Q = 5000 scfm

Kdl = 1.15, STP(d=1),

f = 6356, ME = 0.65

Fan Laws

BURTON 8-19

Local Exhaust Ventilation Design

BURTON 9-1

Plenum Design

BURTON 9-3

BALANCING

BURTON 9-4

Balancing during the design phase means adjusting losses in duct runs leading to a junction that the predicted loss in each run is essentially equal.

Example 9-2

BURTON 9-5

Design an local exhaust system based on the criteria listed in the example.

Name: Project: Example 9-2 8 in. duct 7 in. duct

Row Item Source Units (US)

PLANS 1. Duct ID Plans FROM -TO A-B A-B

2. Design Q Chart 11 cfm 1000 1000

3. Transport vel. Chart 9, 11 cfm 3000 3000

4. Slotted hood? Y-R5, N-R12 NO NO

5. Slot velocity Chart 11 fpm

6. Slot area R2/R5 sq. ft.

SLOTS/ 7. Slot VP Chart 7 in. w .g.

PLENUM 8. Slot entry loss factor -1.78

9. Acceleration factor -1

10. Plenum loss factor -2.78

11. Plenum SP R7*R10

12. Duct diameter Chart 5 inches 8 7

13. Duct area Chart 5 sq. ft. 0.0391 0.2673

DUCT 14. Duct velocity R2/R13 fpm 2865 3740

15. Duct VP Chart 7 inches 0.51 0.87

16. Duct length from plans feet 25 25

17. Friction R, duct Chart 10 or from mfg 2.4 2.4

18. Friction K Chart 5 0.03 0.035

19. Friction K, duct R16*R17*R18 1.8 2.1

20. Hood entry Chart 11 0.25 0.25

LOSS 21. Acceleration 1.0 at hoods 1 1

FACTOR 22. Elbow s Chart 13 0.27 0.27

K 23. Branch entry Chart 14 ACGIH 0 0

24. System effect Chart 16 0 0

25. Other K loss 0 0

26. Total K sum R19-R25 3.32 3.62

27. Duct SP R26*R15 inch 1.69 3.15

STATIC 28. SP at FROM location R33 inch 0 0

PRESSURE 29. Jxn. VP change at FROM Chart 14 inch 0 0

30. Other SP loss inch 0 0

31. Total SP at TO R11+(R27toR30) inch 1.69 3.15

32. Is this Governing SP y/n

JUNCTION 33. Governing SP at TO location inch

34. Actual Q = [R2*(R33/R31)^0.5

35. SPh [R11+(R15*(R20+R21))]inch 0.64 1.09HOOD 36. Total slot length plans feet

37. Slot w idth 12(R6/R36) inch

Example 9-3

BURTON 9-11

Design a local exhaust system based upon the criteria listed on this page.

Name: Group Exercise Project: Example 9-3

Row Item Source Units (US)

PLANS 1. Duct ID Plans FROM -TO A-B B-C C-D D-E

2. Design Q Chart 11 cfm 2400 1000 3421 3421

3. Transport vel. Chart 9, 11 cfm 3000 3000 3000 3000

4. Slotted hood? Y-R5, N-R12 YES NO NO NO

5. Slot velocity Chart 11 fpm 2000

6. Slot area R2/R5 sq. ft. 1.2

SLOTS/ 7. Slot VP Chart 7 in. w .g. 0.25

PLENUM 8. Slot entry loss factor 1.78

9. Acceleration factor 1

10. Plenum loss factor 2.78

11. Plenum SP R7*R10 0.7

12. Duct diameter Chart 5 inches 12 8 14 14

13. Duct area Chart 5 sq. ft. 0.7854 0.3491 1.069 1.069

DUCT 14. Duct velocity R2/R13 fpm 3056 2865 3200 3200

15. Duct VP Chart 7 inches 0.58 0.51 0.64 0.64

16. Duct length from plans feet 25 25 40 20

17. Friction R, duct Chart 10 1 2.4 1 1

18. Friction K Chart 5 0.018 0.03 0.015 0.015

19. Friction K, duct R16*R17*R18 0.45 1.8 0.6 0.3

20. Hood entry Chart 11 0.25 0.5 0 0

LOSS 21. Acceleration 1.0 at hoods 1 1 0 0

FACTOR 22. Elbow s Chart 13 0.39 0 1.95 0

K 23. Branch entry Chart 14 ACGIH 0 0.28 0 0

24. System effect Chart 16 0 0 0 0

25. Other K loss 0 0 0 0

26. Total K sum R19-R25 2.09 3.58 2.55 0.3

27. Duct SP R26*R15 inch 1.21 1.83 1.63 0.19

STATIC 28. SP at FROM location R33 inch 0 0 1.91

PRESSURE 29. Jxn. VP change at FROMChart 14 inch 0 0 0.1

30. Other SP loss inch 0 0 4

31. Total SP at TO R11+(R27toR30) inch 1.93 1.83 7.64

32. Is this Governing SP y/n YES NO

JUNCTION 33. Governing SP at TO location inch 1.91

34. Actual Q = [R2*(R33/R31)^0.5 1021

35. SPh [R11+ (R15*(R20+R21))]inch 1.43 0.77HOOD 36. Total slot length plans feet 10

37. Slot w idth 12(R6/R36) inch 1.44

Industrial Ventilation vs. IAQ

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