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Third Year > Air Flow > Flashcards

Air Flow Flashcards

1
Q

What are 3 advantages of having blowers set for continuous operation?

A

Improve air filtration
Increase building comfort
Reduce temperature variations

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2
Q

A duct system that is designed for a heating only system will be sufficient size if you want to add cooling to it ?

A

False, you would need to increase the size.

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3
Q

Why is it important to balance a residential hvac system?

A

If not done properly the end result will be cold areas in the building

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4
Q

Dwyer air meters can measure cfm directly?

A

False
Feet per minute velocity
Cfm is a volume

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5
Q

Manometers are filled with alcohol ?

A

False
Made with oils or water

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6
Q

Which of these two instruments are the most accurate?

Inclined manometers
U-tube manometers

A

Inclined

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7
Q

A velometer cannot be used to measure static pressures over ?

A

10” of water column

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8
Q

What are the two basic types of anemometers?

A

Thermal
Rotating vane

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9
Q

What is atmospheric pressure at sea level ?

A

14.7 Psia

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10
Q

What is static pressure ?

A

Air will exert pressure on the walls of the vessel in which it is confined

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11
Q

What is static pressure ?

A

Air will exert pressure on the walls of the vessel in which it is confined

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12
Q

What is total pressure ?

A

The sum of the static and velocity pressures

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13
Q

What causes dynamic pressure losses?

A

They are when there are changes in direction and velocity of air flow

When an airstream makes turns diverges converges narrows widens enters exits or passes dampers gates coils filters or sound attenuators

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14
Q

What is aspect ratio?

A

Ratio between width and height of the duct

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15
Q

Define equivalent length

A

Comparison of calculated pressure drop through a fitting to the pressure drop through a straight length of duct of the same size

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16
Q

What is the maximum recommended aspect ratio for rectangular duct ?

A

Avoid using duct with an aspect ratio greater than 4:1 if possible in addition to increasing friction loss it costs more to fabricate

17
Q

How is the radius ratio of an elbow calculated?

A

By using centerline radius (one half the width of the elbow plus the throat radius ) of the elbow and dividing it by width of the elbow

18
Q

What is the purpose of splitters in an elbow ?

A

Splitters are installed in elbows to reduce the dynamic pressure losses

19
Q

What is the maximum angle of eccentric diverging fitting ?

A

30degrees

20
Q

What is the maximum angle of a concentric diverging fitting ?

A

60 degrees

21
Q

Where would a two piece streamliner be used ?

A

Used in areas where the ductwork cannot be made to offset around an obstruction that would exceed 20% of the cross sectional area of the duct .

22
Q

Turning vanes are designed for what ?

A

Reduce turbulence

23
Q

What air pressures are measured using the inner tube of a pitot tube ?

A

Total

24
Q

What instrument measures only atmospheric pressure

A

Barrometer

25
Q

What is dynamic pressure loss

A

A loss caused by a change of direction

26
Q

What happens when Increase in static pressure after diverging fitting

A

Static regain

27
Q

How do u directly measure air volume

A

Barometer

28
Q

Squat throat square heel turning vein included angle ?

A

If it’s a 90degree elbow then 90 degrees

29
Q

A properly designed hvac system will have a good balance of what two things ?

A

Supply air return air

30
Q

What is the result of running a blower on continuous low speed ?

A

Continuous conditiong of the air

31
Q

Operating a blower continuously will prevent ?

A

Stratification

32
Q

What air pressures are measured using inter tube of a pilot tube ?

A

Total

33
Q

What instrument measures only atmospheric pressure ?

A

Barrometer

34
Q

What is dynamic pressure loss

A

A loss caused by change in direction

35
Q

What is it called when Increase in static pressure after diverging fitting

A

Static regain

36
Q

A properly designed hvac system will have a good balance of what two things ?

A

Supply and return air

37
Q

Operates a blower continually will prevent ?

A

Stratification

Third Year (7 decks)

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