Air Flow

Question 1

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

Answer 1

Improve air filtration
Increase building comfort
Reduce temperature variations

Question 2

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

Answer 2

False, you would need to increase the size.

Question 3

Why is it important to balance a residential hvac system?

Answer 3

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

Question 4

Dwyer air meters can measure cfm directly?

Answer 4

False
Feet per minute velocity
Cfm is a volume

Question 5

Manometers are filled with alcohol ?

Answer 5

False
Made with oils or water

Question 6

Which of these two instruments are the most accurate?

Inclined manometers
U-tube manometers

Answer 6

Inclined

Question 7

A velometer cannot be used to measure static pressures over ?

Answer 7

10” of water column

Question 8

What are the two basic types of anemometers?

Answer 8

Thermal
Rotating vane

Question 9

What is atmospheric pressure at sea level ?

Answer 9

14.7 Psia

Question 10

What is static pressure ?

Answer 10

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

Question 11

What is static pressure ?

Answer 11

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

Question 12

What is total pressure ?

Answer 12

The sum of the static and velocity pressures

Question 13

What causes dynamic pressure losses?

Answer 13

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

Question 14

What is aspect ratio?

Answer 14

Ratio between width and height of the duct

Question 15

Define equivalent length

Answer 15

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

Question 16

What is the maximum recommended aspect ratio for rectangular duct ?

Answer 16

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

Question 17

How is the radius ratio of an elbow calculated?

Answer 17

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

Question 18

What is the purpose of splitters in an elbow ?

Answer 18

Splitters are installed in elbows to reduce the dynamic pressure losses

Question 19

What is the maximum angle of eccentric diverging fitting ?

Answer 19

30degrees

Question 20

What is the maximum angle of a concentric diverging fitting ?

Answer 20

60 degrees

Question 21

Where would a two piece streamliner be used ?

Answer 21

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 .

Question 22

Turning vanes are designed for what ?

Answer 22

Reduce turbulence

Question 23

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

Answer 23

Total

Question 24

What instrument measures only atmospheric pressure

Answer 24

Barrometer

Question 25

What is dynamic pressure loss

Answer 25

A loss caused by a change of direction

Question 26

What happens when Increase in static pressure after diverging fitting

Answer 26

Static regain

Question 27

How do u directly measure air volume

Answer 27

Barometer

Question 28

Squat throat square heel turning vein included angle ?

Answer 28

If it’s a 90degree elbow then 90 degrees

Question 29

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

Answer 29

Supply air return air

Question 30

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

Answer 30

Continuous conditiong of the air

Question 31

Operating a blower continuously will prevent ?

Answer 31

Stratification
(Cold air sinks hot air rises )

Question 32

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

Answer 32

Total

Question 33

What instrument measures only atmospheric pressure ?

Answer 33

Barrometer

Question 34

What is dynamic pressure loss

Answer 34

A loss caused by change in direction

Question 35

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

Answer 35

Static regain

Question 36

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

Answer 36

Supply and return air

Question 37

Operates a blower continually will prevent ?

Answer 37

Stratification