fans Flashcards

1
Q

3 types of pressure from fans

A

static
velocity
total pressure

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2
Q

airflow through the system is controlled by this

A

damper

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3
Q

type of pressure that air exerts on the inside of duct walls

A

static

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4
Q

type of pressure measured at fan discharge with ducting 90 degrees

A

static

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5
Q

type of pressure caused by air flowing through a duct and is felt only by the surfaces that the air actually strikes

A

velocity

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6
Q

type of pressure measured by connecting one end of the manometer at right angles to the duct wall and the other end with the opening facing the airflow

A

velocity

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7
Q

pressure conversion static to velocity

A

decreasing cross sectional area

converging

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8
Q

pressure conversion velocity to static

A

increasing cross sectional area

diverging

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9
Q

mechanical draft type where pressure in the furnace is below atmospheric pressure.
Fan located between the boiler and the chimney

A

induced draft

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10
Q

centrifugal blade fan most effecient and require less horsepower

A

backward incline blade fan

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11
Q

centrifugal blade fan has a lower speed for the same volume, low speed good for hvac application

A

forward blade fan

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12
Q

centrifugal blade fan are used where high speed requires a stronger wheel

A

radial blade fan

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13
Q

centrifugal fan casing cause this pressure change

A

velocity of static

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14
Q

advantage of axial flow fans

A

low cost

compactness

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15
Q

axial fans should not be used in these system

A

ducted air distribution system

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16
Q

centrifugal or axial fans rotate at higher rpm for same air flow

A

axial

17
Q

tube axial or vane axial has less airflow swirl

A

vane axial

18
Q

another name for impellers on centrifugal fans

A

wheels

19
Q

used on fans with constant speed motors and are the least expensive efficient control

A

outlet damper control

20
Q

radial vanes installed on fan inlet. vane shaft interconnect so that all the vanes rotate open and closed in unison

A

variable inlet vane control

21
Q

used on many centrifugal fans to muffle the loud inlet sound generated by the increased air velocity and air shock as it flows into the eye of the fan wheel

A

air inlet silencer

22
Q

isolator absorb vibration and allow for large thermal movement

A

spring type

23
Q

isolator more compact, less flexible and become hardened with age

A

rubber disk

24
Q

isolator have large capacity to absorb vibration

A

oil type vibration

25
Q

ground brush arrangement mounted on isolated fans to ground the static electricity generated while the fan is running

A

static arrest

26
Q

cooling tower fan blade tip to housing ring clearance

A

1/2% of fan diameter