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Fans Flashcards

1
Q

What is a pitot tube used for?

A

Measuring velocity

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2
Q

In ducting air flow what is Converging and Diverging?

A

Converging is when the area of the duct is decreased converting static pressure to velocity

Diverging the exact opposite

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3
Q

Conversion of static pressure to velocity pressure is done by

A

Decreasing Converging the area

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4
Q

Converting velocity pressure to static pressure is done by

A

Increasing the cross sectional area of a duct. - Diverging.

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5
Q

Arcing of static electricity Ina bearing causes what!?

A

Causes a rough bearing. Leading to bearing failure

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6
Q

When airflow deceases so does system pressure (back pressure) this cyclic behaviour is known as

A

Hunting or Surge

(Sounds like fan is breathing) most pronounced in Axial fans

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7
Q

Name the three general types of axial flow fans

A

Tube axial
Vane axial
Propeller

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8
Q

Centrifugal fans consist of what components

A

Rotating element
Scroll (casing)
Pedestal

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9
Q

Large single auction fans generally use what type of bearing?

A

Double row spherical roller bearing.

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10
Q

High velocity pressure energy of air is converted to static pressure with in

A

The scroll

Scroll is a Volute shaped collection chamber

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11
Q

Three types of mechanical draft

A

Induced
Forced draft
Balanced draft

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12
Q

What is the difference between forced air and induced.

A

Forced is pushing air,

Induced is a a negative pressure below atmospheric pressure

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13
Q

Advantages of mechanical draft

A

Increased efficiency of combustion
Independent of chimney temperate
Independent of atmospheric temperature
Can be regulated

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14
Q

What fan blades are most efficient

A

Airfoil style - capable of exceeding efficiency of up to 85%

Uses less HP

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15
Q

What blades have the highest velocity

A

Forward curved

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16
Q

What are the two types of cooling towers?

A

Atmospheric (using natural draft)

Mechanical

  • forced draft
  • induced draft
17
Q

Fan shafts are supported by bearings in two locations, the fan wheel can be mounted how?

A

The fan wheel can be mounted In between bearings or mounted in an overhung co figuration

18
Q

Fan inlet end may have louvers for volume control, the method of controlling the output of radial flow fans is called…

A

Suction throttling

Note: Outlet damper control is least efficient

19
Q

What type of fan pulls hot hot combustion gasses out of a boiler.

A

Induced fans

Require more maintenance than forced draft fans because of abrasives and fly ash

20
Q

What is the purpose of the scroll fan designe

A

Same as the Volute, creates velocity pressure and changes it into static pressure

21
Q

What blade fans are used where high speed requires a strong wheel construction and high pressure services

A

Radial blade fans

22
Q

What radial blade is ideal for hand eking material

A

Open wheel radial blade

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