Mechanical Air Movement And Control

Question 1

What are two groups or classes of fans ?

Answer 1

Axial (propeller)
Centrifugal (radial)

Question 2

What are three types of axial flow fans ?

Answer 2

Propeller
Tubeaxial
Vaneaxial

Question 3

Can propeller fans handle larger volumes of air ?

Answer 3

Yes at low static pressure

Question 4

Can you connect ductwork to a tube axial disc fan ? If yes explain

Answer 4

Yes but the air is discharged in a spiral motion producing high losses in the duct system

Question 5

What is cubic feet per minute ?

Answer 5

Measure of volume of air moved by fan per minute

Question 6

What are the two general groups of fans

Answer 6

Axial (propeller)
Centrifugal (radial)

Question 7

What are four types of fan blades

Answer 7

Forward curved
Backward inclined
Airfoil
Radial

Question 8

What type of fan has low noise emmison and are suitable for resturants exhaust or wgere air contains moisture or dust ?

Answer 8

Backward inclined

Question 9

How is the location of the motor of discharged determined ?

Answer 9

By facing the drive side

Question 10

What is the difference between a tube axial fan and a vane axial fan ?

Answer 10

Vaneaxial has a guide vanes behind the wheel to improve efficiency by straightening the flow of air

Question 11

What is another name for a centrifugal fan ?

Answer 11

Squirrel cage

Question 12

What are the uses and applications for a forward curved fan ?

Answer 12

Used for low pressure heating ventilating and air conditioning systems ranging from room air conditioners to residential furnaces

Question 13

What are the uses and applications for a forward curved fan ?

Answer 13

Used for low pressure heating ventilating and air conditioning systems ranging from room air conditioners to residential furnaces

Question 14

What are the uses and applications for a radial blade fan ?

Answer 14

For material handling high pressure industrial applications like saw dust

Question 15

What does cwbhd stand for ?

Answer 15

Clock wise bottom horizontal

Question 16

How is motor location determined ?

Answer 16

Facing drive side of the fan and designating the positions by letters w x y or z

Question 17

How much straight duct is required to achieve 100% effective duct length for systems with an airflow of 2500fpm or less ?

Answer 17

2.5 duct diameters

Question 18

What items would cause system resistance or pressure loss in an hvac system ?

Answer 18

Fittings coils dampers

Question 19

List 5 peices of info that can be found on a fan performance chart ?

Answer 19

Horse power
Volume
Static pressure
Rpm
System curves

Question 20

What damper is installed in branch fittings ?

Answer 20

Splitter dampers

Question 21

When would air extractors be used ?

Answer 21

When there is not adequate room to mount a splitter damper

Question 22

List 3 important functions of multi blade dampers ?

Answer 22

Control and mix outside air with return ,
Bypass heat transfer equitment ,control air qualities

Question 23

Name two styles of multi blade dampers ?

Answer 23

Parellel or opposed blade

Question 24

A 1000cfm of air is to be moved through a duct system with a total pressure of 0.4” wc which type of fan is best for this installations ?

Answer 24

Forward curved blade centrifugal fan

Question 25

Propeller disc fans are designed to ?

Answer 25

Have no duct at all

Question 26

The backward inclined airfoil fan is a refinement of the flat blades backward inclined centrifugal fan in what respect ?

Answer 26

It has better static efficiency It is quieter

Question 27

What type of fan blade arrangement is ussally used in air pollution control applications with high particulate loadings ?

Answer 27

Radial blades

Question 28

Which fan should never be used in a ductless system ?

Answer 28

Forward curved blade centrifugal fan

Question 29

In most cases what is the best fan to use on a blow pipe system for a sawmill ?

Answer 29

Radial bladed centrifugal fan

Question 30

Most upflow residential heating equitment uses a centrifugal fan in what position configuration?

Answer 30

Ccwubd

Question 31

The most accurate volume control of air is obtained by using a ?

Answer 31

Opposed blade damper

Question 32

An accepted method of determining the length of a splitter damper is ?

Answer 32

1.5 times the width of the small duct

Question 33

Which damper is generally used in locations where it is either fully open or fully closed ?

Answer 33

Pareellel blade damper

Question 34

These fans provide right angle airflow in a rectangular shape and are useful in applications such as air curtains over doorways ?

Answer 34

Cross flow fans

Question 35

Inlet box dampers supplied with parallel blades offer performance characteristics similar to inlet vane dampers (True or false )

Answer 35

True

Question 36

Parallel blade dampers are the best for modulating air flow ? (True or false)

Answer 36

False Either fully opened or fully closed

Question 37

Forward curved fans are common in wheel diameters up to ??

Answer 37

24”

Question 38

What type of fan has low noise emission and are suitable for restaurant exhaust systems or where air contains moisture or dust ?

Answer 38

Backward inclined blades