Chapter 127

Question 1

List five different devices used to distribute the air of an air conditioning system

Answer 1

ducts, grilles, diffusers, dampers and louvres

Question 2

The energy imparted to the air by a fan is in the form of what energy?

Answer 2

potential

Question 3

With what device can you measure potential energy created by fans?

Answer 3

manometers

Question 4

What are the three pressures created by a fan?

Answer 4

static, velocity and total pressure

Question 5

How can static pressure be measured?

Answer 5

connecting the manometer at right angles to the duct

Question 6

________ is caused by the impact of air flowing through a duct; it is felt only by the surfaces the air actually strikes

Answer 6

velocity

Question 7

By connecting one end of the manometer at right angles to the duct wall and the other end with opening facing the air flow what pressure is being measured?

Answer 7

velocity

Question 8

What happens to the pressures when the air goes through a converging section?

Answer 8

velocity pressure increases, static pressure decreases, total pressure stays the same.

Question 9

What happens to the pressures when the air goes through a divergying section?

Answer 9

velocity pressure decreases, static pressures increases, total pressure stays the same

Question 10

What are the two general groups of fans?

Answer 10

Centrifugal and axial flow

Question 11

The air flows axially through the impeller

Answer 11

Axial flow fan

Question 12

the air flows radially through the impeller

Answer 12

Centrifugal fan

Question 13

What are the standard classes of air?

Answer 13

21 degrees celsius, 101.3 kPa, 1.2 kg/m^3

Question 14

Four types of centrifugal fans:

Answer 14

Straight, backward inclined blades, forward curved blades, backward inclined airfoil blades

Question 15

Three types of Axial fans:

Answer 15

Propeller fan, Tube axial fan, Vane Axial fan

Question 16

These are normally used on smaller sized air moving equipment

Answer 16

Direct drives

Question 17

These are used on most air conditioning, heating and ventilation applications

Answer 17

V-Belt Drives

Question 18

Control of the static pressure and horsepower requirements at a given speed is obtained by using:

Answer 18

Variable inlet vane control

Question 19

In order to convert static pressure to velocity pressure in an air distribution system it is necessary to:

Answer 19

decrease the cross-sectional area of duct

Question 20

The propeller axial fan is used for:

Answer 20

high capacity, low pressure applications

Question 21

Has low rotation speed:

Answer 21

forward curve

Question 22

Coupling guards are used on?

Answer 22

direct drives

Question 23

Has higher losses in ducts than the centrifugal fan

Answer 23

axial flow fan

Question 24

Mostly used for high capacity, high pressure application

Answer 24

backward inclined airfoil fans

Question 25

Velocity pressure is converted into static pressure in a centrifugal fan with use of an?

Answer 25

Volute shape