Book 2 Chapter 10: Humidification

Question 1

Air that is at a higher temperature:
A) Causes floors to become squeaky
B) Will have greater static electricity than colder air
C) Can absorb more moisture than cooler air
D) Is always considered to be high pressure

Answer 1

C) Can absorb more moisture than cooler air

Question 2

The ideal relative humidity during cold weather:
A) Is above 40%
B) Is just below the point where condensation will develop on windows
C) Makes the internal temperature seem colder than it really is
D) Is the same for all buildings within a local area

Answer 2

B) Is just below the point where condensation will develop on windows

Question 3

A humidifier that makes use of the pressure difference between the supply and return plenum is the:
A) Bypass type
B) Power type
C) Pan type
D) Atomizing type

Answer 3

A) Bypass type

Question 4

An air washer is installed on the suction side of the fan to:
A) Allow the air to be heated as well dehumidified
B) Allow the air to be cooled as well as humidified
C) Keep the pressure below atmospheric to prevent water leakage through joints
D) Allow the water to be recirculated

Answer 4

C) Keep the pressure below atmospheric to prevent water leakage through joints

Question 5

The residential humidifier is commonly used in the supply plenum of smaller warm air furnaces and consists of a shallow tray partially filled with water is called a:
A) Bypass humidifier
B) Steam grid humidifier
C) Wetted element humidifier
D) Power type humidifier
E) Pan type humidifier

Answer 5

E) Pan type humidifier

Question 6

To prevent condensation on windows when the temperature outside is -29ºC the relative humidity should be less than:
A) 40%
B) 35%
C) 20%
D) 25%
E) 30%

Answer 6

C) 20%

Question 7

Which of the following is not a result of very low humidity?
A) Evaporation of moisture on the skin decreases
B) Wood furniture and floor squeaks and cracks
C) Static electricity buildup
D) Throat and nose membranes drying up
E) At sufficiently high room temperatures people still feel cold

Answer 7

A) Evaporation of moisture on the skin decreases

Question 8

Air washers used in air conditioning systems achieve cooling and dehumidification by:
A) Heating the spray water to a temperature above the dry bulb temperature of the entering air
B) Heating the entering air above its dry bulb temperature
C) Cooling the spray water to a temperature below the dew point temperature of the entering air
D) Heating the spray water to a temperature above the dew point temperature of the entering air
E) Cooling the entering air below its dry bulb temperature

Answer 8

C) Cooling the spray water to a temperature below the dew point temperature of the entering air

Question 9

Pan type humidifiers with plates:
A) Consist of plates in a pan through which water is sprayed by a spinning disc or cone
B) Consists of a shallow pan, partially filled with water in which absorbent plates are placed
C) Can be either a power type or a bypass type
D) Are placed in individual rooms to humidify the individual rooms
E) Consist of rotating plates in a pan partially filled with water

Answer 9

B) Consists of a shallow pan, partially filled with water in which absorbent plates are placed

Question 10

In order to keep humidifiers in top working condition the plates of plate type units should be cleaned by soaking them in a slightly acidic solution and then washing them in soapy water to remove:
A) Mineral salts
B) Grease
C) Soot
D) Corrosion on the plate
E) Dirt

Answer 10

A) Mineral salts

Question 11

When air temperature is raised without the addition of moisture:
A) The relative humidity rises
B) There is less moisture in the air
C) There is more moisture in the air
D) The air has less capacity to hold moisture
E) The relative humidity falls

Answer 11

E) The relative humidity falls

Question 12

From a health standpoint, relative humidity should be controlled in the range of:
A) More than 50%
B) Less than 50%
C) 35-50%
D) 54-70%
E) 10-35%

Answer 12

C) 35-50%

Question 13

An air washer is used to spray water into the air for humidification and can also be used to:
A) Heat
B) Dehumidify
C) Clean the air
D) Cool
E) All answers are correct

Answer 13

E) All answers are correct

Question 14

One of the wetted element humidifiers group is the ________ type.
A) Bypass
B) Steam
C) Pan
D) Wet
E) Spray

Answer 14

A) Bypass

Question 15

The steam pressure on a steam grid humidifier should be in the range of:
A)25kPa to 45kPa (3.6 to 6.5psi)
B) 20kPa to 30kPa (2.9 to 4.4psi)
C) 30kPa to 60kPa (4.4 to 8.7psi)
D) 40kPa to 55kPa (5.8 to 8psi)
E) 35kPa to 70kPa (5.1 to 10.2psi)

Answer 15

E) 35kPa to 70kPa (5.1 to 10.2psi)

Question 16

When the air washer is used for dehumidification, the spray water must be _______ temperature of the entering air.
A) Cooled below the wet bulb
B) Cooled below the dew point
C) Heated above the dew point
D) Heated above the dry bulb
E) Cooled below the dry bulb

Answer 16

B) Cooled below the dew point

Question 17

An air washer is installed on the suction side of the fan so as to:
A) Add moisture to the air
B) Avoid leakage of water through the joints
C) Add sensible heat to the air
D) Avoid leakage of air through the joints
E) Add latent heat to the air

Answer 17

B) Avoid leakage of water through the joints

Question 18

The humidification process refers to adding ________ to the air.
A) Enthalpy
B) Steam
C) Temperature
D) Heat
E) Water vapour or moisture

Answer 18

E) Water vapour or moisture

Question 19

Calculate the relative humidity of a sample of air that at 21ºC (70ºF) holds 0.014kg (0.031lbs) of moisture if the maximum that it can hold at this temperature is 0.015kg(0.033lb).
A) 25.8%
B) 6.7%
C) 0.33%
D) 93.3%
E) 10.7%

Answer 19

D) 93.3%

Question 20

Calculate the relative humidity of a sample of air that at 21ºC (70ºF) holds 0.005kg(0.011lb) of moisture if the maximum that it can hold at this temperature is 0.015kg (0.033lb).
A) 10.7%
B) 33.3%
C) 6.7%
D) 25.8%
E) 93.3%

Answer 20

B) 33.3%

Question 21

The steam heated pan humidifier offers high capacity and accurate humidity control if used with a modulating control valve and steam pressure not exceeding:
A) 160kPa (23.2psi)
B) 130kPa (19psi)
C) 10kPa (1.5psi)
D) 103kPa (15psi)
E) 50kPa (7.3psi)

Answer 21

D) 103kPa (15psi)

Question 22

One of the types of humidifiers used for residential purposes is the _______ humidifier.
A) Pot
B) Wetted element
C) Air washer
D) Dry element
E) Steam

Answer 22

B) Wetted element

Question 23

One of the wetted element humidifiers group is the _______ type.
A) Spray
B) Power
C) Wet
D) Pan
E) Steam

Answer 23

B) Power