Humidification
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Which of the following is not a result of very low humidity?
a) Throat and nose membranes drying up
b) Static electricity build-up
c
c) Evaporation of moisture on the skin decreases
d) At sufficiently high room temperatures people still feel
cool
e) Wood furniture and floor squeaks and cracks
If air at 13 degrees C can hold a maximum of 0.0032 kg of
moisture per kilogram of air, what is the relative humidity
if the air contains 0.0015 kg of moisture per 1 kg of air?
a) 100%
b) 2.13%
d
c) 0.4%
d) 47%
e) 32%
The outside temperature 18 - 25 degrees C is saturated (Air
at -25 degrees C holds a maximum of 0.0005 kg of moisture/kg of
water). This air is drawn into the building and heated to 21 degrees
C (air at 21 degrees C holds a maximum of 0.015 kg
of moisture/kg of water). What is the relative humidity of
the air inside?
a) 3.3%
a
b) 0.015%
c) 0.5%
d) 10.6%
e) 4.5%
Humidity in the air
a) increases when the air temperature decreases
b) increases when the air pressure decreases
d
c) decreases when the air pressure increases
d) decreases when the air temperature decreases
e) remains constant with air temperature changes
Relative humidity is the amount of
a) moisture contained in the air compared to the maximum
amount of moisture the air is capable of holding at the
stated temperature
a
b) moisture contained in the air compared to the maximum
amount of moisture the air is capable of holding, air
temperature being irrelevant
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c) air contained in the air-moisture mixture compared to the maximum amount of air the air-mixture moisture is capable of holding
at the stated temperature
d) air compared to the amount of moisture in the air at any
temperature
e) moisture contained in the air at 0 degrees C
The purpose of humidification is to
a) add humidity to the air during the cooling season
b) add humidity to the air during the heating season
b
c) remove moisture from the air during the heating season
d) remove moisture from the air during the cooling season
e) add moisture to the air during the cooling season
Relative humidity
a) increases when the air temperature is raised without the addition of moisture to the air
b) remains the same when the air temperature is raised
c
c) decreases when the air temperature is raised without the
addition of moisture to the air
d) remains the same when the air temperature is lowered
e) decreases when the air temperature is lowered without the
addition of moisture to the air
Humidification in residences equipped with ducted warm air heating systems
a) is not necessary because the humidity does not change
with heating
b) requires separate humidifiers for each heated area
c) is accomplished by installing a second heating system, such as
hot water
e
d) is supplied sufficiently by normal living processes such
as cooking, washing, and breathing
e) is provided for by placing a single humidifier in the
furnace plenum or in the warm air duct
The residential humidifier which 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
d
b) welted element humidifier
c) steam grid humidifier
d) pan type humidifier
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e) power type humidifier
Which type of humidifier breaks water up into a mist or fog?
a) A bypass humidifier
b) A welted element humidifier
c
c) An atomizing humidifier
d) An air washing humidifier
e) A steam grid humidifier
Which of the following statements about Air washers is false?
a) Air washers can cool air.
b) Air washers can remove tobacco smoke.
b
c) Air washers can dehumidify air.
d) Air washers can heat air.
e) Air washers can clean air
To keep humidifiers in top 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
a) remove dirt
b) remove grease
d
c) remove soot
d) remove mineral salts
e) remove corrosion on the plate
Dehumidification occurs in an Air washer when which of the
following occurs?
a) If the level in the bottom tank drops lower than the
minimum level
b) If water temperature is heated above the dry bulb
temperature
c
c) If spray water is cooled to a temperature below the dew
point
d) Heating of the spray water
e) None of the above
It is not recommended to use an on-off switch for steam grid
humidifiers because
a) fogging would occur
e
b) overheating would occur
c) misting would occur
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d) wide fluctuations in relative humidity would occur
e) all of the above
Humidifying units which use a small fan to draw warmer air
from the furnace plenum or from the room, force the air
through the wetted pad, and return the air to the room, are
called
a) pan type humidifiers with plates
d
b) atomizing humidifiers
c) bypass type humidifiers
d) power type wetted element humidifiers
e) industrial pan type steam grid humidifiers
The types of humidifiers used for residential purposes are
a) air washers, wetted element, and atomizing
b) pan, atomizing, and air washers
d
c) pan, hot water, and air washers
d) atomizing, wetted element, and pan
e) pan, steam, and atomizing
Pan type humidifiers with plates
a) consist of rotating plates in a pan partially filled with
water
b) are placed in individual rooms to humidify the individual rooms
c) consist of a shallow pan, partially filled with water in
which absorbent plates are placed and the pan is
installed in the supply plenum of smaller warm air furnaces
c
d) consist of plates in a pan through which water is sprayed by a
spinning disc or cone
e) can be a power type or a bypass type
Wetted element humidifiers
a) are the same as pan type humidifiers
b) can be either the power type or the bypass type
c) have stationary plates placed in a tray and placed in
individual rooms
b
d) have a lower humidification rate than the pan type
humidifiers
e) are the same as the atomizing humidifiers
Atomizing humidifiers
a) break up the water for humidification into small
particles by either a spinning disc or spray nozzle and
are placed either in the warm air supply duct or in the
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area to be humidified
b) spray water through plates to atomize the water
c) spray water through rotating pads to atomize the water
a
d) can be either the power type or the bypass type
e) have a lower humidification rate than the pan type
humidifiers
A disadvantage of the atomizing humidifier is
a) it has a lower humidification rate than the pan type
humidifier
b) its evaporation plates clog up due to the salt left
behind after evaporation
e
c) it can be used only as an individual area or room
humidifier
d) its evaporation plates have to be replaced regularly
e) the salts that were in the water before atomization and
evaporation settle as white dust in rooms and ducts
Air washers used in air conditioning systems
a) only clean the air
b) only clean and cool the air
d
c) only humidify and dehumidify the air
d) humidify, heat, cool, dehumidify, and clean the air
e) only humidify, cool, and clean the air
Air washers used in air conditioning systems achieve heating and
humidification by
a) cooling the spray water to a temperature below the dew
point of the entering air
b) cooling the spray water to a temperature below the dry
bulb temperature
c
c) heating the spray water to a temperature above the dry
bulb temperature of the entering air
d) heating the entering air above its dry bulb temperature
e) cooling the entering air below its dry bulb temperature
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
b) cooling the spray water to a temperature below the dew
point temperature of the entering air
c) cooling the entering air below its dry bulb temperature
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d) heating the entering air above its dry bulb temperature
e) heating the spray water to a temperature above the dew
point temperature of the entering air
Which is not a method employed to maintain the desired temperature of the spray water in air washers used in air conditioning
systems?
a) an electric heater and fan
b) part of the spray water is recirculated and hot or cold
water is added as required
a
c) the spray water if recirculated through a heat exchanger and is
cooled by chilled water
d) the spray water is recirculated through a heat exchanger and
is heated by hot water
e) a heating or cooling coil is directly mounted in the sump
of the washer
Steam grid humidifiers used in air conditioning systems
achieve humidification by
a) the installation of a steam coil in the entering air
stream
b) the installation of a water coil in the entering air
stream
c
c) injecting steam in the supply air stream
d) injecting steam into the spray water of an air washer
e) injecting steam directly into the rooms to be humidified
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