Deck 35: Comfort and Psychrometrics

Question 1

A small amount of air is induced from the outside into the conditioner to keep the air from becoming ____.

A) too humid
B) superheated
C) oxygen starved and stagnant
D) too dry

Answer 1

C

Question 2

The generalized comfort chart can be used as a basis to ____.

A) determine combinations of temperature and humidity to produce comfort in summer and winter
B) study air and its properties
C) determine the amount of fresh air make up necessary for comfort
D) None of the above.

Answer 2

A

Question 3

Introduction of forced ventilation in the winter heating season helps to raise the humidity level.

Answer 3

False

Question 4

If the wet-bulb and dry-bulb temperature are both 80°F, what is the humidity?

A) 0%.
B) 35%.
C) 70%.
D) 100%.

Question 5

Comfort can be described as the gentle balance between ____.

A) temperature, humidity, air movement, and air cleanliness
B) air velocity, air cleanliness, humidity, and air movement
C) air speed, air velocity, temperature, and humidity
D) acceleration, air cleanliness, filtration, and humidity

Question 6

The density of air is the ____.

A) amount of moisture in the air
B) amount of movement in the air per cubic foot
C) weight of the air per cubic foot
D) combination of the temperature and pressure of the air

Question 7

The reading from a wet-bulb thermometer ____.

A) is the same as the wet-bulb depression
B) is the saturation pressure
C) takes into account the moisture content of the air
D) is always higher than the dry-bulb temperature

Question 8

Infiltration is the term used when referring to the air entering a structure ____.

A) through an air make-up unit
B) around doors and windows
C) through ventilation
D) because of street traffic

Question 9

If the dry-bulb temperature is 93°F and the wet-bulb temperature is 60°F, what is the specific volume of the air?

A) 14.0 ft³/lb
B) 14.0 lb/ft³
C) 12.0 lb/ft³
D) 12.0 ft³/lb

Question 10

Of the heat produced in the human body, which is by perspiration?

A) Conduction.
B) Convection.
C) Radiation.
D) Evaporation.

Question 11

What is the relative humidity if the dry-bulb temperature is 100º F and the wet-bulb temperature is 65°F?

A) 13%.
B) 28%.
C) 43%.
D) 58%.

Question 12

Typically, when the body is at rest (sitting) and in surroundings of ____________________°F and 50% humidity with a slight air movement, the body is close to being comfortable.

Question 13

The dry-bulb temperature is the ____.

A) same as the wet-bulb temperature
B) total of the sensible and latent heat
C) sensible heat level of the air
D) sensible heat less the humidity

Question 14

The human body is comfortable when the heat produced in the body is equal to the heat lost to the surroundings.

Question 15

The dew-point temperature is the ____.

A) temperature when the air is saturated with moisture
B) temperature at which moisture begins to condense out of the air
C) difference between the dry-bulb and wet-bulb temperatures
D) temperature of the air at 50% relative humidity

Question 16

What is the dew-point temperature if the wet-bulb temperature is 65°F and the dry-bulb temperature is 100°F?

A) 40°F.
B) 50°F.
C) 60°F.
D) 70°F.

Question 17

The density of water is ____.

A) 61.3 lb/ft³
B) 62.0 lb/ft³
C) 62.4 lb/ft²
D) 62.4 lb/ft³

Question 18

The average core body temperature is ____________________°F.

Question 19

The rate at which water will evaporate from the wick on the wet-bulb thermometer is determined by the moisture content of the surrounding air.

Question 20

The wet-bulb depression is ____.

A) the difference between dry- and wet-bulb temperatures
B) the same as the wet-bulb temperatures
C) the same as the dry-bulb temperatures
D) when the air is saturated with moisture

Question 21

The closer the wet-bulb and dry-bulb temperatures are to each other, the higher the ____________________.

Question 22

The moisture content in air (humidity) is measured by weight and expressed in pounds or ____________________.

Question 23

When the dry-bulb and wet-bulb temperatures are the same, the relative humidity of the air is ____________________%.

Question 24

If the dry-bulb temperature is 76°F and the wet-bulb temperature is 68°F, the wet-bulb depression is ____________________°F.

Question 25

Air consists of approximately 78% ____________________, 21% oxygen, and 1% other gases.

Question 26

Under what conditions can the wet-bulb temperature be higher than the dry-bulb temperature?

Question 27

When fresh air is introduced through the air handling system, the process is called fresh air intake, or ____________________.

Question 28

Explain how a wet-bulb thermometer works.

Question 29

Why must the thermometers in a sling psychrometer be swung in order to obtain the readings?

Question 30

The ____________________ of air is the measure of heat content in Btu per pound of air.

Question 31

How can the cost of heating a home in the winter be lowered, and still have comfortable conditions in the home?

Question 32

Water, in the form of low-pressure vapor, is suspended in the air and is called ____________________.

Question 33

What will happen if a technician uses a sling psychrometer that has a perfectly dry wick on the wet-bulb thermometer?

Question 34

How does air movement improve comfort?

Question 35

The air leaving an evaporator has a dry-bulb temperature of 85°F and a wet-bulb temperature of 65°F. The air entering the evaporator has a dry-bulb temperature of 95°F and a wet-bulb temperature of 75°F. How many grains of moisture per pound of dry air were removed by the evaporator?