Unit 35: Lab Work - Comfort and Psychrometric

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

100

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

100%.

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

13%.

The density of water is ____.

62.4 lb/ft3

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

nitrogen

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

oxygen starved and stagnant

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

14.0 ft3/lb

Determine the airflow through a furnace that is producing 60,000 Btu/h of heat when the return air temperature is 72°F and the supply air temperature is 130°F.

958 cfm

The average core body temperature is

98.6

Calculate the volume of a house that is 3500 ft2 with a 9-foot ceiling.

31,500 ft3

Determine the total heat content of an outdoor air sample if the sample's dry-bulb temperature is 93°F and its wet-bulb temperature is 74°F.

37.7 Btu/lb.

Determine the dew point temperature of an air sample if the sample's dry-bulb temperature is 70°F and its wet-bulb temperature is 61°F.

55ºF.

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.

75

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

8

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

Evaporation.

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

False

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

True

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.

True

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

enthalpy

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

grains

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

humidity

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

determine combinations of temperature and humidity to produce comfort in summer and winter

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

ventilation

The density of air is the ____.

weight of the air per cubic foot

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

40°F.

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

relative humidity

Name the four factors that affect comfort.

[temperature ] [humidity] [air cleanliness ] [air movement ]

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

around doors and windows

The dry-bulb temperature is the ____.

sensible heat level of the air

The reading from a wet-bulb thermometer ____.

takes into account the moisture content of the air

The dew-point temperature is the ____.

temperature at which moisture begins to condense out of the air

Comfort can be described as the gentle balance between ____.

temperature, humidity, air movement, and air cleanliness

The wet-bulb depression is ____.

the difference between dry- and wet-bulb temperatures