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Title: Modern Refrigeration and


1
Modern Refrigeration and Air Conditioning
Althouse Turnquist Bracciano
PowerPoint Presentation by Associated
Technical Authors
PublisherThe Goodheart-Willcox Company,
Inc.Tinley Park, Illinois
2
Chapter 19
Fundamentals of Air Conditioning
3
Learning Objectives
  • Explain the principles of air conditioning.
  • Discuss the physical principles of air movement
    and humidity.
  • List the important factors involved in the
    operation of an air conditioning system.
  • List and explain the factors of air conditioning
    that affect comfort and health, and the methods
    of conditioning air for these purposes.

4
Learning Objectives
  • Understand the use for various instruments, such
    as psychrometers, dry bulb thermometers,
    hygrometers, pitot tubes, recorders, manometers,
    and barometers.
  • Read and interpret psychrometric charts and
    scales.
  • Follow approved safety procedures.

5
Chapter 19
AIR MOVEMENT AND MEASUREMENT MODULE
6
Definition of Air Conditioning
19.1
  • ASHRAE defines air conditioning as the process
    of treating air so as to control simultaneously
    its temperature, humidity, cleanliness, and
    distribution to meet the requirements of the
    conditioned space.
  • Important actions involved in operation of an air
    conditioning system include
  • Temperature control.
  • Humidity control.
  • Air filtering, cleaning, and purification.
  • Air movement and circulation.

7
Definition of Air Conditioning continued
19.1
  • Winter heating
  • Requires automatic control of a heating source to
    maintain the desired room temperatures.
  • Humidity control usually requires the addition of
    moisture by a humidifier.
  • Summer cooling
  • Requires automatic control of an air conditioning
    system to maintain the desired room temperatures.
  • Humidity control requires dehumidifiers, which
    pass air to be cooled over cold evaporator
    surfaces.

8
Definition of Air Conditioning continued
19.1
  • Air filtering requirements are the same for
    winter or summer.
  • Filters may be made of very fine porous
    substances or activated carbon and electrostatic
    precipitators.

9
Air-Atmosphere
19.2
  • Air is an invisible, odorless, tasteless mixture
    of gases that surrounds the earth.
  • The air surrounding the earth is called the
    atmosphere.
  • Extends from the surface to 400 miles above the
    earth.
  • The layer closest to earthfrom sea level to
    30,000'is called the lower atmosphere.
  • The troposphere is the layer from 30,000' to
    50,000'.
  • The layer from 50,000' to 200 miles is called the
    stratosphere.
  • The layer beyond 200 miles called the ionosphere.

10
Air-Atmosphere continued
19.2
  • Air is a mixture of oxygen, nitrogen, carbon
    dioxide, sulfur dioxide, and water vapor. It
    contains a very small percentage of rare gases.

11
Oxygen
19.2
  • The atmosphere is approximately 23 oxygen by
    weight.
  • Readily combines with many substances.
  • Fuels burning combine their carbon and hydrogen
    with oxygen to form carbon dioxide and water.
  • Replenished by plants, which absorb carbon
    dioxide and release oxygen.

12
Nitrogen
19.2
  • Three-fourths of the atmosphere consists of
    nitrogen.
  • A gaseous element that does not combine readily
    with other substances.
  • When combined with other elements, the result is
    usually unstable.
  • Combined commercially with hydrogen to form
    ammoniathe basis of most fertilizers and an
    important refrigerant (R-717).

13
Carbon Dioxide
19.2
  • Makes up 0.03 to 0.04 of atmosphere.
  • Combination of carbon and oxygen.
  • Absorbed by plants and is a building block in
    their cell development.

14
Hydrogen
19.2
  • Very light gas. Does not show in weight
    percentage.
  • Present in most fuels.
  • When burned combines with oxygen to form water.

15
Sulfur Dioxide
19.2
  • Most common gaseous contaminant.
  • Formed by combustion of fuels that contain
    sulfur.
  • Large power plants have facilities for removing
    sulfur from fuel sources and sulfur dioxide from
    stack gases.

16
Water Vapor (Moisture)
19.2
  • The amount of water vapor in the atmosphere
    varies with temperature.
  • Indicated in terms of relative humidity.

17
Rare Gases
19.2
  • Make up from 0.9 to 1.3 of the atmosphere by
    weight.
  • Includes neon, argon, helium, krypton, and xenon.

18
Physical Properties of Air
19.3
  • Air has a weight, density, temperature, specific
    heat, and heat conductivity.
  • In motion, air has momentum and inertia.
  • Air holds substances in suspension and in
    solution.
  • Air pressure at the earths surface is due to the
    weight of air above the earth.
  • Air pressure decreases as altitude increases.
  • Air presses against the earth at sea level with
    pressure of 14.7 psia (101.4 kPa).

19
Physical Properties of Air continued
19.3
  • Density of air varies with atmospheric pressure
    and humidity.
  • Air temperatures may be measured in Fahrenheit or
    Celsius.
  • When measuring low temperatures, thermocouple
    thermometers or resistance temperature detectors
    are used.
  • Thermocouple thermometers, thermistor
    thermometers, and pyrometers may be used for high
    temperatures.

20
Physical Properties of Air continued
19.3
  • Specific heat of air is the amount of heat
    required to raise the temperature of one pound of
    air by one degree Fahrenheit, or one kilogram of
    air by one degree Celsius. The specific heat of
    air at sea level is 0.24 Btu per pound (0.557
    kJ/kg).
  • Air is a poor conductor of heat. Air spaces are
    often used for insulating purposes.

21
Humidity
19.3.1
  • Presence of moisture or water vapor in air. The
    amount of moisture that air will hold depends on
    the air temperature. Warm air holds more moisture
    than cold air.
  • The level of humidity affects the rate of
    evaporation of perspiration from your body. Dry
    air causes rapid evaporation moist air prevents
    it.
  • Moisture is in vapor form and invisible.

22
Relative Humidity
19.3.1
  • Term used to express amount of moisture in given
    sample of air. It is compared with the amount of
    moisture that the air would hold if totally
    saturated at the temperature of the sample.
  • Stated in percentage.
  • A water vapor saturation curve is a graph showing
    the amount of water air can hold at different
    temperatures.

23
Relative Humidity continued
19.3.1
  • In the graph shown, the line from A to B
    represents what happens when saturated air is
    warmed. Point D represents what happens when
    saturated air is cooled. The distance from D to E
    represents moisture condensed out of the air.
  • Point F on the graph is typical winter condition
    outdoors.

24
Indicators of Low Humidity
19.3.1
  • Low humidity is indicated by
  • Noticeable electrostatic energy.
  • Furniture joints shrink and become loose.
  • Surface of the skin and membranes in the nose
    become dry.

25
Humidity Measurement
19.3.1
  • A hygrometer is an instrument used to measure the
    moisture content in air.
  • Hygrometers contain a moisture-absorbing
    substance that changes shape or size due to
    relative humidity.

26
Humidity Measurement continued
19.3.1
  • This relative humidity meter contains a
    microprocessor. It measures the relative humidity
    and temperature. Other data is calculated from
    the measurements.

27
Humidity Measurement continued
19.3.1
  • This electronic hygrometer measures temperature,
    relative humidity, and dew point.
  • Reading appears on the display panel.

28
Humidity Measurement continued
19.3.1
  • A seven-day temperature and humidity chart
    recorder indicates moisture and temperature over
    time. A psychrometric chart is used to determine
    relative humidity.
  • Desiccants have a moisture-absorbing ability.
    Common desiccants are activated alumina, silica
    gel, calcium sulfate, and zeolites. Instruments
    are often packaged with a desiccant to any absorb
    moisture inside the container.

29
Humidity Controls
19.3.1
  • An important factor in air conditioning.
  • Operate during the winter heating season to add
    moisture to the air.
  • Operate in the summer to remove moisture from the
    air. Operates an air bypass which varies airflow
    over the evaporators.
  • Controls operate electrically to regulate
    solenoid valves or dampers.

30
Humidity Controls continued
19.3.1
  • Thermo-humidigraphs (temperature and humidity
    recorders) may be fitted with alarms that sound
    if humidity does not remain at the proper level.

31
Air Temperature
19.3.2
  • The behavior of air varies with temperature. The
    higher the temperature, the greater its ability
    to hold moisture.
  • In air conditioning, air temperature is indicated
    by the dry bulb temperature. This is the
    temperature normally reported.

32
Air Temperature continued
19.3.2
  • Wet bulb temperature is measured by placing a
    moist wick over the thermometer bulb.
  • Evaporation of moisture from wick will lower the
    thermometer reading.
  • If the surrounding air is dry, evaporation from
    the wick is rapid. If the air is moist,
    evaporation is slower.

33
Air Temperature continued
19.3.2
  • If air is saturated with moisture, no water will
    evaporate wet and dry bulb temperatures are
    identical.
  • The wet bulb reading depends on how fast the air
    passes over the bulb. Speeds up to 5000 ft./min.
    (60 mi./hr.) are best. The wet bulb should be
    protected from radiating surfaces to avoid errors
    in the reading.

34
Psychrometric Propertiesof Air
19.3.3
  • Psychrometry is the science and practice of
    dealing with air mixtures and their control.
  • Computers are used to determine and control the
    condition of air in large building complexes.

35
Psychrometric Propertiesof Air continued
19.3.3
  • Psychrometry deals with the specific heat of dry
    air and its volume, as well as the heat of water,
    heat of vaporization or condensation, and
    specific heat of steam in reference to moisture
    mixed with air.
  • Tables, graphs, and charts have been developed to
    show pressure, temperature, heat content
    (enthalpy), volume of air, and steam content of
    air. A pressure of 29.92" Hg (76 cm Hg) is used
    as standard atmospheric pressure.

36
Psychrometer
19.3.3
  • A sling psychrometer is used to whirl pair of
    thermometers, one dry bulb and one wet bulb. The
    wick is saturated. When the mercury stops
    dropping, read the two thermometers.
  • Place the wet bulb temperature over the dry bulb
    temperature scale on a slide rule. The arrow on
    the scale indicates the relative humidity.

37
Psychrometer continued
19.3.3
  • Battery-operated digital sling psychrometers are
    available. A fan draws air over the thermometer
    sensing bulbs.

38
Psychrometric Chart
19.3.3
  • Graphs the properties (temperature, relative
    humidity, etc.) of air.
  • Used to determine how these properties vary as
    amount of moisture in the air changes.

39
Psychrometric Chart
19.3.3
  • The horizontal scale (abscissa) on a basic
    psychrometric chart is the dry bulb temperature.
  • The vertical scale (ordinate) on a basic
    psychrometric chart represents water vapor
    pressure.

40
Psychrometric Chart continued
19.3.3
  • Psychrometric chart showing constant dry bulb
    temperature (red line). This is always a vertical
    line.

41
Psychrometric Chart continued
19.3.3
  • Psychrometric chart showing line of constant wet
    bulb temperature (line of constant enthalpy).

42
Psychrometric Chart continued
19.3.3
  • Psychrometric chart showing line of constant
    water vapor pressure (lb. water/lb. dry air or
    water grains/lb. dry air).

43
Psychrometric Chart continued
19.3.3
  • Psychrometric chart showing line of constant
    relative humidity (). The 100 relative humidity
    line is also known as the dew point or saturation
    temperature line.

44
Psychrometric Chart continued
19.3.3
  • Note Each point on the psychrometric chart
    represents air at a specific set of conditions.
  • Remember The warmer the air, the more moisture
    it will hold. As pressure is reduced, air absorbs
    more moisture.

45
Using the Psychrometric Chart
19.3.3
  • Psychrometric charts are helpful when
    troubleshooting equipment. The chart can show
    what is occurring during a specific heating,
    ventilating, and air conditioning process.
  • Psychrometric charts give a considerable range of
    temperature and humidity conditions.
  • Humans are comfortable in a certain range of
    conditions. Most people are comfortable in an
    atmosphere with relative humidity between 30 and
    70 and temperatures between 70ºF and 85ºF (20ºC
    to 30ºC).
  • HVAC systems modify conditions through heating,
    cooling, humidification, and dehumidification.

46
Using the Psychrometric Chartcontinued
19.3.3
  • These processes are modeled on the psychrometric
    chart.
  • Point A shows dry bulb temperature of 40ºF and a
    relative humidity of 30.
  • Point B shows the desired condition 75ºF and 50
    relative humidity.
  • The HVAC system must provide processes
    represented by colored lines connecting points A
    and B.

47
Using the Psychrometric Chartcontinued
19.3.3
  • A psychrometric chart can be used to plot the
    actions of evaporators, heaters, and chillers in
    an HVAC system.

48
Dew Point
19.3.4
  • Dew point is the temperature below which water
    vapor in the air will start to condense.
  • The 100 humidity point.
  • Relative humidity of a sample of air is
    determined by its dew point.

49
Dew Point continued
19.3.4
  • Procedure
  • Place a volatile fluid in a bright metal
    container.
  • Stir the fluid with an air aspirator.
  • Place a thermometer in fluid to indicate the
    temperature of both the fluid and container.
  • While stirring, a mist or fog appears on the
    outside of the metal container.
  • The temperature at which this fog appears is the
    dew point.
  • Caution Volatile fluids that are also flammable
    or toxic must not be used for this experiment.

50
Dew Point continued
19.3.4
  • This instrument is used to determine dew point.
    It can measure dew points from room temperature
    to 80ºF (62ºC).

51
Dew Point continued
19.3.4
  • Procedure
  • A sample of air is pumped into the observation
    chamber of the instrument.
  • Pressure is above atmospheric.
  • Pressure ratio gauge adjusts for this pressure.
  • Valve is manipulated to exhaust the air.
  • Observation window will indicate a fog when the
    sample is cooled to its dew point. The window is
    lighted and a sunbeam effect is noted if fog
    exists.

52
Dew Point continued
19.3.4
  • Procedure (continued)
  • Pressure ratio determines the dew point
    temperature.
  • During the winter heating season, an outside
    window offers good example of dew point. The
    surface temperature of the glass will cause
    condensation at certain levels of humidity.

53
Vapor Barriers
19.4
  • Moisture-proof materials, such as aluminum foil
    and plastic sheeting, are used in home
    construction to form a vapor barrier.
  • Water vapor is prohibited from passing through
    the walls and toward surfaces where it might
    condense.
  • Vapor barriers should always be installed on the
    warm side of the insulation, toward the heated
    space.
  • Peeling exterior paint near the kitchen or
    bathroom areas indicates the lack of a proper
    vapor barrier. Moisture from the area travels
    through the walls. When it contacts the cold
    undersurface of the paint, droplets of water are
    formed, which cause paint to peel.

54
Air Movement
19.5
  • Air movement affects comfort.
  • Cool, dry air circulated past a warm body speeds
    heat flow from the body. Evaporation increases.
    This cools the body.
  • Wind velocity and relative humidity may cause
    wind chill.
  • If air inside a conditioned space moves too fast
    (a draft), it feels uncomfortable.
  • If air inside a conditioned space moves too
    slowly, air becomes stale and lacks oxygen.

55
Air Velocity Measurement
19.5.1
  • Outside air velocity (wind) is measured in miles
    per hour (mph) or knots.
  • Interior air velocity is usually expressed in
    feet per minute (fpm).
  • To calculate volume of air flowing through a duct
    in cubic feet per minute (cfm), multiply air
    velocity by the cross-sectional area of the duct.
  • If air flows more than 15' to 20' per minute (4.5
    to 6 m/min.), occupants will feel a draft.

56
Air Velocity Measurement continued
19.5.1
  • Methods of measuring air velocity include
  • Anemometer (rotating).
  • Anemometer (hot wire).
  • Velocimeter (swinging vane).
  • Velocity pressure (manometer-pitot tube).
  • Rotating anemometer, direct-reading velocimeter,
    and pitot tube are not accurate at very low air
    velocities.

57
AnemometerRotating and Hot Wire
19.5.1
  • Consists of small propeller placed in air stream
    that revolves as air flows past the blades. The
    instrument connected to propeller measures the
    flow. There is a start lever and a return-to-zero
    lever.

58
AnemometerRotating and Hot Wire continued
19.5.1
  • Operation
  • Place in the air stream at a right angle to the
    airflow.
  • Allow it to reach constant speed, about one
    minute. Then, trip registering mechanism.
  • At same time, start a stopwatch. Record the
    reading and time.
  • From these data, compute the velocity of air in
    feet per minute.
  • Divide number of feet by elapsed time.
  • Take several readings and compute average for
    greater accuracy.

59
AnemometerRotating and Hot Wire continued
19.5.1
Anemometer that reads air velocity in cfm.
60
AnemometerRotating and Hot Wire continued
19.5.1
  • Operation of the anemometer in the previous
    slide
  • The dial will indicate airflow from HVAC grilles
    in cubic feet per minute (cfm).
  • Operator can calculate number of Btus going into
    the conditioned space through each grille.
  • Airflow is multiplied by the appropriate
    temperature factor.
  • The device takes account of grille area entered
    as data into the instrument.

61
Portable Air Velocity Meter
19.5.1
  • Depends on the cooling effect of air flowing over
    an electrically heated wire.

62
Portable Air Velocity Meter continued
19.5.1
  • Operation of the meter shown
  • Incoming air pushes on a small vane.
  • The vane tilts at different angles as air
    velocity increases.
  • The instrument is put directly in the air stream.

63
Direct Reading Airflow Meter
19.5.1
  • Measures air velocities in main ducts and branch
    ducts.
  • Used to balance air distribution systems.
  • Calibrated for use at temperature of 68ºF.
    Corrections must be made if duct temperature is
    not 68ºF.

64
Direct Reading Airflow Meter continued
19.5.1
  • Formula for correction



(460) T
X instrument reading
fpm
(460) 68
T Fahrenheit temperature of the air in the duct
65
Velocity-Pressure (Pitot Tube)
19.5.1
  • Pitot tube is used to measure air velocity.

66
Velocity-Pressure (Pitot Tube) continued
19.5.1
  • Operation
  • Manometer must be mounted level to obtain
    accurate readings.
  • A rotating turbulent airflow affects the
    measurement of true pressures.
  • Use a pitot tube only where the duct is very
    long. The length of the duct downstream of the
    measuring location should be minimum of 10 times
    the duct diameter.

67
Velocity-Pressure (Pitot Tube) continued
19.5.1
  • Operation (continued)
  • For precise measurements, air-straightening vanes
    should be located upstream of the pitot tube.
  • Air contacting the nose of the pitot tube creates
    a total pressure.
  • The outer tube with holes on its side measures
    static pressure.

68
Velocity-Pressure (Pitot Tube) continued
19.5.1
  • Operation (continued)
  • When the two pressures are connected to the end
    of the manometer, difference is
    velocity-pressure.
  • This pressure difference is measured in inches of
    water.

69
Velocity-Pressure (Pitot Tube) continued
19.5.1
Inclined manometer used with pitot tube.
70
Velocity-Pressure (Pitot Tube) continued
19.5.1
  • Formula
  • Velocity (V) 4005 X Square root of
    velocity pressure in inches of water (Vp)
  • V 4005 Ö Vp

71
Velocity-Pressure (Pitot Tube) continued
19.5.1
  • The constant 4005 is for standard conditions.
    Constant changes are based on the density of air.

72
Velocity-Pressure (Pitot Tube) continued
19.5.1
  • For accuracy in velocity readings, take several
    readings in various parts of the duct. Average
    the readings.
  • Sensor locations for measuring velocity for both
    rectangular and circular ducts are shown on the
    next slide.

73
Velocity-Pressure (Pitot Tube) continued
19.5.1
74
Ventilation
19.5.2
  • Changing air in a building.
  • To quickly replace all air in confined space,
    open all windows and doors and flush the space
    completely with 100 outside air.
  • Most heating systems slowly exhaust some of the
    inside air and bring in fresh air from the
    outside.
  • Movement of air in a home also occurs through
    cracks around windows and doors and each time
    doors are opened.

75
Ventilation continued
19.5.2
  • Air tends to enter a building on the upwind side
    and leave the building on the downwind side.
  • Warm air is lighter than cold air and rises in a
    room. In buildings of more than one story, warm
    air rises from lower to upper floors. Pressure is
    created causing some warm air to escape through
    upper surfaces of building. This air is replaced
    by cold air entering the lower levels.
  • During summer air conditioning, cold air flows
    downward and may leave building at lower levels.
    Cold air is replaced by warmer air entering at
    upper levels. Replaced air is called make-up
    air.

76
Ventilation continued
19.5.2
  • A structure that keeps the inside air pressure
    slightly above atmospheric pressure has a
    positive pressure.
  • A structure that maintains an inside air pressure
    that is slightly below atmospheric pressure has a
    negative pressure.
  • Fuel-burning furnaces, stoves, and fireplaces
    operating in winter produce negative pressure.
    Positive pressure can be maintained only if fan
    or blower is used to bring in fresh air.

77
Climate
19.6
  • Includes temperature, humidity, sunshine,
    pressure, and air movement.
  • There is a relationship between comfort and the
    temperature, humidity, and air movement
    conditions.

78
Climate
19.6
79
Climate continued
19.6
  • Increasing movement of the air has a cooling
    effect on the body. If air movement is over 15 to
    20 fpm, a temperature increase may be needed to
    maintain a comfortable indoor climate.
  • Weather is the conditions in the atmosphere
    including temperature, wind velocity and
    direction, clouds, moisture, and atmospheric
    pressure.
  • Weather affects the need for, and requirements
    of, air conditioning.

80
Air Temperature
19.6.1
  • Varies in the United States from a low of about
    55ºF (48ºC) to a high of around 120ºF (49ºC).
  • Normal, desirable temperature is 72ºF (22ºC).
  • Normally, temperature of human body is 98.6ºF
    (37ºC). Skin temperature is about 91ºF (33ºC).
  • Air is heated or cooled to maintain comfortable
    temperatures.
  • The specific heat of dry air is 0.24 Btu per lb.
    Energy is required to produce desired
    temperatures for heating or cooling.

81
Degree Days
19.6.1
  • Measure used to indicate heating or cooling
    needed for a given region.
  • Calculation is based on a temperature of 65ºF
    (18ºC).
  • If degree-days are below this temperature, they
    are heating degree days.
  • If degree-days are above 65ºF (18ºC), they are
    cooling degree days.
  • Formula

82
Sun Heat Load Fundamentals
19.6.1
  • Radiant heat from the sun produces a large amount
    of heat energy.
  • Glass is a poor conductor of heat. Heat that
    enters as a light ray is trapped in a room as
    heat energy.
  • The suns rays heat the surfaces of buildings
    exposed to sunlight. Many building materials are
    poor conductors of heat. This heat source must be
    considered when designing heating and cooling
    requirements.

83
Sun Heat Load Fundamentals continued
19.6.1
  • Color has a considerable effect on amount of heat
    absorbed from the suns rays. Black and red
    absorb much more heat than white and yellow.
  • Surfaces that radiate heat are more efficient if
    painted dark colors.
  • Light-reflecting surfacespolished metal, chrome,
    etc.do not absorb heat easily. They do not
    radiate heat efficiently from their surfaces.

84
Wind
19.6.2
  • The Beaufort scale is used by the United States
    Weather Bureau to indicate wind velocity. It
    gives wind velocity values and effects.
  • An increase in wind velocity increases the heat
    loss of a heated structure.
  • Calculated heat load for a structure should
    include maximum wind velocity expected for the
    area.

85
Wind
19.6.2
86
Wind continued
19.6.2
  • During the winter months, the wind chill index
    combines temperature and wind speed.

87
Wind
19.6.2
88
Heat Insulation
19.7
  • In extremely hot or cold climates, building
    materials that do not transfer heat readily are
    desirable.
  • Insulation such as mineral wool, expanded mica,
    balsam wool, urethane may be used.

89
Heat Sink
19.7.1
  • When a warm body radiates heat rays, there are
    two common effects
  • Heat rays strike another surface of the same
    temperature and reflect back. There is no
    increase or decrease in heat in the body struck
    by the radiation.
  • If radiant heat strikes a surface that is colder
    than the radiating body, heat rays do not all
    bounce back. Some radiant heat is absorbed by the
    colder surface. The surface becomes a heat sink.

90
Stratification
19.7.2
  • If there is no air movement in a room, air will
    tend to stratify. Cold air will sink to the floor
    and warmer air will rise to the ceiling. Air
    movement in the room can prevent this.
  • If the thermostat is located in the upper part of
    a room with no air movement, the temperature
    difference will be more noticeable.

91
Four Types of Heat Exchange continued
19.7.3
  • Principles of heat exchange are used to create
    comfortable living environments. The tendency is
    to supply large surfaces at moderate
    temperatures. The large, warmed surfaces do not
    absorb body heat therefore, the occupant feels
    comfortable.
  • Four types of heat exchange
  • Radiation.
  • Convection.
  • Evaporation.
  • Conduction.

92
Four Types of Heat Exchange
19.7.3
  • Radiation.
  • A body of radiating heat. If the heat being
    radiated strikes a body or substance at a lower
    temperature, heat is lost to the
    lower-temperature substance. If a body is
    surrounded by surfaces at a higher temperature,
    the temperature of the body will increase.

93
Four Types of Heat Exchange continued
19.7.3
  • Convection.
  • The transfer of heat from one body to another
    through a medium, usually air or water.
    Conventional ovens heat by convection.

94
Four Types of Heat Exchange continued
19.7.3
  • Evaporation.
  • Evaporative heat exchange takes place from the
    human body. Moisture is fed to skin from sweat
    glands. Evaporation of this moisture lowers the
    skin temperature and constitutes a considerable
    heat exchange from the body.

95
Four Types of Heat Exchange continued
19.7.3
  • Conduction.
  • The transfer of heat between molecules or bodies
    in direct contact with one another.

96
Questions
23
  • Approximately _______ of the earths atmosphere
    is made up of oxygen.

3/4
  • About _____ of the earths atmosphere consists of
    nitrogen.

0.03
0.04
  • Approximately _____ to _____ of the atmosphere
    is made of carbon and oxygen.

methane
  • Hydrogen is present in fuels such as __________,
    ___________, and __________.

propane
butane
  • Rare gases make up from _______ to ______ of
    the atmosphere by weight.

0.9
1.3
97
Questions continued
neon
argon
  • Example of rare gases are ________, ________, and
    ________.

helium
Moisture
  • ___________ is always present in air.
  • The amount of moisture air can hold depends on
    ___________.

temperature
  • Warm air holds __________ moisture than cold air.

more
  • ______________ is the term used to express the
    amount of moisture in a given sample of air.

Relative humidity
98
Questions continued
low relative humidity
  • Excessive static electricity indicates
    __________________.
  • Which meter is used to measure relative humidity?

A hygrometer.
  • Name two commonly used desiccants.

Activated alumina and silica gel.
  • Which instrument is used to measure the wet bulb
    temperature of the air?

A sling psychrometer.
99
Questions continued
  • Which type of graph is used when working with air
    properties?

A psychrometric chart.
  • Name four variables measured by a psychrometric
    chart.

Dry bulb temperature, wet bulb temperature,
relative humidity, and dew point temperature.
  • Humans are comfortable in a relative humidity
    range between _____ and ____ at 70ºF to 85ºF
    (21ºC to 29ºC).

30
70
100
Questions continued
  • What is known as the temperature at which
    moisture in the air begins to condense?

The dewpoint temperature.
  • Name two instruments that measure air velocity.

An anemometer and a velocimeter.
  • Which two readings can be measured with a pitot
    tube and a manometer?

Velocity pressure and static pressure.
  • Name four types of heat exchange.

Radiation, convection, conduction, and
evaporation.
101
Chapter 19
AIR QUALITY MODULE
102
Air Quality
19.8
  • Affected by temperature, humidity, airflow,
    occupancy, and building materials.
  • Deterioration occurs by evaporation of liquids,
    presence of food, smoke, and high concentrations
    of certain gases.
  • National Institution for Occupational Safety and
    Health (NIOSH) developed specific criteria and
    exposure limits.
  • Occupational Safety and Health Administration
    (OSHA) set Permissible Exposure Limits (PEL)
    based on exposures in industrial settings.

103
Outdoor Air Contaminants
19.8.1
  • Three general classes of contaminants
  • Solids.
  • Liquids.
  • Gases and vapors.
  • Solids are kept in suspension in the air by air
    currents.

104
Outdoor Air Contaminants continued
19.8.1
  • Classifications of solid contaminants
  • Dust Results from wind, sudden disturbance of
    the earth, or mechanical work on a solid. Can
    originate from animal, vegetable, or mineral.
    Dust particles usually over 600 microns in size
    (0.024" in diameter).
  • Fumes Solids formed by condensation and
    solidification of materials that are ordinarily a
    solid, but have been put into a gaseous state
    usually by industrial or chemical processes.
    Particles are about 1 micron in size.

105
Outdoor Air Contaminants
19.8.1
106
Outdoor Air Contaminants continued
19.8.1
  • Classifications of solid contaminants
    (continued)
  • Smoke Produced by incomplete combustion. Solid
    particles carried into atmosphere by gaseous
    products of combustion. Particles vary in size
    from .1 to 13 microns.
  • Pollen grains from vegetation growth such as
    weeds, grasses, and trees. May cause hay fever,
    rose fever, and other respiratory conditions. Air
    conditioning should be capable of removing pollen
    from the air. Particles vary in size from 10 to
    50 microns.

107
Outdoor Air Contaminants continued
19.8.1
  • Classifications of solid contaminants
    (continued)
  • Bacteria Microorganisms responsible for the
    transmittal of many diseases. Manufacturing
    processes may require removal of bacteria.
    Hospital rooms and some refrigerators use
    bacteria-removing devices.
  • Mold Growth of minute fungi forming on vegetable
    and animal matter and on other surfaces. Many
    typical air conditioning applications provide an
    environment for their growth and development,
    especially if moisture is present. Spores from
    these molds can cause illnesses.

108
Outdoor Air Contaminants continued
19.8.1
  • Contaminants may be liquid in nature
  • Mists Small liquid particles mechanically
    ejected into air by splashing, mixing, atomizing,
    etc.
  • Fogs Small liquid particles formed by
    condensation suspended in the air. Fogs occur
    when atmosphere has reached saturation point.
    These particles may be contaminated with sulfur
    dioxide, fumes, smoke, and dust particles.

109
Outdoor Air Contaminants continued
19.8.1
  • Gases and vapors have condensing temperatures and
    pressures close to normal conditions.
  • Not all contaminants are objectionable or
    harmful. Perfumes and deodorizers make air more
    pleasant to breathe and can conceal objectionable
    odors.

110
Pollutants
19.8.1
  • The Clean Air Act of 1963 gives the United States
    Department of Health, Education, and Welfare the
    power to establish and enforce standards for
    clean air.
  • The pollutants named above as well as
    particulates, carbon monoxide, photochemical
    oxidants, and nitrogen oxides are included.
  • Photochemical oxidants result from the effect of
    sunlight on hydrocarbons and nitrogen oxides. The
    reaction produces smog.

111
Pollutants continued
19.8.1
  • Terpene, a hydrocarbon released from growing
    trees, may be considered a pollutant.
  • Methane is produced during the decomposition of
    vegetable matter.
  • Particulates include fogs, mists, molds, pollen,
    dust, fly ash, asbestos, and large bacteria.
  • Bacteria, viruses, and fungi are also found in
    the environment.
  • Construction and operation of air conditioning
    equipment may increase pollutants.

112
Pollutants continued
19.8.1
  • Sulfur dioxide is a common gaseous pollutant
    produced by burning coal, gas, or oil.
  • Hydrogen sulfide results from some industrial
    processes, especially papermaking.
  • Chlorine, paints, insecticides, and volatile
    solvents release polluting vapors.
  • Vapor-related illnesses are difficult to
    identify. However, when a patient is removed from
    the environment, symptoms should disappear.

113
Carbon Monoxide
19.8.1
  • Carbon monoxide is the result of incomplete
    combustion of fuel often in an automobile's
    exhaust. Fuel-burning furnaces also produce
    carbon monoxide. It is present in the combustion
    chamber, heat exchanger, flue, and stack.
  • An odorless, tasteless, and colorless gas, it
    produces headaches, nausea, and vomiting. If
    exposure is intense, a person may become
    unconscious and die.
  • Carbon monoxide replaces oxygen in red blood
    cells.

114
Various Pollutants
19.8.1
  • Nitrogen oxide is formed at high temperatures,
    including within an automobile engine. Nitrogen
    oxide is unstable. It produces smog.
  • Organic vapors are a major source of air
    pollution.

115
Various Pollutants continued
19.8.1
  • Portable odor monitor.
  • Digital display indicates odor concentration
    level.
  • Uses a highly sensitive metal oxide thermal
    conductivity sensor.

116
Ozone
19.8.1
  • A form of oxygen produced in nature by a
    photochemical process.
  • Created in the upper atmosphere by ultraviolet
    light reacting with oxygen.
  • May also be produced by lightening.
  • A disinfectant may be used to purify water or
    maintain a sterile atmosphere.
  • Used to remove odors from cold storage rooms and
    hospitals.

117
Ozone continued
19.8.1
  • No universal agreement exists concerning the
    benefits or hazards of using ozone in conditioned
    spaces. A small amount in the air is considered
    beneficial. Large concentrations may be harmful.
  • Ozone concentration of 0.1 parts per million
    (ppm) is considered the maximum permissible
    eight-hour exposure. For continuous occupancy,
    ozone should not exceed 0.01 ppm. The effect
    doubles for each 15ºF (8ºC) increase in
    temperature.
  • The use of some electronic air cleaners may
    slightly increase the ozone content.

118
Ozone continued
19.8.1
  • This ozone monitor indicates the ozone content of
    the area in 0 to 9.99 parts per million (ppm).

119
Pollen
19.8.1
  • Pollen Created by plants during certain seasons.
    Certain concentrations of pollen in the
    atmosphere may be irritating to many people. The
    most troublesome plants are ragweed, timothy,
    goldenrod, and roses.
  • Pollen count Determined by exposing an
    adhesive-coated surface to the atmosphere for 24
    hours. The number of pollen grains in a square
    centimeter determines pollen count for the past
    24 hours.

120
Indoor Air Quality (IAQ)
19.8.2
  • Concern due to improved building standards,
    including increased insulation and reduced
    energy-consuming ventilation systems.

121
Indoor Air Quality (IAQ) continued
19.8.2
  • Productivity can be increased 15 by improving
    the working environment.
  • IAQ problems are commonly classified as one of
    the following
  • Sick Building Syndrome (SBS).
  • Building Related Illness (BRI).
  • Multiple Chemical Sensitivity (MCS).
  • The majority of IAQ concerns stem from poor
    ventilation, poor filtration, and contaminated
    HVAC systems.

122
Sick Building Syndrome (SBS)
19.8.2
  • Occurs when approximately 20 of a buildings
    occupants complain of drowsiness, fatigue, eye
    and skin irritations, or respiratory problems.
  • Symptoms frequently disappear when an individual
    is removed from the environment.
  • OSHA defines SBS as a reaction to chemical,
    physical, or biological stimuli.

123
Sick Building Syndrome (SBS) continued
19.8.2
  • SBS results from the presence of any combination
    of
  • Poor temperature/humidity control.
  • Poor ventilation and lighting.
  • Improper maintenance and system design.
  • Airborne chemicals or pollutants.
  • Excess noise.

124
Building Related Illness (BRI)
19.8.2
  • Due to exposure to airborne agents.
  • Problems do not disappear when occupant moves to
    a more favorable environment.
  • Examples of BRI include Legionnaires disease,
    colds, flu viruses, tuberculosis, measles, and
    small pox.
  • Illnesses caused by BRI may cause permanent
    health problems and may be fatal.

125
Building Related Illness (BRI) continued
19.8.2
  • Causes of BRI
  • Viruses that are spread by the airflow in a
    system.
  • Stagnant water.
  • Toxins and allergens.
  • Radon.
  • Airborne biological agents (spores, fungi).

126
Multiple ChemicalSensitivity (MCS)
19.8.2
  • Experienced by a very small portion of the
    population.
  • Individuals appear to have abnormal sensitivity
    to chemicals in an environment.

127
Indoor Air Contaminants
19.8.3
  • Three major indoor air contaminants
  • Asbestos.
  • Bioaerosols.
  • Radon.

128
Asbestos
19.8.3
  • Silicate minerals that can separate into fibers.
  • Known for its strength and fire resistance.
  • Often used in old commercial buildings.
  • A known cancer-causing agent.
  • Exposure to asbestos generally occurs in four
    settings
  • Asbestos production (mining).
  • Materials production (insulation, brake linings).
  • Construction.
  • Removal.

129
Asbestos continued
19.8.3
  • Asbestos that has not deteriorated should be left
    alone.
  • Professional asbestos abatement companies must do
    asbestos removal.
  • Sampling or testing for asbestos is accomplished
    by environmental monitoring, including visual
    assessment and sampling.

130
Bioaerosols
19.8.3
  • Airborne microorganisms derived from viruses,
    bacteria, fungi, protozoa, mites, and pollen.
  • Found indoors and outdoors.
  • Excessive moisture indoors increases growth.
  • Humidifiers, water spray systems, and wet porous
    surfaces act as breeding grounds.
  • Microorganisms in the indoor environment may
    cause allergic building-related illness (BRI).

131
Bioaerosols continued
19.8.3
  • Inadequate preventative maintenance on the system
    provides the nutrients needed for the growth of
    bacteria such as Legionella. Proper maintenance
    of system may reduce this risk.
  • HVAC system should be checked when medical
    evidence indicates presence of diseases
    (humidifier fever, allergic asthma, etc.). An
    initial walkthrough inspection should occur
    looking for possible reservoirs and sites of
    contamination. If a site is located, a sample
    should be obtained and analyzed.

132
Radon
19.8.3
  • Odorless, tasteless, radioactive gas.
  • Occurs naturally in soil and rocks.
  • Formed by the natural decay of uranium and found
    in some industrial wastes.
  • Enters a building through small cracks in
    concrete floors, floor drains, sump pumps, and
    pores in hollow block walls.

133
Radon continued
19.8.3
  • Has been shown to cause lung cancer. When
    inhaled, it settles in the lungs. Radioactive
    particles damage lung tissue.
  • Detected using charcoal sent to a laboratory for
    analysis. If results confirm the presence of
    radon, entry points of gas must be located and
    repaired.

134
Carbon Dioxide (CO2)
19.8.3
  • Inhaled and exhaled by humans. Concentration of
    CO2 in exhaled breath is about 3.8. Once CO2
    leaves the mouth, it mixes with surrounding air.
  • When people exhale CO2, other gases, odors,
    bacteria and viruses are also exhaled.
  • If these gases build up in a space due to
    improper ventilation, poor air quality results.
    Symptoms include fatigue, headaches, and general
    discomfort. High CO2 concentrations indicate that
    the other contaminants may also be present.

135
Diagnosing IndoorAir Contamination
19.8.3
  • When evaluating ventilation, ASHRAE Standard
    62-1989 should be used.

Four Step Method for Evaluation of IAQ Building
Problem
136
Diagnosing IndoorAir Contamination continued
19.8.3
  • Procedure
  • Obtain a description of the symptoms from the
    occupants. Areas of concern are physical
    symptoms, odors, and the frequency and time of
    occurrence.
  • Determine possible sources. Examine the
    ventilation system and review any potential
    sources of contaminants. If a source is not
    evident, continue to the next step.
  • Take an air pollutant sample and perform a
    chemical analysis. Sampling should be done at an
    indoor location and an outdoor location near the
    system's air inlet.

137
Diagnosing IndoorAir Contamination continued
19.8.3
  • Procedure (continued)
  • Building-related contaminants peak in the morning
    after a system has been inactive throughout the
    night. Occupant-related contaminants peak in late
    afternoon. Interpret the data.
  • Implement proper procedures to correct the
    problem. Possible solutions include increasing
    ventilation, air cleaning, and controlling of
    problem areas.

138
Servicing Ventilation Systems
19.8.3
  • There are a variety of methods for measuring the
    required indoor air circulation.
  • This portable indoor environment monitor measures
    carbon dioxide levels and determines the proper
    ventilation for the area.

139
Servicing Ventilation Systems continued
19.8.3
  • Complete IAQ evaluators (demand control
    ventilation) are permanently installed in the
    ducts of large buildings.

140
Servicing Ventilation Systems continued
19.8.3
  • This is a wall-mounted carbon dioxide controller
    with digital CO2 indicator. Readings are
    transferred to a central system.

141
Servicing Ventilation Systems continued
19.8.3
  • This indoor air evaluator assesses ventilation
    quality by detecting, measuring, and recording
    carbon dioxide, temperature, and relative
    humidity.

142
Three Methods forMeasuring Filter Efficiencies
19.8.3
  • Atmospheric dust spot efficiency A measure of
    the filters ability to remove atmospheric dust.
  • Measures flow rates on both sides of a filter
    using two paper targets.
  • Efficiency is calculated based on the quantity of
    air drawn through the target filter, the amount
    of light transmitted through the target filter,
    and the difference in light transmission for the
    two paper targets.

143
Three Methods forMeasuring Filter Efficiencies
continued
19.8.3
  • Synthetic dust weight arrestance A measure of a
    filters ability to remove synthetic dust from
    test air.
  • Calculated are based on the weight of synthetic
    dust that passes through filter.
  • The end weight is compared to the weight of the
    amount fed into the filter.

144
Three Methods forMeasuring Filter Efficiencies
continued
19.8.3
  • DOP smoke penetration method Used mainly with
    high efficiency filters.
  • Particles of 0.3 microns are sprayed into the
    inlet duct of the filter.
  • Small, white sample filters collect some of the
    dust from the air stream ahead of the filter.
  • Other sample filters collect dust from the air
    leaving the filter.
  • The difference in sampling filters, by color or
    weight, determines the filter efficiency.

145
Duct Cleaning
19.8.3
  • Three-step process
  • Duct sweeper is rotated along the side of the
    ducts releasing dust, mold, and mildew.
  • A high-velocity commercial vacuum removes loose
    particles from the ductwork.

146
Duct Cleaning continued
19.8.3
  • Three-step process (continued)
  • Microbial biocide is sprayed into the cleaned
    duct system to help prevent mold and mildew
    buildup.
  • Filters should be checked, cleaned, or replaced
    if necessary.

147
Residential Air Quality Systems
19.9
  • A complete indoor air quality system includes an
    air conditioner, furnace, humidifier, electronic
    air-filter, and energy recovery vent heater.

148
Residential Air Quality Systems continued
19.9
  • Unit is a controlled ventilation system.
  • Reduces pollen, dust, odors, and other
    pollutants.
  • Unit exhausts stale humid air.
  • About 70 of existing heated air is used for
    recirculation.
  • Additional components and alarm systems may be
    added.

149
Commercial IndoorAir Quality Systems
19.9
  • Commercial systems ensure delivery of the correct
    amount of outdoor air.
  • Control space humidity and building pressure.
  • Improve building efficiency, indoor air quality,
    and increase comfort.

150
Thermometers
19.9.1
  • Electric thermometers are either battery or
    120VAC powered.

151
Thermometers continued
19.9.1
  • Probe reacts quickly and accurately.
  • Scale is calibrated in both Fahrenheit and
    Celsius degrees.
  • A recording thermometer helps locate malfunctions
    by creating 24 hour or 7 day temperature records.

152
Thermometers continued
19.9.1
  • A wet globe thermometer is designed to measure
    the overall comfort conditions in hot workplaces.
  • A hollow copper sphere is painted black and
    covered with double layer of black cloth.
  • A 5" aluminum tube is connected to the sphere.
    The tube is filled with water and capped at other
    end.
  • A dial thermometer stem passes through centerline
    of the tube and into the globe.
  • After a few minutes, the dial reading will
    indicate the wet globe temperature.

153
Manometers
19.9.2
  • This is a manometer with a pitot tube used for
    measuring the air velocity in ductwork.
  • Determines both total pressure and static
    pressure.
  • This is then used to determine velocity pressure.

154
Manometers continued
19.9.2
  • This is the method of connecting a manometer to
    the air duct to determine its pressure.
  • Pressure is usually measured in inches.
  • Sudden pressure changes must be avoided or liquid
    may be forced out of the manometer.

155
Manometers continued
19.9.2
  • Manometer scales are based on the following data
  • 14.7 psi 29.92" Hg 34' water
  • 1" Hg .491 psi
  • 1 psi 2.035" Hg
  • 1 psi 2.31' water
  • 1' water .432 psi
  • 1" water .036 psi

156
Manometers continued
19.9.2
  • A dial-type manometer may be used.
  • Two probes allow for a comparison of readings.

157
Barometers
19.9.3
  • Used to measure atmospheric pressure.
  • Used in air conditioning to measure pressure by
    the deflection of a bellows or diaphragm.
  • This is a recording barometer with selectable
    rotation period of 1 day, 7 days, or 31 days.

158
Comfort Conditions
19.10
  • Result of desirable combination of temperature,
    humidity, air movement, and air cleanliness.
  • Indoor comfort chart. Most people are comfortable
    at temperature and relative humidity indicated in
    center.

159
Comfort Conditions continued
19.10
  • Graph of a comfort zone.
  • Note dry-bulb and wet-bulb temperature lines, and
    relative humidity line.

160
Comfort Conditions continued
19.10
  • The effective temperature is the combined effect
    of dry bulb temperature, wet bulb temperature,
    and air movement provides an equal sensation of
    warmth or cold.
  • In summer, air conditioned buildings are usually
    kept at temperatures approximately 10ºF to 15ºF
    below the outside air temperature.

161
Comfort Conditions continued
19.10
  • Comfort range for most people in winter is
    between 66ºF (19ºC) dry bulb at 70 RH to 80ºF
    (27ºC) dry bulb at 20 RH.
  • The average person is most comfortable if the
    skin surface temperature is 91ºF (33ºC). This is
    maintained in winter by clothing and in summer by
    sweating.
  • Temperature related illnesses are called thermal
    disorders. In cold climates, a person's body
    temperature may drop few degrees below normal due
    to lower metabolism.
  • High temperatures may cause illness.
  • OSHA is investigating heat stress.

162
Comfort-Health Index (CHI)
19.10.1
  • ASHRAE recognizes a Comfort-Health Index (CHI).
  • The CHI indicates sensory, physiological, and
    health responses to prolonged exposures to
    extreme temperatures.
  • The chart shows that at comfortable temperatures,
    there is no sensation of warmth or cold and no
    physiological effects.
  • Moving down in temperature, the body is
    uncomfortable. Physiologically, the body attempts
    to correct the condition by shivering.

163
Comfort-Health Index (CHI)
19.10.1
164
Noise
19.11
  • Unwanted sound.
  • Often complaints of noise are due to air
    conditioning.
  • Noise problems are divided into three categories
  • Noise source.
  • Noise carrier.
  • Noise amplification.
  • Noise may be caused by vibration of an object or
    against another object.

165
Noise continued
19.11
  • Noise may be caused by high-speed air traveling
    through the ducts. This is often due to an
    undersized unit or duct.
  • Soft fabrics, such as drapes and fabric-covered
    furniture, are noise absorbers.
  • Felt-lined ducts or soft-insulation-lined ducts
    absorb noise.
  • Communities may have codes regulating how noisy a
    mechanism may be (decibel level limit).
  • If noise is a factor, velocity should be kept at
    minimum. An acoustical discharge chamber may be
    used. Ducts may be lined or wrapped with
    sound-absorbing material.

166
Noise Measurement
19.11.1
  • Sound waves are rapid changes of air pressure.
  • Sound strength and sound pressure level (SPL) are
    rated in decibels (dB).
  • Sound strength is the total amount of sound, in
    decibels, coming from unit.
  • Sound pressure is the strength, in decibels, of
    sound after traveling a specified distance from a
    source.
  • The international unit for sound frequencies is
    hertz (Hz), which is cycles per second (cps).

167
Noise Measurement continued
19.11.1
  • Sound pressure measured in pascals (Pa).

168
Noise Measurement continued
19.11.1
  • An increasing sound frequency tends to increase
    the apparent loudness, as the human ear does not
    respond equally to all frequencies. For most
    people, sounds in 1000 Hz to 4000 Hz range are
    easiest to hear.

169
Noise Measurement continued
19.11.1
  • Measurement of loudness of sound meters read in
    dB (A) or dBA.
  • The dBA scale loudness means a standard A filter
    is placed in the microphone circuit. Filter
    reduces the intensity of low frequencies.

170
Noise Measurement continued
19.11.1
  • Comparison of loudness measurements using dB and
    dBA scales shows filters effect.
  • Law regarding sound or noise level usually
    written around the A scale.

171
Noise Measurement continued
19.11.1
  • The Walsh-Healy Act limits the time that workers
    may be exposed to various sound levels.

172
Noise Measurement continued
19.11.1
  • A noise dosimeter may be used to measure sound
    levels. Based on OSHA standards, the instrument
    measures continuous, intermittent, and impulse
    noises in a range from80 dBA to 130 dBA.

173
Noise Measurement con
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