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HVAC and Refrigeration Systems Training Manual > Midterm > Flashcards

Midterm Flashcards

1
Q

The condition that occurs when a person cannot sense the difference between themselves and the surrounding air.

A

Comfort

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2
Q

The condition that occurs when a person can sense the difference between themselves and the surrounding air.

A

Discomfort

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3
Q

A method of heat transfer
caused by the direct physical contact of substances.

A

Conduction

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4
Q

A method of heat transfer
in which heat is moved from one location to another through the circulation of a substance.

A

Convection

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5
Q

A method of heat transfer in which invisible heat rays move heat.

A

Radiation

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6
Q

What are the two main causes of combustion inefficiency?

A

incomplete combustion and an excess amount of air

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7
Q

How many conditions must be known in order to complete a psychrometric chart?

A

2 of the 7

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8
Q

How is a vacuum measured?

A

In inches of mercury

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9
Q

Define Absolute pressure.

A

Any pressure above a perfect vacuum (0 psi).

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10
Q

Define a Vacuum.

A

Any pressure that is less than atmospheric pressure.

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11
Q

The force exerted by the weight of the atmosphere (gas molecules) on the earth’s surface.

A

Atmospheric pressure.

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12
Q

A pressure measurement above atmospheric pressure that is used to express pressure derived from the operation of a closed system.

A

Gauge pressure

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13
Q

The ability of a material
to hold heat.

A

Specific heat

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14
Q

The measurement of a liquid’s resistance to flow (thickness).

A

Viscosity

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15
Q

The process of breaking a liquid into small droplets.

A

Atomization

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16
Q

A chemical reaction in fuel that occurs when oxygen reacts with hydrogen (H) and carbon (C) at an ignition temperature.

A

Combustion

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17
Q

How are air conditioning systems cooling often measure in?

A

Tons

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18
Q

Define a British thermal unit (Btu)

A

The quantity of heat required to change the temperature of 1 lb of water 1°F.

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19
Q

Define a ton.

A

The amount of heat required to melt one ton of ice (2000 lbs) over 24 hr. One ton of cooling equals 12,000 Btu/hr or 288,000 Btu/24 hr (12,000 x 24 = 288,000).

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20
Q

Define Humidity

A

The amount of moisture, or water vapor, in air.

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21
Q

What determines the amount of ventilation necessary for comfort?

A

The number of occupants and the kind of activity taking place inside the building.

22
Q

The amount of work that can be performed by a force.

A

Energy

23
Q

What are the different forms of energy? (7)

A

Heat (thermal), gravity, sounds, light, chemical, electrical, and mechanical energy.

24
Q

What is occurring when an insufficient amount of oxygen is supplied by combustion air to combine with all the elements in a fuel?

A

Incomplete combustion

25
Q

The temperature of air if it was cooled to 100% relative humidity?

A

Wet-bulb temperature

26
Q

What is the energy of work?

A

Mechanical

27
Q

The heat applied to or removed from a substance that results in a temperature change?

A

Sensible heat

28
Q

The heat applied to or removed from a substance that results in a change of state.

A

Latent heat

29
Q

What are the oxygen, carbon dioxide, and carbon monoxide levels of a fuel used to determine?

A

Combustion efficiency

30
Q

Any substance that is burned to produce heat.

A

A fuel

31
Q

Fuel, oxygen, and ignition temperature are the three requirements of what process?

A

Combustion

32
Q

What two readings are used to adjust a burner so that it will operate as efficiently as possible?

A

Carbon dioxide and flue-gas temperature

33
Q

People tend to have the best comfort at a what relative humidity?

A

45%

34
Q

A graph that defines the properties of air at various conditions.

A

Psychrometric chart

35
Q

What temperature is the temperature at which water vapor in the air begins to condense?

A

Dewpoint

36
Q

The process of reducing air pollution by introducing enough fresh outdoor air into a building to dilute indoor pollutants.

A

Ventilation

37
Q

Building HVAC systems typically use what for heating and cooling?

A

Furnace or boilers for heating and air conditioners or chillers for cooling.

38
Q

What air velocity, in buildings, is considered ideal for comfort?

A

40 fpms

39
Q

A self-contained building cooling unit that has the components contained in one cabinet.

A

A packaged unit

40
Q

The amount of moisture in the air compared to the amount of moisture the air would hold at the same temperature when air is saturated, or full of moisture.

A

Relative humidity

41
Q

What device removes moisture from the air by causing the moisture to condense or be trapped?

A

A dehumidifier

42
Q

The rate at which work (in ft-lb) is produced per unit of time (in sec).

A

Power

43
Q

A colorless and odorless gas fuel.

A

Natural gas

44
Q

What takes place in a furnace or boiler to heat a building?

A

Combustion

45
Q

What type of combustion occurs when enough oxygen is supplied by combustion air to combine with all elements in a fuel?

A

Complete combustion

46
Q

What type of air is provided to a burner for the proper combustion of a fuel?

A

Combustion air

47
Q

The point at which a flame is established.

A

Burner face

48
Q

The temperature of air as taken with a standard thermometer.

A

Dry-bulb temperature

49
Q

The total amount of heat contained in a substance.

A

Enthalpy

50
Q

What is used to express enthalpy?

A

BTUs

51
Q

The carbon dioxide and other va-
pors that exit a furnace or boiler to the atmosphere using a flue, which is a pipe or channel for conveying exhaust
gases.

A

Flue gas

HVAC and Refrigeration Systems Training Manual (3 decks)

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