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HVAC > Quiz 1 > Flashcards

Quiz 1 Flashcards

1
Q

Absolute Pressure

A

Pressure measured with a base of zero

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2
Q

Adiabatic

A

A change in condition where no heat is added or removed except in the form of work

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3
Q

Air changes per hour (ACH)

A

The number of times per hour that the volume of a specific room or building is supplied or removed from the space by mechanical ventilation

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4
Q

Air conditioning

A

The process of controlling the volume flow rate, quality, temperature, and/or humidity of the air

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5
Q

AHU

A

Air Handling Unit
A central unit consisting of a blower, heating/cooling elements, filter racks, and other central equipment in direct contact with the airflow

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6
Q

Ambient

A

Refers to the temperature surrounding a body or unit

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7
Q

ASHRAE

A

The American Society of Heating, Refrigerating, and Air conditioning Engineers

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8
Q

Atmospheric pressure

A

The weight of a 1 square inch column of the earth’s atmosphere
14.696 psi at sea level

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9
Q

Boiling point

A

The temperature at which the addition of any heat will begin a change state from a liquid to a vapor

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10
Q

BTU

A

British Thermal Unit

The amount of heat necessary to change the temperature of 1 pound of pure water 1 degree Fahrenheit

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11
Q

Centigrade

A

A temperature scale with the freezing point of water at 0 degrees and the boiling point at 100 degrees at sea level

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12
Q

Condensing Unit

A

Aka air conditioner or heat pump
Functions as a heat transfer point
Heated refrigerant returned from evaporator coil (or air handler/fan coil) inside the zone is sent outside to the air conditioner/heat pump where it is pressurized and sent through the condensing coil
Under high pressure, the refrigerant gives up heat which is dispelled into the outside air, cooling the refrigerant to be sent back inside to the evaporator coil or air handler to repeat the process

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13
Q

Conduction

A

The transfer of heat from molecule to molecules within a substance

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14
Q

Convention

A

The transfer of heat by a moving fluid

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15
Q

COP

A

Coefficient of Performance

Ratio of work performed or accomplished as compared to the energy used

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16
Q

CFM

A

Cubic feet per minute

A common means of assigning quantitative values for a volumetric flow rate of air in transit

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17
Q

Density

A

Mass or weight per unit of volume

Standard air=.75lb/ft3

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18
Q

Dew point

A

The temperature of air at saturation

The temperature to which air must be cooled for condensation to begin

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19
Q

Dry air

A

Air which contains no moisture vapor

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20
Q

Dry bulb temperature

A

Temperature read with an ordinary thermometer

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21
Q

Ductwork

A

Conduits or channels that carry air though a building

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22
Q

Enthalpy

A

Total heat energy in a substance
Sum of sensible and latent heat
BTUs per pound of dry air

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23
Q

Equivalent length

A

Length of straight tubing that has the same pressure drop as the fitting, valve, or accessory (off same nominal size) being considered

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24
Q

Evaporator coil

A

Portion of central air conditioning system located in zone and connected to fan/ductwork
Functions as heat transfer point for cooling indoor air
Comprised of series of coils filled with refrigerant
As warm air from zone is returned to the HVAC system it blows through the evaporator coil where the refrigerant filled tubes extract both heat and extra moisture, thus cooling the air

25
Q

External static pressure

A

Sum of static and velocity pressures of a moving air system at point of measurement

26
Q

Fahrenheit

A

Temperature scale with freezing point of water at 32 degrees and the boiling point at 212 degrees at sea level

27
Q

FPM

A

Feet per minute

Term assigned to a velocity of a moving air stream

28
Q

Fenestration

A

Term referring to windows and other exterior openings of a building

29
Q

Freezing point

A

Temperature at which the removal of any heat will begin a change of state from liquid to solid

30
Q

Gauge pressure

A

Pressure measured relative to atmospheric pressure

31
Q

Heat

A

Form of energy causing adoration of molecules in a substance

32
Q

Heat exchanger

A

A device for the transfer of heat energy from the source to the converting medium

33
Q

Heat flow

A

Heat flows from a warmer to cooler substance

Rate depends on temperature difference, area exposed, and type of material

34
Q

Heat transfer

A

The three methods of heat transfer are conduction, convection, and radiation

35
Q

Humidity ratio

A

Mass of water vapor carried by unit mass of dry air

Pounds of water per pound of dry air

36
Q

HVAC

A

Acronym for heating, ventilating, and air conditioning system

37
Q

Inches of mercury

A

Atmospheric pressure is equal to 29.92 inches of mercury

38
Q

Manometer

A

Water filled tube used to measure differential pressure, in inches of water

39
Q

MBH

A

1 MBH=1000 BTUh (BTUs per hour)

40
Q

Minimum outside air

A

Lowest amount of fresh air that must be introduced into a recirculating system
Limit is set to ensure that the interior air remains safe and comfortable to breathe

41
Q

Natural ventilation

A

The movement of outdoor air into a space through intentionally provided openings, such as windows and doors, or by infiltration

42
Q

Pitot tube

A

A device comprising a small diameter orifice projecting directly into an airstream measuring total pressure and surrounded by an annular section with small diameter entrances normal to the flow, measuring static pressure
Both sections are usually connected

43
Q

Psychometric chart

A

A chart on which can be found the thermodynamic properties of air-vapor mixture under varying conditions of temperature

44
Q

R-value

A

A measure of the capacity of a material to resist heat transfer
Reciprocal of the conductivity of a material (U-value)
The larger the R-value, the greater its insulating properties

45
Q

Radiation

A

The transfer of heat without an intervening medium

It is absorbed in contact with a solid surface

46
Q

Refrigerant

A

A substance which produces a cooling effect while expanding or vaporizing

47
Q

Relative humidity

A

The percentage of water vapor present in a given quantity air compared to the amount it can hold at its temperature

48
Q

Sensible heat

A

Heat that can be measured or felt

Always causes a temperature rise

49
Q

Specific volume

A

Reciprocal of density

Volume of air/water vapor mixture in a unit mass of dry air (ft3/lb of dry air)

50
Q

Static pressure

A

The normal force per unit area at a small hole in the wall of a duct

51
Q

Temperature

A

A measurement of heat intensity

52
Q

Thermostat

A

A bimetal actuated switch used to open and close a circuit to terminate or initiate the operation of a heating or air conditioning system

53
Q

Ton of refrigeration

A

The amount of heat necessary to completely melt one ton of 32 degree F ice in 24 hours

54
Q

Vacuum

A

Any pressure below atmospheric pressure

55
Q

Vapor barrier

A

The term applied to an impervious layer of material superimposed upon a layer of insulation
Always applied on the warm side of the insulation layer

56
Q

Vapor pressure

A

The pressure exerted by vapor

57
Q

Velocity pressure

A

In a moving fluid, the pressure capable of causing an equivalent velocity as applied to move the same fluid through an orifice such that all pressure energy expanded is converted into kinetic energy

58
Q

Wet bulb temperature

A

Temperature read with a thermometer whose bulb ended in a wetted wick

HVAC (1 decks)

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