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HVAC Quiz 1 > HVAC Quiz 1 > Flashcards

HVAC 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 gas 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 that 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

AIR HANDLING UNIT (AHU)

A

A central unit consisting of a blower, heating and/or cooling elements, filter racks, dampers, humidifier, 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. At sea level this pressure is 14.696 pounds per square inch.

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9
Q

BOILING POINT

A

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

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10
Q

BRITISH THERMAL UNIT (BTU)

A

The amount of heat necessary to change the temperature of 1 pound of pure water 1 degree Fahrenheit (oF).

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11
Q

CENTIGRADE

A

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

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12
Q

CONDENSING UNIT

A

Normally referred to as an air conditioner or heat pump, a condensing unit functions as a heat transfer point. The heated refrigerant returned from the evaporator coil (or air handler/fan coil) located 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 the heat which is dispelled into the outside air, thus cooling the refrigerant to then 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 molecule within a substance.

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14
Q

CONVECTION

A

The transfer of heat by a moving fluid.

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15
Q

COP

A

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

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16
Q

CUBIC FEET PER MINUTE

A

A common means of assigning quantitative values for a volumetric flow rate of air in transit, usually abbreviated CFM.

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17
Q

DENSITY

A

Mass or weight per unit of volume. For example, standard air = .075 pounds per cubic foot.

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18
Q

DEW POINT

A

The temperature of air at saturation, or the temperature to which the 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

These are the conduits or channels that carry air throughout a building.

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22
Q

ENTHALPY

A

Total heat energy in a substance. The sum of sensible and latent heat. (BTU’s per pound of dry air).

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23
Q

EQUIVALENT LENGTH

A

That length of straight tubing which has the same pressure drop as the fitting, valve or accessory (of the same nominal size) being considered.

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24
Q

EVAPORATOR COIL

A

The portion of a central air conditioning system that is located in the zone and connected to the fan/ductwork. It functions as the heat transfer point for cooling indoor air. An evaporator coil is comprised of a series of coils filled with refrigerant. As the warm/hot air from the 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

The sum of the static and velocity pressures of a moving air system at the point of measurement.

26
Q

FAHRENHEIT

A

A temperature scale with the freezing point of water 32 deg F and the boiling point 212 deg F at sea level.

27
Q

FEET PER MINUTE

A

A term assigned to a velocity of a moving air stream, usually express FPM.

28
Q

FENESTRATION

A

A term referring to windows and other exterior openings of a building.

29
Q

FREEZING POINT

A

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

30
Q

GAUGE PRESSURE

A

Pressure measured relative to atmospheric pressure.

31
Q

HEAT

A

A form of energy causing the agitation of molecules within a substance.

32
Q

HEAT EXCHANGER

A

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

33
Q

HEAT FLOW

A

Heat flows from a warmer to a cooler substance. The rate depends upon the temperature difference, the area exposed and the type of material.

34
Q

HEAT TRANSFER

A

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

35
Q

HUMIDITY RATIO

A

The mass of water vapor carried by a unit mass of dry air. (lb. of water per lb. of dry air)

36
Q

HVAC

A

An acronym for heating, ventilation, and air-conditioning system

37
Q

INCHES OF MERCURY

A

Atmospheric pressure is equal to 29.92 inches of mercury.

38
Q

MANOMETER

A

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

39
Q

MBH

A

One MBH is equivalent to 1,000 BTU’s per hour.

40
Q

MINIMUM OUTSIDE AIR

A

The lowest amount of fresh air flow that must be introduced into a re-circulating system. This limit is sent to ensure that the interior air remains safe and comfortable to breathe.

41
Q

NATRUAL VENTILATION

A

In HVAC 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 air stream 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

PSYCHROMETRIC CHART

A

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

44
Q

R-VALUE

A

A measure of the capacity of a material to resist heat transfer. The R-Value is the reciprocal of the conductivity of a material (U-Value). The larger the R-Value of a material, the greater it?s insulating properties.

45
Q

RADIATION

A

The transfer of heat without an intervening medium. It is absorbed on 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. Sensible heat always causes a temperature rise.

49
Q

SPECIFIC VOLUME

A

The reciprocal of density. It is volume of the air/water vapor mixture in a unit mass of dry air. (cu. ft. per 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 deg. F ice in 24 hours. (200 BTUs per minute or 12,000 BTUs per hour)

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. Vapor barriers are 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 is encased in a wetted wick.

HVAC Quiz 1 (1 decks)

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