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HVAR > Gas Works > Flashcards

Gas Works Flashcards

1
Q

Relationship between pressure and temperature.

A

For HVACR purposes, the crucial point at which pressure and temperature com together is point at which evaporation or condensation occurs, depending upon whether heat is being added or removed. The Heat/temperature char of water points out some important things about pressure and temperature.

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2
Q

Sub cooling

A

Liquid at the temperature blow its boiling point.

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3
Q

Super heat zone

A

Heat added to vapor above its saturated condition.

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4
Q

Latent heat

A

Heat added or taken away for 1 pound of a substance that causes a change in state, but not a change in temperature.

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5
Q

Heat of evaporation and condensation are _________ heat

A

Latent

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6
Q

Sub Cooling zone

A

Liquid at a temperature below its boiling point (sensible heat)

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7
Q

Super heat zone

A

Heat added to Vapor above its saturated condition.

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8
Q

Heat of freezing

A

Taking heat from water to get ice. (Latent heat)

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9
Q

Heat of melting

A

Adding heat to ice to get water. (Latent heat) 144 btu

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10
Q

Sensible heat

A

Heat added for removed from a substance that causes a change in temperature.

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11
Q

What happens to the boiling point of temperature if the pressure is increased?

A

Boiling point temperature go up.

Water is radiation in car boils a 250 degrees. Because it is held at 15 pounds of pressure.

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12
Q

Saturated Condition

A

Liquid and vapor in the same container under the same conditions

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13
Q

Inch Hq = micron= cm=mm

A

1.00 inch Hg = 25.400 microns=2.54cm=25.4mm
.100 inch Hg = 2,540 microns=.254cm=2.54mm
.039 inch hg = 1000 microns = .100cm=1.00mm

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14
Q

Micron

A

1 micron = 1 millionth of a meter.

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15
Q

Work

A

Force x distance

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16
Q

Power

A

Work x time

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17
Q

Boyle’s Law

A 
P up V down T =
P down V goes up T=
With a constant temperature
P = pressure
V = volume
T = temperature
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18
Q

Charles law

A

V up T up P =
V down T down P =
P up T up V=
P up T up V=

19
Q

Pascal law

A

Pressure on a fluid is transmitted equally in all directions.

Example: Brakes in your car

20
Q

Fluid

A

Is something the will flow. Liquid or a vapor or both.

21
Q

Critical pressure

A

Is a condition of fluids, including refrigerants at which liquid and gas have the same properties. This pressure is so high that the physical state of liquid and vapor merged

22
Q

Critical temperature

A

Is the highest temperature at which a gas can still be liquefied by the application of pressure. If vapor temperature is above the critical temperature, increasing pressure upon the vapor will not cause it to condense into liquid.

23
Q

Specific Gravity

A

Is the ratio of weight or mass of a given volume of a substance that of the same volume of a standard

With refrigerants the standard is air

Propane will sink. (It is heavier the air) Natural gas goes up (it is lighter than air)

24
Q

Saturated

A

A solution is said to be saturated when it can dissolve or contain no more of a substance and additional amounts will appear as precipitate. The point at which a change of state will occur

25
Q

Saturated condition

A

Term used to indicate the boiling or condensing point of a substance, which is dictated by a specific combination of temperature and pressure.

26
Q

Saturated liquid

A

A saturated liquid contains as much heat (thermal energy) as it can without boiling (changing state)

27
Q

Saturated vapor

A

Vapor at the same pressure and temperature as the liquid it contacts

28
Q

Vaoporization

A

The change of a liquid into a gaseous state

29
Q

Condensation

A

Liquid or droplets which form when a gas or vapor is cooled below its dew point

30
Q

Boiling point

A

The temperature at which a vapor pressure of liquid is equal to the surrounding atmospheric pressure so that liquid becomes a vapor, ie the temperature at which upward pressure of the molecules escaping from the surface equals the downward presume of the atmosphere.

31
Q

Change of state

A

The process that a substance (either a compound or element) goes through when changing from one physical state to another. Water to steam

32
Q

Vapor pressure

A

The pressure exerted by a saturated vapor above its own liquid in a closed container.

33
Q

Equilibrium

A

Conditions that exist a saturation or balance.

34
Q

Refrigerant

A

A substance used is a refrigeration system to absorb heat in the evaporator by changing liquid to gas and releasing this heat form the condenser when the substance returns to a liquid state.

35
Q

Saturated presure

A

The force in a pressure vessel that matches the temperature of certain contained gas at a condition where any removed heat would cause condensation, and added heat would cause evaporation

36
Q

Three names of the men for the gas laws

A

Robert Boyle
Jacques Charles
John Dalton

37
Q

Temperature

A

As a measurement of the intensity of heat present in a substance

38
Q

Absolute zero

A

Represents the complete absence of heat in a substance

  • 460 degrees below zero.
  • 273 Celsius
39
Q

Change Fahrenheit to Rankine

A

Add 460 is above zero

Subtract 460 if below zero

40
Q

Presure

A

As force per until area

Sea level 14.696

41
Q

Volume

A

Is space that a substance occupies or can occupy

42
Q

Pressure conversion

Convert barometric pressure to psia

A

Divid barometric pressure by 2.036

43
Q

Convert PSIA to HG

A

Multiply the psia by 2.036

44
Q

Calculate pressure at Constant Volume

Take a 1 ft cylinder of nitrogen at 70 degrees. A gauge on it he shows 700 psig. What will the gauge show if the cylinder temp is raise 90

A

70F +460=530 t1
90F + 460= 550 t2

700 psig + 14.7= 714.7 or p1

P2 is

550r by 714 psia then devid by 530 the answer is 741.7

HVAR (5 decks)

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