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Term 1: Thermodynamics > Thermodynamic powerpoint notes 1104 > Flashcards

Thermodynamic powerpoint notes 1104 Flashcards

1
Q

What is Refrigeration?

A

The transfer of heat from a place it is not wanted to a place where it is unobjectionable

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2
Q

Refrigeration is used to move heat around and maintain ________ and _____ _______

A

Temperature and Relative humidity

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3
Q

What is the key requirement to keeping a refrigeration system functional?

A

Cold liquid refrigerant must be continually flowing around object(s) that must be cooled

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4
Q

What are two applications of air conditioning?

A
  1. Comfort cooling (human comfort)

2. Process cooling (cooling for machines)

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5
Q

Upon arriving at a service call always ask first these two things?

A
  1. what is being kept cold

2. how cold

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6
Q

what is a compressor?

A

vapour pump (not meant to handle a lot of liquid)

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7
Q

what is an evaporator?

A

a heat transfer device that absorbs heat from the load (heat exchanger)

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8
Q

What is a condenser?

A

a heat transfer device that rejects heat from system (heat exchanger)

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9
Q

What is a metering device?

A

flow control device

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10
Q

What does BTU stand for?

A

British Thermal Unit

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11
Q

Conduction vs Convection?

A

Conduction is where heat travels from one molecule to molecule within a substance through physical contact and Convection is where heat travels through a fluid from one substance to another

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12
Q

Fluid can be ____ or ______ but not ______

A

liquid or vapour but not solid

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13
Q

Forced convection uses _____ or _____ to move fluids

A

fans or pumps

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14
Q

What is sensible heat?

A

heat transfer that results in a change in temperature of a substance?

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15
Q

What is latent heat?

A

heat transfer that results in a change of state of a substance with no change in temp.

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16
Q

Can latent heat be measured with a thermometer?

A

No because temp does not change

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17
Q

What is specific heat?

A

The number of BTU’s required to raise the temperature of 1Lb of substance 1 degree Fahrenheit

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18
Q

What is the specific heats of the following:

a) water
b) ice
c) steam
d) air

A

a) water is 1.00btu/lb
b) ice is 0.50btu/lb
c) steam is 0.50btu/lb
d) air is aproxx 0.24btu/lb

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19
Q

What are three forms of energy?

A

Thermal, Electrical, Mechanical

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20
Q

List three examples of thermal conductors:

A

Gold, Silver, Copper

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21
Q

List three examples of thermal insulators:

A

Foam, Fiberglass, Cork

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22
Q

What is the U-factor?

A

Overall coefficient of heat transfer

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23
Q

What is the K-factor?

A

thermal conductivity rating - pre inch thickness

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24
Q

What is the C-factor?

A

thermal conductance rating - given thickness

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25
Q

What is the R-factor?

A

thermal resistance -reciprocal of the U-factor

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26
Q

Heat cannot be ______ or _______

A

created or destroyed

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27
Q

What is the first law of thermodynamics?

A

Energy cannot be created or destroyed and all forms of energy are mutual convertible

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28
Q

What is the second law of thermodynamics?

A

Heat will always flow from a warmer area to a colder one

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29
Q

Water freezes at ____ degrees Fahrenheit and ____ degrees Celsius

A

32F

0C

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30
Q

Water boils at ___degrees Fahrenheit and ___ degrees celsius

A

212F

100C

31
Q

Molecular motion (Absolute zero) stops at ____ degrees Fahrenheit and ___ degrees Celsius

A
  • 460F

- 273C

32
Q

1W =_____BTU

A

3.413 BTU

33
Q

1KW=____BTU

A

3413 BTU

34
Q

1HP=___W

A

746W

35
Q

What is Enthalpy?

A

The total heat content (Qs + QL)

36
Q

Celsius to Fahrenheit formula?

A

F= (9/5) (C+32)

37
Q

Fahrenheit to Celsius formula?

A

C= (5/9) (F-32)

38
Q

Sensible heat formula?

A

Qs=Mass (lbs) x SpHt x changeT

39
Q

Latent heat formula?

A

QL=Mass (lbs) x Latent heat

40
Q

How much does 1 imperial gallon of water weigh?

A

10lbs

41
Q

How much does 1 US gallon of water weigh?

A

8.33lbs

42
Q

Specific heats of Milk?

A

Above 32 degrees Fahrenheit = 0.90 btu/lb

Below 32 degrees Fahrenheit = 0.46 btu/lb

43
Q

Freezing point of milk?

A

31 degrees Fahrenheit

44
Q

Explain Refrigeration ton?

A

It is based on the amount of heat required to melt one ton of ice in 24 hours?

45
Q

How many btu to melt 1 ton of ice in 24 hours?

A

288,000 btu/day

46
Q

What is saturation?

A

When a substance contains all of another substance it can gold for that temperature and pressure

47
Q

What is saturation pressure?

A

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

48
Q

What is saturated temperature?

A

The temp. at which a liquid turns into a vapour, or a vapour turns into a liquid

49
Q

When there is a mixture of liquid/vapour the substance is ______

A

saturated

50
Q

Boiling point is temperature change at ____ _____ and stays the same

A

sea level

51
Q

Saturated temp changes based on ___ _____. The _____ the pressure the ______ the boiling point becomes when it goes above sea level

A

sea level, lower, lower

52
Q

Higher pressure with a higher boiling point would be ____ _____ _____

A

below sea level

53
Q

What is saturated vapour?

A

Vapour that has all the heat it can hold without becoming superheated

54
Q

What is saturated liquid?

A

A liquid that has all the heat it can hold without changing into a vapour

55
Q

What is superheat?

A

The temperature of a vapour above its boiling point

56
Q

Superheat is always in _____ form

A

vapour

57
Q

What is superheat vapour?

A

A gas that has been heated to a temperature that is above its boiling point

58
Q

Why is superheat called a TD?

A

It is a temperature differential between vapour temperature and saturated temperature

59
Q

Three things required to find Superheat TD?

A
  1. Thermometer
  2. Gauge manifold
  3. PT chart
60
Q

What is gas?

A

A vapour that is superheated

61
Q

What is vapour?

A

A gas that is at its saturation temp and pressure

62
Q

What is sub cooled liquid?

A

A liquid at a temperature below its saturation temperature

63
Q

What is sub-cooling?

A

A temperature of a liquid that is below its boiling point

64
Q

Sub-cooling is a ____ and superheat is a ____

A

liquid, vapour

65
Q

Pascals law:

A

Pressure applied upon a confined space is transmitted equally in all directions

66
Q

Charles first law:

A

If the volume of a gas remains the same, then the absolute pressure varies directly with the absolute temp.

67
Q

Charles second law:

A

If the pressure of a gas remains constant, then the volume of the gas varies directly with the absolute temp.

68
Q

Boyles law:

A

If the temp remains constant, the volume of gas varies inversely to the absolute pressure

69
Q

The perfect law:

A

takes into account all the variables. If one of the variables constant then that variable can be dropped from the formula

70
Q

Perfect Law Formula?

A

P1xV1/T1 = P2xV2/T2

71
Q

Hg Vac perfect vacuum is ____ and atmosphere pressure is __

A

29.92 and 0

72
Q

What happens to refrigerant after it flows through the condenser?

A

it condenses to a liquid

73
Q

Name the 3 conditions of the refrigerant and give a brief description

A
  1. Temp: precise number/unit or just high/low temp
  2. Pressure: precise number/unit or just high/low press.
  3. State: Saturated liquid, Saturated vapour, sub-cooled, superheated vapour, saturated liquid/vapour mix

Term 1: Thermodynamics (8 decks)

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