Thermodynamic powerpoint notes 1104

Question 1

What is Refrigeration?

Answer 1

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

Question 2

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

Answer 2

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

Question 3

What are two applications of air conditioning?

Answer 3

1. Comfort cooling (human comfort)

2. Process cooling (cooling for machines)

Question 4

Conduction vs Convection?

Answer 4

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

Question 5

Fluid can be ____ or ______ but not ______

Answer 5

liquid or vapour but not solid

Question 6

Forced convection uses _____ or _____ to move fluids

Answer 6

fans or pumps

Question 7

What is sensible heat?

Answer 7

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

Question 8

What is latent heat?

Answer 8

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

Question 9

Can latent heat be measured with a thermometer?

Answer 9

No because temp does not change

Question 10

What is specific heat?

Answer 10

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

Question 11

What is the specific heats of the following:

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

Answer 11

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

Question 12

What are three forms of energy?

Answer 12

Thermal, Electrical, Mechanical

Question 13

List three examples of thermal conductors:

Answer 13

Gold, Silver, Copper

Question 14

List three examples of thermal insulators:

Answer 14

Foam, Fiberglass, Cork

Question 15

What is the U-factor?

Answer 15

Overall coefficient of heat transfer

Question 16

What is the K-factor?

Answer 16

thermal conductivity rating - pre inch thickness

Question 17

What is the C-factor?

Answer 17

thermal conductance rating - given thickness

Question 18

What is the R-factor?

Answer 18

thermal resistance -reciprocal of the U-factor

Question 19

Heat cannot be ______ or _______

Answer 19

created or destroyed

Question 20

What is the first law of thermodynamics?

Answer 20

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

Question 21

What is the second law of thermodynamics?

Answer 21

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

Question 22

Water freezes at ____ degrees Fahrenheit and ____ degrees Celsius

Answer 22

32F

0C

Question 23

Water boils at ___degrees Fahrenheit and ___ degrees celsius

Answer 23

212F

100C

Question 24

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

Answer 24

• 460F

- 273C

Question 25

1W =_____BTU

Answer 25

3.413 BTU

Question 26

1KW=____BTU

Answer 26

3413 BTU

Question 27

1HP=___W

Answer 27

746W

Question 28

What is Enthalpy?

Answer 28

The total heat content (Qs + QL)

Question 29

Celsius to Fahrenheit formula?

Answer 29

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

Question 30

Fahrenheit to Celsius formula?

Answer 30

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

Question 31

Sensible heat formula?

Answer 31

Qs=Mass (lbs) x SpHt x changeT

Question 32

Latent heat formula?

Answer 32

QL=Mass (lbs) x Latent heat

Question 33

How much does 1 imperial gallon of water weigh?

Answer 33

10lbs

Question 34

How much does 1 US gallon of water weigh?

Answer 34

8.33lbs

Question 35

Specific heats of Milk?

Answer 35

Above 32 degrees Fahrenheit = 0.90 btu/lb | Below 32 degrees Fahrenheit = 0.46 btu/lb

Question 36

Freezing point of milk?

Answer 36

31 degrees Fahrenheit

Question 37

Explain Refrigeration ton?

Answer 37

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

Question 38

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

Answer 38

288,000 btu/day

Question 39

What is saturated temperature?

Answer 39

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

Question 40

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

Answer 40

saturated

Question 41

What is saturated vapour?

Answer 41

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

Question 42

What is saturated liquid?

Answer 42

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

Question 43

What is superheat?

Answer 43

The temperature of a vapour above its boiling point

Question 44

Superheat is always in _____ form

Answer 44

vapour

Question 45

What is superheat vapour?

Answer 45

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

Question 46

Why is superheat called a TD?

Answer 46

It is a temperature differential between vapour temperature and saturated temperature

Question 47

Three things required to find Superheat TD?

Answer 47

1. Thermometer 2. Gauge manifold 3. PT chart

Question 48

What is gas?

Answer 48

A vapour that is superheated

Question 49

What is vapour?

Answer 49

A gas that is at its saturation temp and pressure

Question 50

What is sub cooled liquid?

Answer 50

A liquid at a temperature below its saturation temperature

Question 51

What is sub-cooling?

Answer 51

A temperature of a liquid that is below its boiling point

Question 52

Sub-cooling is a ____ and superheat is a ____

Answer 52

liquid, vapour

Question 53

Pascals law:

Answer 53

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

Question 54

Charles first law:

Answer 54

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

Question 55

Charles second law:

Answer 55

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

Question 56

Boyles law:

Answer 56

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

Question 57

The perfect law:

Answer 57

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

Question 58

Hg Vac perfect vacuum is ____ and atmosphere pressure is __

Answer 58

29.92 and 0