Thermodynamics

Question 1

The state of matter is determined by what two things

Answer 1

Pressure and temperature

Question 2

What best describes heat

Answer 2

Molecular motion

Question 3

When matter is in a gaseous state. It has

Answer 3

No size or definite shape

Question 4

What are the units to measure heat

Answer 4

British thermal units (btu’s)

Question 5

What is the process where a substance changos directly from a solid to gaseous state without becoming a liquid?

Answer 5

Sublimation

Question 6

The zero state of enthalpy is: (water)

Answer 6

32 F

Question 7

Name the three physical states of matter.

Answer 7

Solid
Liquid
Gas

Question 8

Name the four stages of refrigeration cycle

Answer 8

Expansion
Evaporation
Condensation
Compression

Question 9

Name the three methods of heat transfer.

Answer 9

Conduction
convection
Radiation

Question 10

Name the two substances used to cool condensers.

Answer 10

Air
Water

Question 11

Name four common heat exchangers used in your plant: (excluding - condenser and evaporator),

Answer 11

a. TRANSFORMERS COOLING RADIATOR
b. COMPRESSOR Aftercooler/intercooler
C. SURFACE AIR COOLERS
d. OIL TUB COOLING COILS

Question 12

When heat is applied to any substance, the density of the substance will:
(Exception-water)

Answer 12

Decrease

Question 13

Water is an its densest point at approximalety:

Answer 13

39F

Question 14

The beat that causes a change of state without a temperature change is called

Answer 14

Latent heat

Question 15

The amount of heat in BTU’s required to increase the temperature of one pound of a particular substance one degree at ges level pressure is called:

Answer 15

Specific heat

Question 16

A Fluid that picks up heat by evaporating at a low temperature and pressure and gives up heat by condensing at a higher temperature and pressure is called a refrigerant compound.T/F

Answer 16

True

Question 17

Temperature is the measure of the intensity of heat T/F

Answer 17

True

Question 18

When a unit of heat is added to a substance and the temperature increases,
this ter is called specific heat T/F

Answer 18

False

Question 19

The theoretical temperature at which molecular motion stops is caved absolute motion T/F

Answer 19

False

Question 20

A refrigerant gives up heat when it evaporates T/F

Answer 20

False

Question 21

What takes place inside the evaporator of a refrigeration system?

Answer 21

B. Latent heat of vaporization

Question 22

The heat required to change the state of water to vapor is called:

Answer 22

D. Latent heat of vaporization

Question 23

There are two kinds of dry steam. What are they?

Answer 23

D. Saturated and superheated

Question 24

What takes place inside the condenser of a refrigeration system?

Answer 24

A. Latent heat of condensation

Question 25

Steam in its purest form is?

Answer 25

C. Invisible to the eye

Question 26

The temperature at which a refrigerant will change state from a liguid to a vapor or vice versa?

Answer 26

A. Saturation temperature

Question 27

The main purpose of a condenser is to

Answer 27

B. Remove heat from the refrigerant

Question 28

The ability of a substance to conduct heat, or the rate of conduction is called

Answer 28

D. Thermal conductivity

Question 29

Water vapor that is heated above its saturation point and is no longer in the presence of water is

Answer 29

D. Superheated steam

Question 30

When heat is added to water at atmospheric pressure what would happen to the molecules

Answer 30

C increase in speed

Question 31

if the temperature of air that flows through a heat exchanger decreases from high temperature to a lower temperature this is a(n);

Answer 31

A. Evaporator

Question 32

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

Answer 32

C. Refrigeration

Question 33

When a substance is at its critical point. the properties of:

Answer 33

B. Liquid and vapor are indistinguishable

Question 34

What component is not part of the high side in an AC system?

Answer 34

B. Evaporator

Question 35

How many BTU’s will it take to heat 10 pounds of lead at atmospheric pressure, from 22F to 350F? Specific heat of lead is .03)

Answer 35

Weight•specific heat•(t1-t2) = BTU 10•.03•(350-22)= 98.4

Question 36

When one pound of waler at 32F evaporates it will' remove about:

Answer 36

Sensible heat• latent heat of vaporization= 180+970= 1150BTU’s

Question 37

What is the specific heat of gold if a 5 pound bar requires 21 BTU's to rise is temperature from 95° F to 235• F at atmospheric pressure

Answer 37

Specific heat= weight•( T1-T2) 5•(235-95)=700 21/700= .03 is the answer

Question 38

Change 90° Fahrerhat to kelvin

Answer 38

F to C = 5/9(F-32) = 5/9(90-32)= 32C C to K =C+273 = 32+273= 305K Answer = 305K

Question 39

How many BTU’s are required to change 15 pounds of -10F ice to 300F steam at atmospheric pressure?

Answer 39

BTU=weight•specific heat•(t1-t2) 15•.5•(32+10)= 315 315+(15•144)+(15•180)+(15•970)+(15•.5•(300-212))= Answer= 20,385BTU’s

Question 40

Change 315° Kelvin to Fahrenheit.

Answer 40

K to C K-273 = 315-273 = 42 C to F 9/5C+32 = 9/5(42)+32 = 107.6F Answer= 107.6F

Question 41

How many BTU’s will it take to heat 20 pounds of water at atmospheric pressure, from 60F to 212F

Answer 41

BTU=weight•specific heat•(t1-t2)= 20•1•(212-60)= 3040 3040+(20•970)= 22440BTU’s= answer

Question 42

How many BTU's must be added to one pound of ice at 30° F. To change It to 32F water?

Answer 42

BTU=weight•specific heat•(t1-t2) 1•.5•(32-30)= 1 1+144= 145BTU’s= answer

Question 43

Explain what happens in the refrigeration cycle. Include components, their purpose within the system and the prosesses that take place within each

Answer 43

Explain