Thermodynamics

Question 1

What is saturated steam

Answer 1

Saturated steam is steam at a temperature corresponding to its pressure

Question 2

What is superheated steam

Answer 2

Superheated steam is steam at a temperature higher than the temperature corresponding to its pressure

Question 3

What is meant by the term “degree of superheat’’

Answer 3

The number of degrees higher than the saturation temperature corresponding to its pressure

Question 4

Steam exists in three (3) forms. What are they

Answer 4

Steam can be wet, dry or superheated

Question 5

What is sensible heat

Answer 5

Sensible heat is heat added to a substance that causes a change in temperature that can be measured with a thermometer

Question 6

What is latent heat

Answer 6

Latent heat is heat added to a substance that causes a change of state without a change in temperature

Question 7

What is the definition of a BTU

Answer 7

A British thermal unit is the amount of heat required to raise one pound of water 1℉

Question 8

What is the definition of specific heat

Answer 8

Specific heat is the heat required to raise one pound of any substance 1℉

Question 9

What is specific gravity

Answer 9

Specific gravity is the weight of any substance when compared to the weight of water. Also known as density

Question 10

How many BTU’s are required to change 1 pound of water at 212℉ to one pound of steam at 212℉

Answer 10

970.3 btu’s per pound are required to change one pound of water at 212℉ into one pound of steam at 212℉

Question 11

How many BTU’s are required to change 1 pound of ice at 32℉ into one pound of water at 32℉

Answer 11

144 btu’s

Question 12

How much does 10,000 gallons of water weigh

Answer 12

10,000 X 8.33 lbs/gallon = 83,300 lbs

Question 13

How many BTU’s are required to raise the temperature of 100 gallons of water from 50℉ to 150℉

Answer 13

100 gallons X 8.33 lbs/gallon = 833 lbs.

833 lbs X 100 btu’s per pound = 83,300 btu’s

Question 14

What are the 5 headings on the steam table

Answer 14

• absolute pressure
• absolute temperature
• specific volume
• enthalpy btu’s/lb
• entropy

Question 15

Describe saturated and superheated steam

Answer 15

Saturated is steam at a temperature corresponding to its temperature. Super-heated steam is steam above the temperature corresponding to its pressure and contains no moisture

Question 16

How many BTU’s does it take to raise one pound of water at 32®F to the boiling point at 14.7 psia and then to steam

Answer 16

180 BTU’s to raise one pound of water at 32®F to the boiling point and an additional 970 BTU’s to create steam for a total of 1150 BTU’s.

Question 17

What is meant by heat being transmitted by radiation? By conduction? By convection

Answer 17

Radiant- heat transferred by light waves without a material carrier

Convection- heat transferred by currents in a fluid

Conduction- heat transferred molecule to molecule

Question 18

What is meant by the saturated steam temperature? What is heat of vaporization

Answer 18

Saturated steam temperature is the temperature corresponding to its pressure and contains no moisture. Heat of evaporation is the amount of heat energy which changes from liquid to gas (latent heat)

Question 19

What is wet steam, and how is the enthalpy of wet steam calculated?

Answer 19

Wet steam is a mix of steam and water which can be found in values in steam table.

Question 20

What is superheated steam, and what does degrees of superheat mean

Answer 20

Superheated steam is steam at a temperature above that of dry saturated steam at the same pressure. Degrees of superheat would be the number of degrees higher the steam is to the temperature corresponding to its pressure

Question 21

What are the advantages of using superheated steam

Answer 21

Travels long distance with no condensate, no moisture, and higher heat content and more efficient.

Question 22

What device measures absolute pressure

Answer 22

Barometer

Question 23

What is a pyrometer used for

Answer 23

Temperature measurement

Question 24

What is a manometer used for

Answer 24

Measure draft

Question 25

TON OF REFRIGERATION

Answer 25

IS THE MELTING OF ONE TON OF
ICE (2,000 LBS.) IN 24 HOURS

2,000 X 144 = 288,000 BTU/DAY
144 = LATENT HEAT OF FUSION

288,000 = 12,000 BTU/HR

Question 26

What is enthalpy

Answer 26

The total heat content of a substance expressed as btu/lb

Hf = enthalpy of fluid
Hfg = enthalpy of latent heat
Hg = enthalpy of gas/vapor

formula
Hf+Hfg = Hg

Question 27

What is the first law of thermodynamics

Answer 27

Energy can not be created or destroyed but may be converted from one form to another

Question 28

What is the 2nd law of thermodynamics

Answer 28

No machine actual or ideal can both continuously and completely transfer heat into mechanical energy. nothing is 100% efficient

Question 29

What is latent heat of fusion

Answer 29

heat that is added to a solid that causes a change of state to a liquid. ( one lb of ice @ 32 deg f becomes one lb of water at 32 deg f when 144 btu’s are added)

Question 30

What is latent heat of evaporation

Answer 30

Heat added to a liquid that causes a change of state to a gas/vapor. ( one lb of water at 212 deg f becomes one lb of steam at 212 deg f when 970.3 btu’s are added

Question 31

What is specific gravity

Answer 31

The weight of any substance when compared to water

Question 32

What is specific volume

Answer 32

the volume of any substance when compared to water cu ft/lb

Question 33

Fuel oil with a specific gravity of 0.89, what is the weight

Answer 33

Multiply 8.33 by .89 to get the weight.

8.33 x .89 = 7.41

Question 34

What are the 7 lines on a mollier chart

Answer 34

Lines of constant enthalpy
Lines of constant entropy
lines of constant temperature
Lines of constant pressure
Lines of constant quality
Saturation line
Degree of superheat
Standard atmosphere

Question 35

What is a mollier chart

Answer 35

The steam tables in graph form plotted in XY coordinates