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UNIT 9 REVIEW QUESTIONS ANSWER KEY GO BACK TO INDEX
9-1) What is temperature?
9-2) What is the first color of light that can be seen when a piece of metal is being
heated?
9-3) How does a glass stem thermometer measure temperature?
9-4) What causes the pointer to move on a dial type thermometer?
9-5) What is an advantage of digital thermometers?
9-6) Which type thermometer can see the temperature of a surface from a distance?
9-7) What two metals are joined to create a Type K thermocouple?
9-8) What are the two points used to create the Celsius temperature scale?
9-9) The Rankin temperature scale uses the same spacing between degrees as
which other system?
9-10) Convert the following Celsius temperatures to Fahrenheit.
a. 50oC50 x 1.8 = 90 90+32=122°F
9-11) Convert the following Fahrenheit temperatures to Celsius.
a. 50oF50 – 32 = 18 18 / 1.8 = 10°C
9-12) Convert the following temperatures.
a. – 60 F to Rankine -60 + 460 = 400°R
9-13) Convert the following temperatures.
a. 125oK to Rankine 125 x 1.8 = 225°R
9-14) Summarize the first and second laws of thermodynamics.
9-15) How does temperature difference affect the rate heat travel?
9-16) List the three methods of heat transfer and give an example of each.
1. Conduction – heat transfer by direct contact form molecule to molecule.
2. Convection – heat transfer by circulating a fluid to distribute the heat.
3. Radiation- heat transfer by waves of electromagnetic radiation. Being
heated by a fire is an example of radiant heat.
9-17) List two materials that are considered to be good thermal conductors.
9-18) According to their k values, which material is a better insulator: expanded
polystyrene or expanded polyurethane?
9-19) Explain why the addition of fins on the tubing will increase the rate of heat
transfer.
9-20) Describe the process of natural convection.
Natural convection occurs because of differences in fluid density. In a room
24
9-21) What factors determine the amount of radiant energy that is transferred
between two objects?
9-22) Explain the relationship between radiant energy and color.
9-23) Describe the following terms: fusion, liquefaction, vaporization,
condensation, deposition, and sublimation.
Fusion - changing from liquid to solid when heat is removed from a liquid
9-24) Define sensible heat.
9-25) Define latent heat.
9-26) What is a saturation pressure-temperature chart?
9-27) The refrigerant R-22 in a system component has a pressure of 70 psig and a
temperature of 50°F. Is it saturated, superheated, or subcooled?
9-28) The refrigerant R-134a in a system component has a pressure of 35 psig and a
temperature of 40°F. Is it saturated, superheated, or subcooled?
9-29) The refrigerant R-410a in a system component has a pressure of 340 psig and a
temperature of 95°F. Is it saturated, superheated, or subcooled?
25
9-30) Calculate the amount of heat in BTUs required to change the temperature of 6
pounds of copper from 75°F to 100°F.
9-31) Calculate the amount of heat in BTUs required to change 5 pounds of 10°F
ice to 242°F steam?
The heat required to increase the temperature of 5 pounds of ice from 10
q
F
to 32
q
F is calculated using the specific heat formula:
The heat required to melt 5 pounds of ice is calculated using the latent heat
formula:
The heat required to increase the temperature of 5 pounds of water from
32
q
F to 212
q
F is calculated using the specific heat formula:
The heat required to boil 5 pounds of water is calculated using the latent
heat formula:
The heat required to increase the temperature of a pound of steam from 212
q
F
to 242
q
F is calculated using the specific heat formula:
