Review Questions Flashcards
Summarize the 1st and 2nd laws of Thermodynamics
A. 1st law-Energy cannot be created or destroyed. 2nd law-Heat travels from low temperature to high temperature
B. 1st law-Energy cannot be created or destroyed. 2nd law-Heat travels from high temperature to low temperature
C. 1st law-Energy can be created and destroyed. 2nd law-Heat travels from low temperature to high temperature
D. 1st law-Energy can be created and destroyed. 2nd law- Heat travels from high temperature to low temperature
B. 1st law-Energy can not be created or destroyed. 2nd law-Heat travels from high temperature to low temperature
How does temperature difference affect the rate that heat travels?
A. Temperature difference does not affect the rate heat travels.
B. The greater the temperature difference, the slower the heat transfer.
C. The greater the temperature difference, the faster the heat transfer.
D. The effect of temperature difference is tied to atmospheric pressure.
C. The greater the temperature difference, the faster the heat transfer
Conduction is heat transfer by direct contact from molecule to molecule. When a metal rod is heated on one end, heat travels from that end to the cooler end through the rod. Radiation is heat transfer by circulating a fluid to distribute the heat. The air circulating inside older refrigerators is an example of natural convection. Convection is heat transfer by waves of electromagnetic radiation. Being heated by fire is an example of radiant heat.
A. True
B. False
B. False
What is the relationship between electrical conductivity and thermal conductivity?
A. Materials that make good electrical conductors do not make good thermal conductor’s.
B. There is no relationship.
C. Materials that make good electrical conductors also tend to make good thermal conductors
C. Materials that make good electrical conductors also tend to make good thermal conductors
List two materials that are considered to be good thermal conductor’s
A. Tin and aluminum
B. Wood and copper
C. Tin and lead
D. Copper and aluminum
D. Copper and aluminum
According to their K value, which material is a better insulator?
A. Expanded polystyrene
B. Expanded polyurethane
A. Expanded polystyrene
Explain why the addition of fins on the tubing will increase the rate of heat transfer
A. Fins added to tubing decrease the service area. The decreased surface area can transfer more heat because of more contact between the coil in the air
B. Fins added to tubing increase the surface area. The increase surface area can transfer more heat because of more contact between the coil in the air
C. Fins added to tubing increase the surface area. The increased surface area transfers less heat because of less contact between the coil in the air
D. Fins added to tubing increase the surface area. The increased the surface area transfers less heat because of more contact between the coil in the air
B. Fins added to tubing increase the surface area. The increase surface area can transfer more heat because of more contact between oil in the air
Natural convection occurs because of differences in fluid density. In a room with a heat source near the floor, warm air is less dense and rises. It gives off some of its heat, cools, and becomes denser, and falls back down. This establishes a natural convection circulation pattern.
A. True
B. False
A. True
What factors determine the amount of radiant energy that is transferred between two objects?
A. The frequency of the radiation
B. The absolute temperature of the source
C. The surface area of the source
D. The distance between the source and the sink
E. All of the above
E. All of the above
In regards to the relationship between radiant energy and color, the primary frequency emitted by an object changes with the absolute temperature of the object. When the primary frequency is within the visible light spectrum, the object appears that color.
A. True
B. False
A. True
Can a substance change temperature and state at the same time?
A. Yes
B. No
B. No
Changing from liquid to solid when heat is removed from a liquid is called fusion. Changing from a solid to liquid when heat is added to a solid is called liquefication. Changing from liquid to gas when heat is added to a liquid is called vaporization. Changing from gas to a liquid when heat is removed from a gas is called condensation. Changing from a gas to a solid without going through the liquid state is called deposition. Changing from a solid to a gas without going through the liquid state is called \_\_\_\_\_\_\_\_\_? A. The critical point B. The optimization Point C. The boiling point D. Sublimation
D. Sublimation
The sensible heat process causes a change in temperature.
A. True
B. False
A. True
The latent heat of fusion is the amount of heat that must be added to a pound of liquid to change it to a solid.
A. True
B. False
A. True
The saturation pressure temperature chart correlates the pressure and temperatures of saturated mixes. It shows the boiling point of a refrigerant for any given pressure.
A. True
B. False
A. True
The refrigerant R-22 is a system component has a pressure of 70 psig and a temperature of 50°F it is _______?
A. Saturated
B. Superheated
C. Subcooled
A. Superheated
The refrigerant R-134a in a system component has a pressure of 35 psig a temperature of 40°F it is _________?
A. Saturated
B. Superheated
C. Subcooled
A. Saturated
The refrigerant R-410a in a system component has a pressure of 340 psig and a temperature of 95°F it is _______?
A. Saturated
B. Superheated
C. Subcooled
C. Subcooled
Refrigeration gauges read in psig and are calibrated to read 1 at atmospheric pressure. Changes in atmospheric pressure can change the calibration point and affect the final reading.
A. True
B. False
B. False
A fluid is a substance that deforms and flows under pressure. Examples are liquids and gases.
A. True
B. False
A. True
Define pressure:
A. Mass per Unit Area
B. Force per Unit Area squared
C. Atmospheric Conditions per Unit Area
D. Force per Unit Area
D. Force per Unit Area
Atmospheric pressure is created by the weight of the air in the atmosphere.
A. True
B. False
A. True
What is the missing number in the following question and answer?
Q. What is the difference between absolute pressure and gauge pressure?
A. Absolute pressure starts at the perfect vacuum, no pressure, and goes up. ______ on an absolute pressure scale is the lowest possible reading. Gauge pressure uses the atmospheric pressure as it’s starting point. Typically 14.7 psia = ________psig
A. 2
B. 1
C. 0
D. -1
C. 0
Which of the following causes atmospheric pressure to change?
A. Altitude
B. Temperature
C. Humidity
D. Only altitude and temperature
E. All of the above
E. All of the above
What is the relationship between atmospheric pressure and barometric pressure?
A. Barometric pressure is only used at sea, while atmospheric pressure is used on land
B. Atmospheric pressure is never the same as barometric pressure
C. They are essentially two terms for the same thing
D. Atmospheric pressure, when added to barometric pressure, gives the refrigeration pressure
C. They are essentially two terms for the same thing
The reading on a low side pressure gauge is 65 psig. What is the absolute pressure?
A. 100 psia or 99.7 psia
B. 90 psia or 89.7 psia
C. 80 psia or 79.7 psia
D. 70 psia or 69.7 psia
C. 80 psia or 79.7 psia
Convert a chart reading of 100 psia to the reading you would see in gauge pressure.
A. 100 psia - 15 = 85 psig
B. 100 psia - 10 = 90 psig
C. 100 psia + 15 = 115 psig
D. 100 psia + 10 = 110 psig
A. 100 psia - 15 = 85 psig
Convert a barometric pressure reading of 26 inches HG to psia
A. 26 in HG /2 +15=28 psia
B. 26 in HG/10=2.6 psia
C. 26 in HG/2=13 psia
D. 26 in HG+15=41 psia
C. 26 in HG/2=13 psia
Convert a reading of 20 inches HG vacuum to psia
A. 20 psia
B. 10 psia
C. 5 psia
D. 2.5 psia
C. 5 psia
A vacuum is any pressure more than atmospheric pressure. Mercury columns can be used to measure vacuum by measuring how much pressure has been removed.
A. True
B. False
B. False
Liquid column pressures are expressed in inches of mercury for smaller pressures, like the air pressure in duct work or gas line pressure. They are expressed in inches of water for larger pressures, like atmospheric pressure or vacuum pressure.
A. True
B. False
B. False
Which of the following is true?
A. Fluid pressure is created by the weight of the fluid
B. The deeper the fluid, the higher the pressure
C. Both of the above
D. None of the above
C. Both of the above
What is the pressure at the bottom of a square tank that has a cross section of 15ft square and is filled with water to a depth of 4 ft?
A. 4 psi
B. 2.732 psi
C. 0.433 psi
D. 1.732 psi
D. 1.732 psi
What is the pressure in psi required to lift water 15 feet?
A. 15.495 psi
B. 6.495 psi
C. 15.433 psi
D. 6.433 psi
B. 6.495 psi
A simple open arm manometer measures pressure by the pressure pushing on one side of the manometer, forcing the liquid in that side of the manometer down and raising the level of the liquid on the other side. The pressure reading is the difference between the two liquid levels.
A. True
B. False
A. True
What type of gauge has an oval metal tube that is curved along its length and forms an almost complete circle? One end of the tube is closed, and the other end is connected to the pressure being tested. When pressure is applied to the open end, the tube tends to straighten. This motion moves the gauge needle.
A. Simple gauge
B. Compound gauge
C. Pressure gauge
D. Bourbon tube gauge
D. Bourbon tube gauge
This law states: the total pressure in a mixture of gasses is equal to the sum of all the individual gas pressures.
A. Dalton’s Law
B. Boyle’ Law
C. Charles’ Law
D. Pascal’s Law
A. Dalton’s Law
What temperature in degrees Fahrenheit would a fixed volume of gas need to be heated to in order to double its pressure if it starts out at 25°F
A. 50
B. 485
C. 510
D. 975
A. 50
Bars are used in many Pressure applications by countries on the SI system. 10 bars are approximately equal to atmospheric pressure. It is exactly equal to 100 kilopascales
A. True
B. False
B. False
Which is a larger unit of pressure?
A. 1 kilopascale
B. 1 psi
B. 1 psi
