2
RETA Industrial Refrigeration Book 2 (Exam Revision) questions with
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verified detailed answers || ||
Which of the following factors listed below does not affect heat transfer?
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(pg. 1-2) ||
A) Temperature Difference
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B) Surface Area
|| ||
C) Thermal Conductivity
|| ||
D) Density - ✔✔D) Density
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An example of a poor conductor of heat is? (pg. 1-3)
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A) Aluminum Tubing
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B) Schedule 40 Steel Pipe
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C) Wood
||
D) Water - ✔✔C) Wood
|| || || ||
Thermal conductivity ('K') is? (pg. 1-3)
|| || || || ||
A) Exactly the same for any metal
|| || || || || ||
B) The number of BTU's that will pass in 1 hour through a material 1" thick with an area of
|| || || || || || || || || || || || || || || || || || || ||
1 sq. ft. if the temperature difference from one side to the other is 1°F
|| || || || || || || || || || || || || ||
C) A measure of the total energy (heat content) per pound of refrigerant measured in BTU's
|| || || || || || || || || || || || || || ||
D) A relationship between heat and temperature that is useful in determining discharge
|| || || || || || || || || || || || ||
temperatures. It is heat moved into or out of the process, divided by the absolute
|| || || || || || || || || || || || || || ||
temperature in BTU's/pound/R - ✔✔B) The number of BTU's that will pass in 1 hour
|| || || || || || || || || || || || || || ||
through a material 1" thick with an area of 1 sq. ft. if the temperature difference from one
|| || || || || || || || || || || || || || || || || ||
side to the other is 1°F
|| || || || ||
,2
Which is NOT a common source of fouling of a heat exchange surface?
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(pg. 1-7)
||
A) Water
||
B) Oil
||
C) Frost
||
D) Dirt - ✔✔A) Water
|| || || ||
Which statement is true? (pg. 1-3)
|| || || || ||
A) The higher the 'k' factor, the greater the thermal conductivity
|| || || || || || || || || ||
B) The lower the 'k' factor, the greater the thermal conductivity
|| || || || || || || || || ||
C) The higher the 'k' factor, the lower the thermal conductivity
|| || || || || || || || || ||
D) The 'k' factor is not associated with thermal conductivity - ✔✔A) The higher the 'k'
|| || || || || || || || || || || || || || || ||
factor, the greater the thermal conductivity
|| || || || ||
Optimum 'U' factor for the given material that the heat exchanger is made of results when?
|| || || || || || || || || || || || || || || ||
(pg. 1-7/8)
||
A) There is no impeding substance such as ice, dirt, or oil on the surfaces of the heat
|| || || || || || || || || || || || || || || || || ||
exchanger tubes ||
B) Maximum airflow across the evaporator is achieved
|| || || || || || ||
C) The system is operating with the design recirculation low
|| || || || || || || || ||
D) The system is maintaining temperature - ✔✔A) There is no impeding substance such as
|| || || || || || || || || || || || || || ||
ice, dirt, or oil on the surfaces of the heat exchanger tubes
|| || || || || || || || || || ||
When air flow is decreased across a heat exchange surface, cooling capacity is? (pg. 1-10)
|| || || || || || || || || || || || || ||
A) Reduced
||
B) Increased
||
C) Not changed because area is not changed
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,2
D) Not changed because evaporator temperature is not changed - ✔✔A) Reduced
|| || || || || || || || || || ||
Centrifugal fans have an advantage over propeller fans in that they ______________ than
|| || || || || || || || || || || || ||
prop fans? (pg. 1-12)
|| || ||
A) Require less physical space
|| || || ||
B) Consume more hp per CFM of air moved
|| || || || || || || ||
C) Are quieter
|| ||
D) Have fewer components to maintain - ✔✔C) Are quieter
|| || || || || || || || ||
The operating engineer? (pg. 1-7)
|| || || ||
A) Cannot change the 'k' factor of the metal but has some control of the overall 'U' factor
|| || || || || || || || || || || || || || || || || ||
for the evaporator as a unit
|| || || || ||
B) Can increase 'k' factor by increasing the air velocity over the evaporator and has some
|| || || || || || || || || || || || || || || ||
control of the overall 'U' factor for the evaporator as a unit
|| || || || || || || || || || ||
C) Should allow frost to collect on the evaporator increase 'k' factor
|| || || || || || || || || || ||
D) Can increase 'k' factor by starting another compressor - ✔✔A) Cannot change the 'k'
|| || || || || || || || || || || || || || ||
factor of the metal but has some control of the overall 'U' factor for the evaporator as a
|| || || || || || || || || || || || || || || || || ||
unit
The limiting factor of an evaporator's capacity that the operator cannot control is? (pg. 1-7)
|| || || || || || || || || || || || || ||
A) Suction Temperature
|| ||
B) Suction Pressure
|| ||
C) Evaporator Size
|| ||
D) Refrigerant Liquid Feed Flow - ✔✔C) Evaporator Size
|| || || || || || || ||
The best way to keep an evaporator from being affected by oil build-up is to? (pg. 1-8)
|| || || || || || || || || || || || || || || ||
A) Operate the system at the correct evaporator temperature
|| || || || || || || ||
B) Periodically remove oil from the oil collection points
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, 2
C) Set hot gas defrost cycle for a minimum of 30 minutes
|| || || || || || || || || || ||
D) Increase air flow across the evaporators - ✔✔B) Periodically remove oil from the oil
|| || || || || || || || || || || || || || ||
collection points ||
The effectiveness of a heat transfer surface depends on several factors. One factor the
|| || || || || || || || || || || || || ||
operator has control over is? (pg. 1-8)
|| || || || || ||
A) Evaporator surface area
|| || ||
B) Material the evaporator is made of
|| || || || || ||
C) Type of fans used
|| || || ||
D) Cleanliness of the evaporator - ✔✔D) Cleanliness of the evaporator
|| || || || || || || || || ||
One advantage of using axial type fans is? (pg. 1-12)
|| || || || || || || || ||
A) Quieter operation
|| ||
B) They require less motor horsepower per CFM
|| || || || || || ||
C) They can move air further across the space to be cooled
|| || || || || || || || || || ||
D) They can work against a higher static pressure - ✔✔B) They require less motor
|| || || || || || || || || || || || || || ||
horsepower per CFM || ||
Which of the following is NOT a result of scale build-up on a condenser coil? (pg. 1-13)
|| || || || || || || || || || || || || || || ||
A) Reduced heat transfer
|| || || ||
B) Increased operating cost
|| || ||
C) Increased 'U' value
|| || ||
D) Increased condensing temperatures - ✔✔C) Increased 'U' value
|| || || || || || || ||
If 'R' value is doubled, what will happen to the heat transfer rate (assuming the
|| || || || || || || || || || || || || || ||
temperature difference and the area do not change)? (pg. 1-13) || || || || || || || || ||
A) The rate of heat that is transferred will be double
|| || || || || || || || || ||
RETA Industrial Refrigeration Book 2 (Exam Revision) questions with
|| || || || || || || || ||
verified detailed answers || ||
Which of the following factors listed below does not affect heat transfer?
|| || || || || || || || || || ||
(pg. 1-2) ||
A) Temperature Difference
|| ||
B) Surface Area
|| ||
C) Thermal Conductivity
|| ||
D) Density - ✔✔D) Density
|| || || ||
An example of a poor conductor of heat is? (pg. 1-3)
|| || || || || || || || || ||
A) Aluminum Tubing
|| ||
B) Schedule 40 Steel Pipe
|| || || ||
C) Wood
||
D) Water - ✔✔C) Wood
|| || || ||
Thermal conductivity ('K') is? (pg. 1-3)
|| || || || ||
A) Exactly the same for any metal
|| || || || || ||
B) The number of BTU's that will pass in 1 hour through a material 1" thick with an area of
|| || || || || || || || || || || || || || || || || || || ||
1 sq. ft. if the temperature difference from one side to the other is 1°F
|| || || || || || || || || || || || || ||
C) A measure of the total energy (heat content) per pound of refrigerant measured in BTU's
|| || || || || || || || || || || || || || ||
D) A relationship between heat and temperature that is useful in determining discharge
|| || || || || || || || || || || || ||
temperatures. It is heat moved into or out of the process, divided by the absolute
|| || || || || || || || || || || || || || ||
temperature in BTU's/pound/R - ✔✔B) The number of BTU's that will pass in 1 hour
|| || || || || || || || || || || || || || ||
through a material 1" thick with an area of 1 sq. ft. if the temperature difference from one
|| || || || || || || || || || || || || || || || || ||
side to the other is 1°F
|| || || || ||
,2
Which is NOT a common source of fouling of a heat exchange surface?
|| || || || || || || || || || || || ||
(pg. 1-7)
||
A) Water
||
B) Oil
||
C) Frost
||
D) Dirt - ✔✔A) Water
|| || || ||
Which statement is true? (pg. 1-3)
|| || || || ||
A) The higher the 'k' factor, the greater the thermal conductivity
|| || || || || || || || || ||
B) The lower the 'k' factor, the greater the thermal conductivity
|| || || || || || || || || ||
C) The higher the 'k' factor, the lower the thermal conductivity
|| || || || || || || || || ||
D) The 'k' factor is not associated with thermal conductivity - ✔✔A) The higher the 'k'
|| || || || || || || || || || || || || || || ||
factor, the greater the thermal conductivity
|| || || || ||
Optimum 'U' factor for the given material that the heat exchanger is made of results when?
|| || || || || || || || || || || || || || || ||
(pg. 1-7/8)
||
A) There is no impeding substance such as ice, dirt, or oil on the surfaces of the heat
|| || || || || || || || || || || || || || || || || ||
exchanger tubes ||
B) Maximum airflow across the evaporator is achieved
|| || || || || || ||
C) The system is operating with the design recirculation low
|| || || || || || || || ||
D) The system is maintaining temperature - ✔✔A) There is no impeding substance such as
|| || || || || || || || || || || || || || ||
ice, dirt, or oil on the surfaces of the heat exchanger tubes
|| || || || || || || || || || ||
When air flow is decreased across a heat exchange surface, cooling capacity is? (pg. 1-10)
|| || || || || || || || || || || || || ||
A) Reduced
||
B) Increased
||
C) Not changed because area is not changed
|| || || || || || ||
,2
D) Not changed because evaporator temperature is not changed - ✔✔A) Reduced
|| || || || || || || || || || ||
Centrifugal fans have an advantage over propeller fans in that they ______________ than
|| || || || || || || || || || || || ||
prop fans? (pg. 1-12)
|| || ||
A) Require less physical space
|| || || ||
B) Consume more hp per CFM of air moved
|| || || || || || || ||
C) Are quieter
|| ||
D) Have fewer components to maintain - ✔✔C) Are quieter
|| || || || || || || || ||
The operating engineer? (pg. 1-7)
|| || || ||
A) Cannot change the 'k' factor of the metal but has some control of the overall 'U' factor
|| || || || || || || || || || || || || || || || || ||
for the evaporator as a unit
|| || || || ||
B) Can increase 'k' factor by increasing the air velocity over the evaporator and has some
|| || || || || || || || || || || || || || || ||
control of the overall 'U' factor for the evaporator as a unit
|| || || || || || || || || || ||
C) Should allow frost to collect on the evaporator increase 'k' factor
|| || || || || || || || || || ||
D) Can increase 'k' factor by starting another compressor - ✔✔A) Cannot change the 'k'
|| || || || || || || || || || || || || || ||
factor of the metal but has some control of the overall 'U' factor for the evaporator as a
|| || || || || || || || || || || || || || || || || ||
unit
The limiting factor of an evaporator's capacity that the operator cannot control is? (pg. 1-7)
|| || || || || || || || || || || || || ||
A) Suction Temperature
|| ||
B) Suction Pressure
|| ||
C) Evaporator Size
|| ||
D) Refrigerant Liquid Feed Flow - ✔✔C) Evaporator Size
|| || || || || || || ||
The best way to keep an evaporator from being affected by oil build-up is to? (pg. 1-8)
|| || || || || || || || || || || || || || || ||
A) Operate the system at the correct evaporator temperature
|| || || || || || || ||
B) Periodically remove oil from the oil collection points
|| || || || || || || ||
, 2
C) Set hot gas defrost cycle for a minimum of 30 minutes
|| || || || || || || || || || ||
D) Increase air flow across the evaporators - ✔✔B) Periodically remove oil from the oil
|| || || || || || || || || || || || || || ||
collection points ||
The effectiveness of a heat transfer surface depends on several factors. One factor the
|| || || || || || || || || || || || || ||
operator has control over is? (pg. 1-8)
|| || || || || ||
A) Evaporator surface area
|| || ||
B) Material the evaporator is made of
|| || || || || ||
C) Type of fans used
|| || || ||
D) Cleanliness of the evaporator - ✔✔D) Cleanliness of the evaporator
|| || || || || || || || || ||
One advantage of using axial type fans is? (pg. 1-12)
|| || || || || || || || ||
A) Quieter operation
|| ||
B) They require less motor horsepower per CFM
|| || || || || || ||
C) They can move air further across the space to be cooled
|| || || || || || || || || || ||
D) They can work against a higher static pressure - ✔✔B) They require less motor
|| || || || || || || || || || || || || || ||
horsepower per CFM || ||
Which of the following is NOT a result of scale build-up on a condenser coil? (pg. 1-13)
|| || || || || || || || || || || || || || || ||
A) Reduced heat transfer
|| || || ||
B) Increased operating cost
|| || ||
C) Increased 'U' value
|| || ||
D) Increased condensing temperatures - ✔✔C) Increased 'U' value
|| || || || || || || ||
If 'R' value is doubled, what will happen to the heat transfer rate (assuming the
|| || || || || || || || || || || || || || ||
temperature difference and the area do not change)? (pg. 1-13) || || || || || || || || ||
A) The rate of heat that is transferred will be double
|| || || || || || || || || ||
