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 - ANSWER-D) Density
An example of a poor conductor of heat is? (pg. 1-3)
A) Aluminum Tubing
B) Schedule 40 Steel Pipe
C) Wood
...
RETA Industrial
Refrigeration Book 2
(2013
Revision)Questions &
Answers 100% Correct
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 - ANSWER-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 - ANSWER-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 - ANSWER-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
Which is NOT a common source of fouling of a heat exchange surface?
(pg. 1-7)
A) Water
B) Oil
C) Frost
D) Dirt - ANSWER-A) Water
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 - ANSWER-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
D) Not changed because evaporator temperature is not changed - ANSWER-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 - ANSWER-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 - ANSWER-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) 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 - ANSWER-A) The higher the 'k' factor,
the greater the thermal conductivity
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
C) Set hot gas defrost cycle for a minimum of 30 minutes
D) Increase air flow across the evaporators - ANSWER-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 - ANSWER-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 - ANSWER-B) They require less motor horsepower
per CFM
What happens to the theoretical capacity of an evaporator in a 0°F freezer if the ammonia
evaporating pressure is dropped from 8.96 PSIG to 6.11 PSIG? (pg.
A) The capacity of the evaporator is reduced by 50%
B) The capacity of the evaporator is doubled
C) The capacity of the evaporator is not changed
D) The capacity of the evaporator is increased by 50% - ANSWER-C) The capacity of the evaporator is
not changed
Damaged insulation on the suction line in an ammonia refrigeration system will? (pg. 1-14)
A) Not change the efficiency of the system because suction pressure will not change
B) Cause efficiency loss and potential damage to the suction line
C) Look bad but will not cause any major problems
D) Cause an efficiency loss but will not cause any other problems - ANSWER-B) Cause efficiency loss
and potential damage to the suction line
Enthalpy is? (pg. 2-2)
A) A measure of total energy (heat content) per pound of refrigerant measured in BTU's
B) The net heat absorbing capacity of the refrigerant after the point of expansion
C) The amount of cooling effect that can be obtained from a refrigeration system
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