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RETA Industrial Refrigeration Book 2 Exam
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Which of the following does NOT happen when the cooling load is increased on a system using a dry expansion evaporator? A) The boiling rate increases B) The rate at which vapor is produced increases C) The compressor will have to move more vapor or the pressure in the evaporator will rise D) The TXV will respond by reducing the refrigerant flow to the coil --------- CORRECT ANSWER-----------------D) The TXV will respond by reducing the refrigerant flow to the coil What is the purpose of a suction line accumulator? (pg. 5-10) A) Suction line accumulators store refrigerant for use in the evaporator when the receiver is offline B) Suction line accumulators reduce pressure fluctuations in the evaporator coils C) Suction line accumulators collect liquid that passes through a dry expansion evaporator D) Suction line accumulators return oil to the compressor crankcase --------- CORRECT ANSWER-----------------C) Suction line accumulators collect liquid that passes through a dry expansion evaporator
A pumped liquid recirculation system sends 15°F liquid Ammonia out to the system. The piping goes up to and over the roof, 21 feet above the pump outlet. The pump discharge pressure is 45 PSIG. The pressure of the liquid in the pipe at the roof is? (pg. 6-6) A) Approximately 45 PSIG B) Approximately 39 PSIG C) Approximately 51 PSIG D) Saturated ---------CORRECT ANSWER-----------------B) Approximately 39 PSIG "Liquid pressure at the top of a 21' vertical rise will be approximately 6 PSIG less than the pressure measured at the base of the rise" Carry over to the compressor is minimized in the pumped liquid overfeed system because? (pg. 6-37) A) The low-side float B) The liquid line design C) The recirculator D) The liquid pump ---------CORRECT ANSWER-----------------C) The recirculator Liquid is forced out of the drum of a gas 'double pumper drum' system to the evaporator by means of? (pg. 6-21) A) High-pressure vapor B) Bulb pressure in the power element
B) Oil migrates towards high-pressure with Ammonia and low-pressure with halocarbons C) Oil migrates towards low-pressure with Ammonia and high-pressure with halocarbons D) Oil rises toward the top with Ammonia and settles to the bottom with halocarbons ---------CORRECT ANSWER-----------------A) Oil settles to the bottom with Ammonia and rises to the top with halocarbons A 3:1 recirculation ratio means that the wet suction return line contains? (pg. 6-4/51) A) 3 parts liquid, 1 part vapor B) 1 part liquid, 3 parts vapor C) 2 parts liquid, 1 part vapor D) 4 parts liquid, 1 part vapor ---------CORRECT ANSWER-----------------C) 2 parts liquid, 1 part vapor (3 to 1 means for every 3 quantities of liquid supplied, 1 will turn to vapor. Therefore, in the return line, there would be 2 quantities of liquid and 1 quantity of vapor) Compared with top fed evaporators, the overfeed ratio for bottom feed evaporators is? (pg. 6-33) A) Greater B) The same C) Lower D) None ---------CORRECT ANSWER-----------------C) Lower
In a double pumper drum system, what happens when the pumper drum is filled? (pg. 6-21) A) Liquid stops returning to the recirculator B) Flow is stopped from the high-pressure receiver C) The compressor shuts down D) Flow from the recirculator stops ---------CORRECT ANSWER-----------------D) Flow from the recirculator stops What happens to flash gas in a pumped liquid overfeed system? (pg. 6-49) A) It goes through the recirculator to the compressor B) It goes directly to the evaporator C) There is no flash gas in an overfeed system D) It is used to power the pumper drum to circulate liquid Ammonia --------- CORRECT ANSWER-----------------A) It goes through the recirculator to the compressor Why does the liquid overfeed system require less evaporator surface than a DX evaporator of the same capacity? (pg. 6-49) A) Less refrigerant passes through the evaporator B) The evaporator tubes are smaller C) The evaporator tubes are larger
(pg. 6-48) A) The recirculator B) The oil separator C) The suction line accumulator D) The condenser outlet ---------CORRECT ANSWER-----------------A) The recirculator Which of the following is not a problem associated with migrating oil in a system? (pg. 6-48/49) A) Inefficient operation of evaporators B) Loss of lubrication in the compressor C) Reduction of system capacity D) Low condensing pressure ---------CORRECT ANSWER-----------------D) Low condensing pressure What precaution must be exercised in placing a check valve in any liquid line? (pg. 6 - 44) A) The check valve should be at least one line size larger B) The check valve must have a bypass line C) Positive closing of the downstream line must be possible D) That no liquid refrigerant can be trapped ---------CORRECT ANSWER----------------
- D) That no liquid refrigerant can be trapped What is NOT a requirement of a properly sized recirculator? (pg. 6-37)
A) It must be able to hold all surges from the evaporators B) It must be able to hold all of the system's refrigerant C) It must keep pump suction flooded D) It must prevent liquid from passing through to the compressor ---------CORRECT ANSWER-----------------B) It must be able to hold all of the system's refrigerant Gravity flooded evaporators have greater heat transfer capability than dry expansion evaporators of the same size and surface area because? (pg. 7-2) A) They are completely filled with liquid B) More of the heat transfer surface is wetted C) Vapor is flowing at a higher velocity D) There is more evaporator surface ---------CORRECT ANSWER-----------------B) More of the heat transfer surface is wetted The gravity flooded evaporator, in some applications, can have a higher recirculation ratio than forced liquid overfeed systems because of? (pg. 7-4) A) The accumulator B) Pumped flow C) No expansion valve D) Thermosyphon action ---------CORRECT ANSWER-----------------D) Thermosyphon action Oil should be drained from a gravity flooded Ammonia system evaporator?
Excess oil in the low-side of a gravity flooded halocarbon refrigerant system accumulates? (pg. 7-7) A) In the suction accumulator B) Below the refrigerant C) Near the top of the refrigerant level D) Excess oil does not accumulate in the low-side of a gravity flooded halocarbon refrigerant system ---------CORRECT ANSWER-----------------C) Near the top of the refrigerant level 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 ---------CORRECT 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 ---------CORRECT 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 ---------CORRECT 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 ---------CORRECT ANSWER-----------------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
A) Require less physical space B) Consume more hp per CFM of air moved C) Are quieter D) Have fewer components to maintain ---------CORRECT 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 ---------CORRECT 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) Suction Temperature B) Suction Pressure C) Evaporator Size D) Refrigerant Liquid Feed Flow ---------CORRECT ANSWER-----------------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 C) Set hot gas defrost cycle for a minimum of 30 minutes D) Increase air flow across the evaporators ---------CORRECT 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 ---------CORRECT 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 ---------CORRECT ANSWER--------- --------B) They require less motor horsepower per CFM
D) The capacity of the evaporator is increased by 50% ---------CORRECT 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 ---------CORRECT 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 D) Heat that cannot be measured through a change in temperature --------- CORRECT ANSWER-----------------A) A measure of total energy (heat content) per pound of refrigerant measured in BTU's The enthalpy diagram? (pg. 2-6)
A) Illustrates the changes of condition and heat content of a pound of refrigerant at different points of the refrigeration cycle B) Illustrates the total heat transfer capacity of the system from evaporators through condensers in tons of refrigeration C) Utilizes two scales, pressure and tons of refrigeration D) Does not take into account the effect of flash gas ---------CORRECT ANSWER----- ------------A) Illustrates the changes of condition and heat content of a pound of refrigerant at different points of the refrigeration cycle The enthalpy diagram has three regions of refrigerant condition which are? (pg. 2-
A) Solid, Liquid and Gas B) Subcooled Liquid, SAT Liquid and Vapor, and Superheated Vapor C) Hot, Medium, and Cold D) Flash Gas, Subcooled Liquid, Subcooled Liquid and Flash Gas ---------CORRECT ANSWER-----------------B) Subcooled Liquid, SAT Liquid and Vapor, and Superheated Vapor The pressure scale on an enthalpy diagram typically used in the U.S. is expressed in? (pg. 2-8) A) Kilopascals B) PSIG C) PSIA D) Newtons ---------CORRECT ANSWER-----------------C) PSIA
The temperature lines within the saturated mixture dome of an enthalpy diagram? (pg. 2-10) A) Are horizontal because change of state of a refrigerant at constant pressure is done at a constant temperature B) Are vertical because change of state of a refrigerant at constant pressure is done at a constant temperature C) Are horizontal because change of state of a refrigerant at constant pressure results in a constantly changing temperature D) Are vertical because change of state of a refrigerant at constant pressure results in a constantly changing temperature ---------CORRECT ANSWER--------------- --A) Are horizontal because change of state of a refrigerant at constant pressure is done at a constant temperature The boundary line between the subcooled liquid region and the saturated mixture region? (pg. 2-10) A) Is 100% saturated liquid B) Is 100% saturated vapor C) Represents a theoretical condition not achievable in a real system D) Represents the critical pressure of the refrigerant ---------CORRECT ANSWER----- ------------A) Is 100% saturated liquid The boundary line that separates the saturated mixture region and the superheated vapor region? (pg. 2-10) A) Is 100% saturated liquid B) Is 100% saturated vapor
C) Represents a theoretical condition not achievable in a real system D) Represents the critical pressure of the refrigerant ---------CORRECT ANSWER----- ------------B) Is 100% saturated vapor A simple refrigeration cycle plotted on the enthalpy diagram illustrates why a condenser must reject more heat than just the heat absorbed in the evaporator because of? (pg. 2-17) A) Subcooling B) Heat of Compression C) Saturation D) Evaporation ---------CORRECT ANSWER-----------------B) Heat of Compression A vertical change (change of pressure) in the subcooled liquid region or in the saturated mixture region __________ the enthalpy of the refrigerant at that point? (pg. 2-11) A) Increases B) Decreases C) Does Not Change D) Multiplies ---------CORRECT ANSWER-----------------C) Does Not Change Superheat enters the system at? A) The condenser, high-pressure receiver, and the evaporator B) The liquid line, evaporator, and condenser
