Download Reta Caro Exam Practice Test 2025| Answered 100% Correctly and more Exams Electronics in PDF only on Docsity!
Reta Caro Exam Practice Test 2025|
Answered 100% Correctly
Conduction is defined as heat energy that is moving through a solid substance What is the primary purpose of a refrigeration system? achieve and maintain a temperature What is a hazard of trapping liquid? A possible release How much can the pressure of trapped liquid increase per degree Fahrenheit of temperature increase 100 to 150 psi Mechanical refrigeration is a series of steps that moves heat energy from a space or object to an area where it can do no harm How does the refrigeration compressor maintain the temperature in the system evaporators?
Drawing out vaporized refrigerant at a rate to maintain the desired evaporating pressure Which natural refrigerant is considered to be non- flammable Carbon Dioxide Heat energy always flows from an object at a higher temperature to an object at a lower temperature 32 psia equals 17.3 psig 0 ° F is equal to
- 18 ° C Why does the refrigerant in the condenser change state from vapor to liquid The refrigerant loses heat energy to the surrounding environment If a liquid is below its saturation temperature what is its condition? Subcooled What are the four necessary components of a mechanical refrigeration system? expansion device , evaporator , compressor , condenser
When suction pressure rises , the operator should start another compressor The crankcase oil heater should be ON when the compressor is off. Slugging is caused by oil or liquid refrigerant What should be done if liquid refrigerant appears while draining oil? Do what the SOP states Proper oil management for a refrigeration system requires that a log should record all oil added to and removed from a system When heat is added to saturated liquid refrigerant it will always evaporate What effect does the addition of fins to evaporator coils have? It increases the efficiency of a unit by increasing the surface area During hot gas defrost high pressure gas flows through and condenses in the evaporator
Evaporative condensers derive their heat rejection capability from the evaporation of water Air cooled condensers usually have higher head pressures than evaporative condensers What are the two types high pressure receivers based on how liquid flows into them? Surge and through type It is good practice to only fill a vessel how full with liquid? 80 % Bottling is defined as refrigerant held in the condenser due to the pressure difference at the outlet of the condenser caused by active and inactive condenser circuits What is a non condensable gas in a refrigeration system? A gas that cannot be condensed at the temperatures and pressures in the system In refrigeration , what does purging refer to? Removing non condensables from the system
Which of the following expansion devices would not normally be used as a part of a small refrigeration system? Hand expansion valve Gravity feed flooded evaporators provide the maximum heat transfer for given evaporator size. The pumped recirculated type evaporator does not have to be close to the vessel that feeds it liquid Which of the following secondary cooling devices operates as a thermal storage device? Ice builder Plate freezers achieve fast freezing because of close package contact with the plates and close refrigerant contact with the plates Oil coolers are used on screw compressors because screw compressor oil absorbs much of the heat of compression from the refrigerant How many stages or steps are used in most screw compressor oil separators? 4
Care must be taken when handling and storing oil containers that have been opened because? containers should be resealed as oil will moisture from the atmosphere What is a sign that liquid slugging is occurring and should be immediately addressed? Rapid discharge temperature drop Which of the following is a danger of slugging in a compressor? Mechanical damage to the compressor and refrigerant loss When coming on duty the operator should acquaint themselves with all current operating conditions How can an operator get thoroughly acquainted with an unfamiliar refrigeration plant? They can study the P & IDs and confirming against the actual system Why do rotary vane compressors have very little starting load? The blades only seal when the compressor is up to speed
either a sulfur stick on ammonia or electronic leak detector for CFCs or HCFCs Under the Clean Air Act and the Montreal Protocol as long as a technician does not perform work on portions of a system containing refrigerant there is no requirement for certified Which refrigerant was the first to be phased out by Montreal Protocol? CFC 12 What is one advantage to having evaporator pressures higher than atmospheric pressure? Higher pressures keep air out of the system Calculate the compression ratio for an HCFC system with the following conditions : Saturated suction pressure 20 psig Saturated discharge pressure 175 psig Motor amps are 154 5.47 : 1 Superheated refrigerant can only be a vapor
At a constant pressure , the latent heat of condensation of a substance is the same as the latent heat of vaporization of the substance Flash gas is defined as the vapor created at the expansion device A meat plant processes 100 animals a day with an average processed weight of 750 pounds of beef per animal. The meat must be cooled from 85 ° F to 45 F. The specific heat of sirloin steak is 0.735 BTU / lb. / ° F. How many BTUs must be removed? 2,205,000 BTU What is the condition of a boiling liquid? Saturated If specific heat for air is .24 BTU / lb. / ° F and the specific volume is 12.7 cu. ft./lb , How much heat energy must be removed to cool from 70 ° F to 40 ° F , the air in a room that is 16'x 12 ' x 8 '? 870.8 BTU
Variable Vi is added to a screw compressor to match actual conditions to minimize over / under compressing the discharge gas Two - stage refrigeration systems use compressors that are working in series with one another instead of parallel compressors working on a common suction and discharge line Which of the following is NOT an issue when oil goes out into the system beyond the compressors , and past the oil separator? Improved actuation of the automatic valves Moisture contained in the air may deposit on the surface of the evaporator forming frost , decreasing the efficiency of the coil Where do non condensable gases accumulate They accumulate in the system high side Saturated liquid ammonia at 70 ° F weighs 38.04 lbs./cu. ft.
An ammonia compressor is operating with - 30 ° F suction temperature and a suction pressure of 8.7 inches of vacuum. What is the condition of the suction vapor? 10 ° F superheated What is the published upper explosive limit for ammonia? 25 % What is needed to get a fluid to flow? A pressure difference A conventional mechanical refrigeration system is considered a closed loop system On a DX system , what does the expansion valve control? The flow of liquid into the evaporator Which of the answers below is an example of heat transfer by conduction? A rod heated on one end becoming warm at the other end If the force acting on an area of 5 square inches is 150 lb. , what is the pressure on the area?
