Ref Flashcards
In an ammonia system the oil gage must be kept:
A. Closed except when checking oil level
B. Open at all times
C. Closed when machine is shut down
D. Open when machine is shut down
A
How is ammonia system purged so that operator will not be overcome by the fumes?
A. Into a bucket of lube oil
B. Back into the compressor
C. Into a bucket of water
D. Into the atmospheric line
C
Which of the following could be used to check a leak in an ammonia system?
A. Litmus paper
B. Halide torch
C. Sulfur stick
D. A and C
D
The crossover connection in an ammonia system can be used to
A. hot- gas defrost
B. Pump air out of the system
C. Add refrigerant to the system
D. Reduce the pressure on the discharge side of the condenser
A
Ammonia leaks in the condenser can be detected by:
A. Smelling the discharge water
B. Applying litmus paper to the circulating water discharge
C. Adding oil of peppermint to the system and tracing the smell
D. Applying a soapy solution to the condenser heads and bubbles looking for
B
Valves and piping in an ammonia system are made of:
A. brass
B. bronze
C. iron
D. copper
C
When purging an ammonia condenser into a bucket of water, one can tell when the air is out and
ammonia starts to come through by the:
A. Smell of ammonia being liberated from the water
B. Color of the water turning green
C. Color of the water turning bluish
D. Change of bubbling sound of air to the cracking sound of ammonia
D
A sulfur stick burning in the presence of ammonia give off a:
A. Dense yellow smoke
B. Dense red smoke
C. Dense white smoke
D. Dense green smoke
C
An ammonia leak will turn litmus paper
A. blue
B. green
C. red
D. yellow
A
The purpose of the receiver is to:
A. Cool the refrigerant gas
B. Separate the oil from the refrigerant
C. Store the refrigerant
D. Condense the refrigerant
C
When securing a Freon system for repairs:
A. Pump down to 1 or 2 pounds pressure
B. Pump down to a slight vacuum
C. Pump down to 10 or 15 pounds pressure
D. Remove all refrigerant from the system
A
When charging Freon system, all the valves should be in their normal position except the:
A. Solenoid valve
B. Purge valve
C. King (liquid) valve
D. Expansion valve
C
Before securing a compressor to do maintenance work on it, be sure to:
A. Have gas mask handy
B. Make arrangements to have perishables taken care of
C. Notify the engineer
D. A and B
D
The function of the expansion valve is to:
A. Regulate the amount of liquid refrigerant to the expansion coils
B. Change the gas refrigerant to a liquid
C. shut off the flow of the flow of refrigerant to the condenser
D. Change the high-pressure liquid to a low-pressure liquid
A
When heavy electrical currents are involved, the thermostat will be operated by a:
A. Pressure pipe
B. fusetron
C. relay
D. Small circuit breaker
C
Water in the refrigerant is liable to:
A. Freeze on the expansion valve seat and cut the flow of refrigerant
B. Clog the oil trap
C. Freeze in the king (liquid) valve
D. Emulsify the oil in the compressor
A
Air can be prevented from getting into the system by:
A. Running the refrigerant through an aerator
B. Keeping the dehydrator clean at all times
C. Keeping all glands and stuffing boxes on the high-pressure side tight.
D. Keeping all glands and stuffing boxes on the low pressure side tight
D
Which of the following would not cause high suction pressure?
A. Suction valve not adjusted properly
B. Expansion valve stuck open
C. Leaky suction valves
D. Insufficient refrigeration
D
The purpose of the expansion valve is to control the flow of the refrigerant to the evaporator, the other
function is to
A. Reduce the pressure of the liquid refrigerant
B. Increase the pressure of the vapor refrigerant
C. Reduce the pressure of the vapor refrigerant
D. Increase the pressure of the liquid refrigerant
A
What is the device used to protect the compressor from overloading due to high head pressure
A. Overload relay
B. Hold back suction valve
C. Thermostatic expansion valve
D. Expansion valve
A
Which of the following measures the density of salt in water
A. Salimeter
B. Hydrometer
C. Pitot tube
D. Calorimeter
A
The agent used in an indirect reefer system is:
A. Calcium chloride
B. Potassium chloride
C. Sodium chloride
D. A or C
D
If the freezing point of water is 0° C, which of the following is its melting point
A. Slightly less than 0° C
B. Slightly more than 0° C
C.0 C
D. 32° C
C
A salimeter reads the
A. Density of brine
B. Rate of brine
C. Dew point temperature
D. Relative humidity
A
It prevents the refrigerant from the condenser to go back to the compressor
A. Check valve
B. Float switch
C. Expansion valve
D. Low side float
A
R-22 is
A. Dichlorodifluoromethane
B. Monochlorodifluoromethane
C. Methyl chloride
D. Trichlorodifluoromethane
B
Tons of refrigeration in Btu/24 hours is
A. 288,000
Β. 28,800
C. 290,000
D. 29,000
A
If PV is the power for a vapor- compression refrigeration system, then what is the power required for an
air- refrigeration system, assuming that they have the same capacity
A. 5PV
B. 2PV
C. PV/10
D. 1/PV
A
The amount of sensible heat for a sensible heat ratio of 0.80 and a total cooling load of 100 is
A. 80
B. 20
C. 100
D. 60
A
The effect of superheating refrigerant is to the
A. Increase the COP
B. Increase and decrease the COP
C. Decrease the COP
D. Maintains the COP
A
The high pressure of refrigeration system consist of the line to the expansion valve, the receiver, the
uppermost half of the compressor and the
A. Line after the expansion valve
B. Lower most half of the compressor
C. Condenser
D. Evaporator
C
Which of the following materials is suitable for tubing in refrigeration application where refrigerant
ammonia is employed
A. Plastic
B. Brass
C. Steel
D. Copper
C
The boiling point of freon 22 is
A.-41.40 F
B. 40.60° F
C. -38.40° F
D.-31.40° F
A
The ice making capacity is always
A. Directly proportional to the refrigerating effect
B. Less than the refrigerating effect
C. Greater than the refrigerating effect
D. Equal to the refrigerating effect
A
The highest temperature in a vapor compression cycle is produced during
A. Receiver
B. Evaporator
C. Condenser discharge
D. Compressor discharge
D
The secondary refrigerant used in milk chilling plants is generally
A. Brine
B. Ammonia
C. Glycol
D. Sodium silicate
C
The sensible ratio is 0.8, that is
A. 20% latent heat and 60% sensible heat
B. 80% sensible heat and 20% latent heat
C. 80% sensible heat and 20% sensible and latent heat
D. 20% latent heat and 80% sensible and latent heat
B
An odorless refrigerant whose boiling point varies over a wide range temperature
A. Freon 22
B. Freon 12
C. Ammonia
D. Freon 11
A
A refrigeration system in which only part of the refrigerant passes over the heat transfer surface is
evaporated and the balance is separated from the vapor and recirculated.
A. Direct expansion system
B. Chilled water system
C. Flooded system
D. Multiple system
C
The part that directs the flow of refrigerant through the compressor
A. Wrist pin
B. Valve
C. Piston
B
Lithium bromide is used in refrigeration system in:
A. Condensate return lines
B. Absorbers
C. Centrifugal compressors
D. lon exchangers
B
Select the one in which secondary refrigerant is used
A. Domestic refrigerator
B. Room air conditioner
C. Deep freezer
D. Ice plant
D
A device whose primary function is to meter the flow of refrigerant to the evaporator
A. Sniffer valve
B. Equalizer
C. Thermostatic expansion valve
D. Crossover valve
C
In a refrigerating system, the heat absorbed in the evaporator per kg mass of refrigerant passing
through:
A. Equals the decrease in enthalpy
B. Does not depend on the refrigerant used
C. Is decreased if pre-cooler is used
D. Equals the increase in volume
A
Ton of refrigeration is a unit equivalent to
A. 50.4 kCal/sec
B. 12660 kN-m/hr
C. 3413 kW-hr
D. 2545 Btu/hr
B
The main purpose of a subcooler in a refrigerating system especially a two-stage
system is to:
A. Increase the heat rejection per ton and avoid system shutdown
B. Improve the flow of the evaporator gas per ton and increase the temperature
C. Reduce the total power requirements and return oil to the compressor
D. Reduce the total power requirements and heat rejection to the second stage
D
The vapor cycle in thermal efficiency as the refrigeration cycle is to the?
A. Energy efficiency ratio
B. COP for a refrigerator
C. COP for a heat pump
D. Carnot efficiency
B
A freon-12 refrigeration system is filled with thermal expansion valves. The valves are rated in:
A. Pound per minute
B. Superheat setting
C. Tons of refrigeration
D. Cubic feet per minute
C
Soft copper tubing that is used for refrigerant piping, erected on premises containing other than group 1
refrigerant must be protected by?
A. Supporting it by approved clamps
B. Limiting its length between its supports up to 10 ft.
C. A rigid or flexible metal enclosure
D. Wrapping it with insulation tape throughout its length
C
Boiling temperature of Freon 22 is;
A. -33.33° F
B. -78.5° C
C. -29.8° C
D. -41.04 F
D
