Ch. 10 Flashcards
- A refrigerant may be defined as a:
a. A liquid that absorbs heat at high pressure and gives up heat at low pressure.
b. A fluid that absorbs heat at a low temperature & pressure and gives up heat by condensing at a higher temperature & pressure.
c. A fluid that absorbs heat at a high pressure.
d. Medium for creating heat.
e. A fluid that absorbs heat at a high temperature & pressure and gives up heat by condensing at a lower temperature & pressure.
b. A fluid that absorbs heat at a low temperature & pressure and gives up heat by condensing at a higher temperature & pressure.
- A good refrigerant should require a _________________.
a. low latent heat value
b. high temperature boiling point
c. high condensing temperature
d. high condensing pressure
e. large amount of heat to evaporate
e. large amount of heat to evaporate
- Ammonia refrigerant will ___________________________.
a. mix easily with mineral oils
b. not mix with mineral oils
c. mix with oils when heated
d. not mix with water
e. be added with oil for lubrication purposes
b. not mix with mineral oils
- A good refrigerant should have _____________________.
a. a high net refrigeration effect
b. a low net refrigeration effect to save power
c. a medium refrigeration effect
d. a high condensing pressure
e. a condensing temperature
a. a high net refrigeration effect
- Group 3 refrigerants are __________________________.
a. extremely flammable
b. moderately flammable
c. non flammable
d. moderately explosive
e. non explosive
a. extremely flammable
- Group 1 refrigerants ______________________________.
a. are quite poisonous
b. are easily ignited
c. have the highest latent heat value
d. are considered the safest
e. are moderately toxic
d. are considered the safest
- NH3 (R-717) refrigerant ___________________________.
a. will not cause corrosion to metals
b. is non-toxic
c. is corrosive in the presence of water to nonferrous metals
d. is very expensive
e. is extremely explosive
c. is corrosive in the presence of water to nonferrous metals
- R-12 and R-22 refrigerants are ____________________.
a. known as halocarbons or Freons
b. used only in commercial establishments
c. extremely toxic
d. used only in indirect systems
e. extremely explosive
a. known as halocarbons or Freons
- The heat necessary to evaporate a liquid refrigerant in mechanical refrigeration is _______________________.
a. sensible heat
b. refrigeration super heat
c. latent heat
d. heat of condensation
e. superheat
c. latent heat
- In a mechanical vapor compression system the compressor’s function is to _______________________.
a. condense the high pressure gas
b. establish two pressure levels
c. reduce the temperature of the refrigerant gas
d. control the flow of refrigerant to the evaporator
e. to compress the vapour, so that heat can be easily removed
b. establish two pressure levels
- Most modern refrigeration systems make use of the principle of absorbing heat by ______________________.
a. condensing refrigerant at a low pressure
b. high evaporating pressures
c. the evaporation of a liquid, and then discarding the heat to the atmosphere
d. evaporation of brine
e. high condensing temperature & pressure
c. the evaporation of a liquid, and then discarding the heat to the atmosphere
- The flow of refrigerant to the evaporator is controlled by the ______________________________.
a. king valve
b. suction flow regulating valve
c. purge valve
d. expansion valve
e. discharge flow regulating valve
d. expansion valve
- The discharge pressure on centrifugal compressors is increased by ____________________________.
a. running the stages in parallel
b. arranging the stages in series
c. slowing up the compressor
d. throttling the nozzles
e. throttling the suction valve
b. arranging the stages in series
- The high and low sides of a refrigerating system are separated by an imaginary line _____________________.
a. from the king valve to the compressor discharge valve
b. between the compressor discharge and suction valves to the brine valve
c. between the compressor discharge and suction valves to the expansion valve
d. From the equalizing valve to the expansion valve
e. between the compressor discharge and suction valves to the king valve
c. between the compressor discharge and suction valves to the expansion valve
- The function of the condenser in a refrigeration compression system is ____________________.
a. to evaporate the liquid to a high pressure gas
b. to establish a pressure differential
c. to cool the hot compressed refrigerant vapor until it condenses to a liquid
d. to condense or liquefy the purge gases
e. to cool the hot compressed liquid refrigerant in the receiver
c. to cool the hot compressed refrigerant vapor until it condenses to a liquid
- The purpose of the expansion valve is to ____________.
a. isolate the high and low sides of the system
b. regulate the flow of refrigerant to the evaporator
c. expand the refrigerant gas for better refrigeration effect and higher temperatures
d. control the brine flow
e. control the temperature of the refrigerant
b. regulate the flow of refrigerant to the evaporator
- Some reciprocating compressors on ammonia systems are protected from liquid slugs by _________________.
a. spring loaded safety heads
b. automatic drain traps
c. extra heavy valves
d. low pressure cut outs
e. high water cut outs
a. spring loaded safety heads
- The evaporator is where _________________________.
a. the liquid refrigerant is stored
b. the liquid refrigerant absorbs heat and boils into a vapor
c. the gas condenses
d. most of refrigerant is stored
e. the refrigerant is charged into liquid
b. the liquid refrigerant absorbs heat and boils into a vapor
- The liquid receiver is a/an ________________________.
a. oil storage unit
b. storage for most of the brine
c. contaminated liquid storage tank
d. vessel to charge the system with oil
e. pressure vessel
e. pressure vessel
- Brine used in ammonia indirect systems is usually ____________.
a. lithium bromide
b. calcium chloride
c. sodium chloride
d. sodium hydroxide
e. calcium hydroxide
b. calcium chloride
- In an indirect ammonia system using brine ______________.
a. the refrigerant is cooled by the brine
b. the brine is used to condense the ammonia
c. the brine absorbs heat from the space to be cooled
d. only Freon 22 refrigerants are used
e. the condenser pressure must be very high
c. the brine absorbs heat from the space to be cooled
- Absorption systems compared to compression require _________________.
a. more items of equipment
b. less items of equipment
c. approximately the same amount of equipment
d. less space
e. more electrical power to run
a. more items of equipment
- Absorption type refrigeration systems require ____________.
a. condenser, receiver, compressor & expansion valve
b. reciprocating compressors
c. pumps and compressors
d. centrifugal compressors
e. more space than compression systems
e. more space than compression systems
- The direct refrigeration system is one in which the evaporator is in direct contact with _____________.
a. the cooling water in the condenser
b. the material being refrigerated
c. the calcium chloride in the cooling coil
d. the brine in the brine tank
e. the cooling water on the suction side of the compressor
b. the material being refrigerated
- Solution of calcium chloride used in an indirect refrigeration system can be subjected to temperatures as low as _____________.
a. -11°C
b. -18°C
c. -25°C
d. -51°C
e. -4°C
d. -51°C
- The evaporator in a centrifugal compressor (chiller unit) system is also called a ________________.
a. vaporizer
b. eliminator
c. purger
d. cooler
e. vent condenser
d. cooler
- A two stage, duplex compressor refrigeration system is used where _______________.
a. moderate low temperatures are desired
b. extremely low temperatures are desired
c. small quantities of refrigerant are required
d. high quantities of refrigerant are required
e. the cost of refrigerant is high
b. extremely low temperatures are desired
- A duplex compression refrigeration system is used when temperatures below ____ °C are required.
a. -18
b. -20
c. -45
d. -51
e. -92
e. -92
- In a two stage, duplex compressor refrigeration system, the condenser for the first stage is the ______________ for the second stage.
a. eliminator
b. purger
c. receiver
d. evaporator
e. liquid cooler
d. evaporator
- In a two stage refrigeration system, the 1st stage compressor is usually a ____________ compressor.
a. centrifugal
b. axial flow
c. diffuser
d. rotary
e. reciprocating
d. rotary
- In a two stage refrigeration system, the 1st stage compressor is also known as a ___________ compressor.
a. booster
b. standby
c. low volume
d. extraction
e. refrigerant
a. booster
- In a two stage refrigeration system, the 2nd stage compressor is usually a ____________ compressor.
a. centrifugal
b. axial flow
c. diffuser
d. rotary
e. reciprocating
e. reciprocating
- Because of the greater range between the suction and discharge pressures of a multi-stage refrigeration system, the necessary compression is usually divided between ____ single-stage compressors.
a. 2
b. 3
c. 4
d. 5
e. 6
a. 2
- There are ____ basic elements common to most compression refrigeration systems.
a. 2
b. 3
c. 4
d. 5
e. 6
d. 5
- A/An _____________ is usually provided between the low pressure discharge and high-pressure suction of a multi-stage refrigeration system.
a. condenser
b. receiver
c. purger
d. evaporator
e. intercooler
e. intercooler
- The separation of the solution of ammonia and water in the ammonia absorption system is done by means of ___________.
a. heat
b. sprayers
c. gravity
d. rectification
e. centrifuge
a. heat
- At about 240 kpa, the ammonia will boil at a temperature of about _____ °C.
a. -10
b. -15
c. -20
d. -25
e. -30
b. -15
