Review Quiz Flashcards by Kyle Halverson

An automatic expansion valve uses a thermal sensing bulb to help control the amount of refrigerant being fed to the evaporator

TRUE OR FALSE

False

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A refrigeration system that continuously runs under high-load conditions (hot pull downs) would most likely use a thermostatic expansion valve with a vapour charged thermal bulb assembly

TRUE OR FALSE

True

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The higher the rpm of a compressor, the higher the pumping efficiency

TRUE OR FALSE

False

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The rotary screw compressor uses an open motor instead of the hermetic design

TRUE OR FALSE

True

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Hard starting may also occur in a low ambient condition causing low head pressures

TRUE OR FALSE

True

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When the evaporative condenser is used in colder climates, freeze protection must be provided in winter

TRUE OR FALSE

True

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The film factor is a relationship between the medium giving up heat and the heat exchange surface

TRUE OR FALSE

True

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A limited amount of flash gas created in the liquid line increases a systems efficiency

TRUE OR FALSE

False

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Some thermostatic expansion valves are equipped with built-in check valves to prevent refrigerant from flowing backward through the TXV

TRUE OR FALSE

True

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The higher the temperature in a low-side float system, the higher the low-side pressure

TRUE OR FALSE

True

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If the orifice of a valve assembly is oversized, the valve will hunt or surge

TRUE OR FALSE

True

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A liquid cross charged sensing bulb may use a mixture of different refrigerants to achieve the desired operating characteristics

TRUE OR FALSE

True

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A liquid cross-charged sensing bulb uses a refrigerant that is the same as the one in the system

TRUE OR FALSE

False

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TXV’s may be used on multiple-evaporator systems

TRUE OR FALSE

True

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In an open-drive compressor, the motor is often cooled by passing refrigerant and oil over the windings

TRUE OR FALSE

False

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In a pressure lubrication system, the crank throw dips into the oil at each crankshaft revolution

TRUE OR FALSE

False

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On external drive compressors, the crankshaft seal rubbing surfaces should be lubricated.

TRUE OR FALSE

True

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All hermetic compressors require a crankshaft seal.

TRUE OR FALSE

False

Poppet valves are suitable only for low-speed compressors.

TRUE OR FALSE

True

The pressure limiting TXV ____.

a) allows the compressor to operate at low condenser entering air temperatures
b) shuts off the condenser fan during hot pull down
c) maintains the full refrigerant flow rate during a hot pull down
d) limits the refrigerant flow rate to the compressor capacity

d) limits the refrigerant flow rate to the compressor capacity

When the load on the evaporator increases, the TXV ____.

a) increases the flow of refrigerant
b) decreases the flow of refrigerant
c) maintains constant head pressure
d) decreases the pressure drop across the evaporator

a) increases the flow of refrigerant

Rotary compressors are used primarily in ____.

a) large industrial refrigeration and air conditioning systems
b) residential air conditioning
c) small commercial refrigeration units
d) high volume residential refrigeration

b) residential air-conditioning

If the compression ratio of a system with a reciprocating compressor decreases, the amount of refrigerant pumped by the compressor ____.

a) will increase
b) will decrease
c) will remain the same
d) cannot be determined

a) will increase

If an R-12 refrigeration system has its air-cooled condensing unit on a 100°F roof and the condenser outlet temperature (refrigerant) is 115°F, with how much subcooling is the condenser operating?

a) 30°F
b) 15°F
c) 100°F
d) 130°F

b) 15F

In a water-cooled condenser, a regulating valve is used to control the ____. refrigerant flow through the pressure reducing device refrigerant condensing temperature suction pressure water temperature

b) refrigerant condensing temperature

If an evaporator has a pressure drop of 10 psig and the low side pressure is 15 psig, what is the pressure at the inlet of the evaporator? 5 psig 10 psig 15 psig 25 psig

d) 25psig

The ____ of the liquid refrigerant determines the coil operating temperature. freezing point melting point transition temperature boiling temperature

d) boiling temperature

The superheating done by a suction line-liquid line heat exchanger helps prevent ____. liquid slugging in the compressor frozen drain pans frosted evaporators tripped thermal overloads

a) liquid slugging in the compressor

A hot-water reclaim tank is a cylinder filled with water that absorbs heat from refrigerant flowing through a refrigeration system’s ____. discharge line suction line accumulator sight glass

a) discharge line

A condenser that consists of an inner tube through which water flows in one direction and a surrounding outer tube through which refrigerant flows in the opposite direction of the water flow is a ____. shell-and-tube shell-and-coil tube-within-a-tube All of the above.

c) tube-within-a-tube

Since a compressor continues to operate after a pump-down solenoid closes, ____. refrigerant from the evaporator and low side is pumped down refrigerant collects in the evaporator and accumulator high-side pressure drops a high-pressure control is used to turn off the compressor

a) refrigerant from the evaporator and low side is pump down

Heat exchangers featuring metal fins of various styles and types connected to evaporator tubing are ____ evaporators. baffle-tube fin-and-tube plate shell-and-sheet

b) fin-and-tube

Heat exchangers made from two metal sheets that are welded together to form a series of passages are ____ evaporators. baffle-tube fin-and-tube plate shell-and-sheet

c) plate

The function of EEVs is to maintain ____ at a desired setting. superheat subcooling ambient temperature head pressure

a) superheat

To maintain a constant pressure in the evaporator when the system is running, an AXV ____ refrigerant flow when the evaporator pressure drops. decreases stabilizes increases None of the above.

c) increases

When used with thermostatic expansion valves, the term superheat refers to the difference in temperature between the evaporator inlet and the ____. liquid line sensing bulb discharge line ambient air

b) sensing bulb

Metering devices that can change their orifice size to account for changes in cooling loads are referred to as ____ metering devices. modulating flow fixed limited

a) modulating

An oil control device that regulates the level of oil within a compressor using a float mechanism is an ____. oil changer oil level regulator oil level separator oil collector tank

b) oil level regulator

The compressor protection device that is specifically intended to protect a compressor from overcurrent is a(n) ____. fuse and circuit breaker thermal overload device crankcase pressure regulator (CPR) accumulator

a) fuse and circuit breaker

A ____ compressor compresses vapor between a matched set of helical rotors. screw scroll centrifugal rotary

a) screw

Which of the following statements regarding poppet valves is false? Poppet valves are very sturdy. Poppet valves are typically found in large compressors. Poppet valves are closed by spring pressure. Poppet valves operate more quickly than reed valves.

d) poppet valves operate more quickly than reed valves

Which of the following statements regarding piston rings is false? A compression ring prevents pressurized refrigerant from blowing past the piston into the crankcase. The inner diameter of a piston ring is slightly larger than the piston diameter. The ends of piston rings are beveled to allow overlap. An oil ring prevents excess oil from entering the cylinder.

b) the inner diameter of a piston ring is slightly larger than the piston diameter

A crankshaft that is cast with offset journals is called a(n) _____ crankshaft. integrated reciprocal-type crank throw–type None of the above.

c) crank throw-type

Which type of compressor is most similar in construction to an automobile engine? Rotary. Reciprocating. Centrifugal. Screw.

b) reciprocating