PIPE Elements 10

The component that absorbs heat into the refrigerant is the
a. metering device
b. condenser
c. compressor
d. evaporation

A high load affects the operation of a constant pressure expansion valve by
a. causing overload
b. requiring an external equalizer
c. starving the evaporator
d. all if the above

The high side of the system includes
a. metering devices
b. an evaporator
c. a suction line
d. a receiver

Of the following

Superheat is heat added
a. with the aid of the automatic expansion valve
b. after all liquid has been changed to vapor
c. for the vaporization of the evaporator
d. to increase the heat of a substance

An expansion valve is built most nearly like
a. a shut-off valve
b. a pressure-reducing valve
c. a blow-off valve
d. a diuble-seated globe valve

The low side of the system includes
a. a receiver
b. a compressor
c. a discharge
d. an evaporator

What causes the drop in temperature and pressure as liquid refrigerant passes through the expansion valve
a. the superheat of the refrigerant
b. the change in the rate of flow of the refrigerant
c. the partial evaporation of refrigerant as it passes through the valve
d. the temperature and pressure of the refrigerant in the liquid line

The heat used to change a liquid to a gas or vapor is called latent heat of
a. vaporization
b. fusion
c. condensation
d. superheat

The subcooling effect of a liquid refrigerant just before the expansion valve would result in
a. increased refrigerant effect
b. increased refrigerant density
c. increased miscibility of the oil
d. none of the above

A thermometer is said to detect
a. heat of vaporization
b. sensible heat
c. potential energy
d. hidden heat

The automatic expansion vakve maintains constant pressure at
a. the condenser inlet
b. the evaporator inlet
c. the liquid line
d. the condenser outlet

Hidden heat in refrigeration work is called
a. superheat
b. kinetic heat
c. sensible heat
d. latent heat

Which if the following is also referred to as a backward opersting valve?
a. thermal expansion valve
b. hand expansion valve
c. low side float
d. automatic expansion valve

What is another word for latent heat?
a. hidden heat
b. absolute heat
c. sensible heat
f. specific heat

What controls the operation of a high-side float?
a. accumulator
b. evaporator
c. condenser and receiver
d. evaporator and condenser

Heat added to a gas above the saturation temperature is called
a. specific heat
b. potential energy
c. superheat
d. all of the above

In a high-side float

The latent heat used to change a liquid to a gas or vapor is called the latent heat of
a. condensation
b. fusion
c. evaporization
d. temperature

On a refrigeration system with a high-side float metering device

Convection is the process by which
a. heat moves through gases and liquids
b. transfer of heat occurs by direct contact
c. heat gives up to the surrounding air
d. heat changes state

In a flooded evaporator using an accumulator and float valve

Conduction is the transfer of
a. heat by means of movement
b. heat by direct contact between two objects
c. heat by means of radiation of the sum
d. molecules in motion around a substance

A flooded system with a low-side float uses a thermostat

Saturated vapor is
a. heat that can be sensed
b. the number of Btu required to change the state of an object
c. a substance that has just turned into a vapor
d. all of the above

One advantage of a low-side float system is that it
a. requires a large amount of refrigerant
b. can be used with a water cooled condenser
c. eliminates flash gas in the evaporator
d. can be used with a low starting torque motor

The evaporator absorbs heat from the air or brine because the liquid refrigerant entering the evaporator
a. has a lower temperature than the air or brine
b. has a higher temperature than the air or brine
c. boils to a low-pressure gas
d. bouls to high-pressure gas

One disadvantage of a low-side float system is that it
a. is nonadjustable
b. requires a large amount of refeigerant
c. is very expensive
d. cannot be used on multiple systems

The evaporator
a. removes heat from the refrigerant
b. absorbs heat into the refrigerant
c. stores heat into the refrigerant
d. keeps the compressor busy

In a flooded system

As the load on an evaporator decreases
a. the discharge pressure increases
b. the oil pressure increases
c. the suction pressure increases
d. the suction pressure decreases

Flash gas forms in the
a. compressor
b. condenser
c. evaporator
d. heat exchanger

The heat picked up in the evaporator must equal
a. the heat gained by the condenser
b. the heat lost by the condenser
c. the heat of compression
d. the heat lost by the medium being cooled

The flash gas loss at the expansion valve is approximately
a. 2%
b. 5%
c. 22%
d. 12%

The disadvantage of a flooded system is
a. it cannot be used on multiple systems
b. it needs a large charge of refrigerant
c. it cannot be used with a low-pressure motor control
d. it can be used only with ammonia

What does a high superheat mean?
a. flooded evaporator
b. starved evaporator
c. pressure evaporator
d. motor speed too high

Flooded feeds are diferent from direct expansion feeds because they
a. allow for regurgitation of liquid refrigerant
b. use bigger and better evaporators for this purpose
c. are not as effective in operation
d. allow for recirculation of liquid refrigerant

What does a low superheat indicate?
a. flooded evaporator
b. starved evaporator
c. pressure evaporator
d. motor speed too low

The suction pressure of any refrigerant system is adjusted
a. to a corresponding evaporator temperature below the material being cooled
b. to a corresponding evaporator temperature equal to the material being cooled
c. to a pressure above atmospheric at all times
d. none of the above

Which of the following distributors are not used with an external equalizer thermostatic expansion valve
a. manifold type
b. venturi type
c. centrifugal type
d. pressure-drop type

A direct expansion evaporator has frost on the upper and lower coils.
This indicates
a. the evaporator is flooded
b. the evaporator is starved
c. the evaporator is short of refrigerant
d. there is coil logging in the evaporator

Thermal expansion valves are generally at stated suction temperature in
a. tons of refrigeration effect
b. pounds per minute of refrigerant pumped
c. pounds per hour of refrigerant pumped
d. cubic feet per minute of refrigerant pumped

When the evaporator load increases

On an operating electric expansion valve

Baffles in a gravity coil evaporator are used
a. for condensation
b. for proper air flow
c. to prevent moisture carry-over
d. all of the above

The purpose of a condenser is to
a. remove water from the refrigeration system
b. add heat to the refrigeration system
c. remove heat from the refrigeration
d. store liquid refrigeration

The temperature of the medium being cooled must be
a. below the freezing point of the area to be cooled
b. above the evaporator temperature
c. equal to the evaporator temperature
d. below the evaporator temperature

An atmospheric condenser is generally
a. on the floor under the roof
b. in the refrigeration room
c. on the roof
d. none of the above

Assuming all other conditions are constant
a. as low-side pressure falls

A condenser is
a. a good cost-saving accessory to a refrigeration system
b. the exit for heat in a refrigeration system
c. always mounted above the compressor
d. always mounted below the compressor

The two basic types of evaporators are
a. prime surface and finned
b. finned and plate
c. direct expansion feed and plate
d. flooded and direct expansion feed

If a refrigerating system does not react to an adjustment of the TXV

A decrease in load on an evaporator cause
a. more refrigerant to be required
b. pressure drop in the evaporator
c. increase in evaporator capacity
d. more heat to be absorbed

In a compression refrigeration system

closes
d. first closes

closes

Which of the following statement is most nearly correct?
a. The efficiency of an evaporator coil decreases as the frost thickness increases
b. The efficiency of an absorber depends on and varies directly with the compressor speed
c. To lubricate the inside surfaces of an evaporator coil

Thermostatic expansion valves are rated in
a. superheat settings
b. horsepower
c. tons of refrigeration
d. all of the above

Prime surface evaporators operating below 32⁰F must frequently be
a. purged
b. cleared
c. defrosted
d. painted

TXV ratings are based on
a. slightly sub-cooled liquid entering the valve
b. vapor-free bulb of a TXV valve were moved to the valve
c. liquid with a small amount of vapor were moved to the valve
d. 10⁰F sub-cooled liquid entering the valve

Which of the following would not cause a starved evaporator?
a. improper bulb location
b. clogged distributor line
c. shortage of refrigerant
d. metering device stuck in open position

If the feeler bulb of a TVX valve were moved to the
a. more than 10 superheat
b. less than 10 superheat
c. no effect on superheat
d. fluctuating superheat

A Freon-12 refrigerating system in an air conditioning plant is equipped with a finned-tube evaporator. In operation

An external equalizer is used on an evaporator with a pressure drop of
a. less than 2 pounds
b. more than 2 pounds
c. less than 10 pounds
d. more than 10 pounds

The fastest way to remove frost from a direct expansion finned-tube evaporator is
a. shut it down and let the frost melt
b. run a hot gas line to the coil
c. wash frost off with warm water
d. escape frost off

A thermostatic expansion valve with a static setting of 7 superheat would have a field setting of
a. 7 superheat
b. 0 suerheat
c. 4 superheat
d. 11 F superheat

A predetermined amount of refrigerant is used in what type of evaporator?
a. flooded evaporator
b. direct-expansion evaporator
c. indirect-type chiller
d. plate-type evaporator

If the bulb of a TXV is installed right after the expansion valve

The selection of the proper evaporator depends mainly on
a. price
b. size
c. color
d. application

If you open the adjustment of a TVX

What happens in an evaporator?
a. high-pressure liquid converts to low pressure liquid
b. refrigerant in the gas state is saturated
c. low-pressure gas converts to low pressure liquid
d. high-pressure gas converts to low pressure liquid

A thermostatic expansion valve was factory set at 0 superheat. How much was the field setting?
a. 0-3
b. 3-5
c. 4-8
d. 10-15

Is the temperature outside the evaporator higher or lower than the inside temperature?
a. higher
b. stay the same
c. lower
d. 10 dehrees lower

a TEV is attached to a fined evaporator coil with the bulb clamped to the suction line. In normal operation

Secondary refrigerants are usually
a. a zeotrope
b. halocarbons
c. water or brine
d. triflouromethane

A direct expansion cooling coil has a TXV. If the load variations are wide and subject to rapid change

In a refrigerant system

In a refrigeration system

The direct expansion system

A TEV shipped from the factory has static superheat setting of
a. 3 F
b. 5 F
c. 7 F
d. 10 F

The refrigerant leaving a flooded evaporator is
a. just like that leaving a D-X evaporator

The static setting of a TXV is set
a. in the factory
b by the operator
c. in the field
d. all of the above

The flow of refrigerant into a flooded evaporator is controlled so it has
a. mostly liquid refrigerant at the inlet but gas near the outlet
b. all its tubes wetted by liquid refrigerant from beginning to end
c. mostly liquid refrigerant at its outlet but gas at its inlet
d. a mixture of liquid and vapor refrigerant in its tubes from beginning to end

What is the purpose of an external equalizer on a TEV?
a. It lubricates the coil of the TEV
b. It equalizes the pressure in the evaporator
c. to eliminate the effect of the pressure drop across the evaporator
d. none of the above

As flash gas increases

Assume a TXV is set for 10 superheat. This means the gas passing yhe remote bulb is about 10
a. above the temperature of the evaporating refrigerant
b. below the temperature of the evaporating refrigerant
c. above the temperature of the ambient air temperature
d. below the temperature of the ambient air temperature

Superheat is wanted at the outlet of a D-X evaporator mainly to
a. improve evaporator efficiency
b. increase evaporator capacity
c. protect the compressor
d. increase system capacity

In a particular air conditioning system using R-12

An evaporator that fails to provide superheat at its outlet places which compressor is in the most serious danger?
a. rotary
b. centrifugal
c. reciprocating
d. screw

A thermostatic expansion valve in a refrigeration system
a. regulates the pressure in the evaporator
b. regulates the compressor pressure
c. regulates the flow of refrigerant to the pre-cooler
d. modulates and controls the flow of refrigerant to the evaporator

A prime-surface evaporator is one that
a. has prime sprayed on it to protect it
b. is either a plate-surface or plate-finned type
c. is either a bare-tube or plate-surface type
d. none of these

If the external equalizer line of a TXV is disconnected from the evaporator

Scale from water deposits wil build up and need to be removed periodically from
a. the outside and inside of the tubes of a D-X cooler
b. the inside and outside of the tubes of a flooded cooler
c. the inside of a tube-and-shell cooler only
d. the outside of a tube-and-shell cooler only

What is the highest pressure tjat can be exerted on a Freon system's TXV bukb (vapor charge)

What is the difference between flooded and dry-expansion shell and tube evaporators?
a. The flooded cooler has refrigerant in the shell and water in the tubes
b. The dry-expansion evaporator has refrigerant in the tubes and brine in the shell
c. The flooded cooler has refrigerant in the tubes and brine in the shell
d. A or B

When using a TXV in a Freon system eith the temperature range of +40 to -40

The TXV is controlled by
a. coil temperature
b. the difference between gas temperature and the temperature corresponding to the gas pressure
c. the difference between gas pressure and the pressure corresponding to the gas temperature
d. coil pressure

Superheat is heat added
a. in changing liquid vapor
b. in raising temperature of water
c. after all liquid has been changed to vapor
d. to increase pressure

The feeler bulb of a TXV is located
a. before the evaporator
b. after the evaporator
c. midway along the evaporator
d. on the suction line next to the compressor

An automatic expansion valve system on variable loads causes
a. a flooded evaporator on high loads
b. no apparent change in operation
c. an overloading of the compressor motor
d. a starved evaporator at high loads

The TXV valve has three operating pressures
a. evaporator pressure

One main disadvantage of an automatic expansion valve is that it
a. requires a critical charge of refrigerant
b. is only used on domestic refrigerators
c. cannot adapt to variable loads
d. all of the above