Tpc 434 Evap And Metering Devices

Question 1

The function of an evaporator is to _____
heat (from/to) the _____

add; condenser
add; refrigerant
remove; material being cooled
remove; refrigerant

Answer 1

remove; material being cooled

Question 2

The capacity of an evaporator is affected by the

amount of insulation surrounding the material being cooled
cleanliness of the evaporator
type of refrigerant used
weight of the evaporator

Answer 2

cleanliness of the evaporator

Question 3

Basic evaporator configurations depend on whether they have one or more tubes and whether or not they have

extended surface areas
headers at both ends
insulated tubes
more than one compressor

Answer 3

extended surface areas

Question 4

Multiple-circuit evaporators have headers or distributors that direct refrigerant to each coil from ______
expansion valve(s).

alternating
one
selected
two or more

Answer 4

one

Question 5

A comfort cooler _____ the humidity of moist air by cooling the air to a temperature _____ the dew point.

increases; above
increases; below
reduces; above
reduces; below

Answer 5

reduces; below

Question 6

Unlike a dry expansion evaporator, refrigerant in a flooded evaporator enters as _____ liquid and exits as ____vapor.

all; all
all; part
part, all
part; part

Answer 6

all; part

Question 7

A eutectic solution is a brine in which the concentration of salt is precisely set to achieve the lowest possible

boiling point
temperature
freezing point
vapor pressure

Answer 7

freezing point

Question 8

Which evaporator arrangement offers the greatest flexibility?

Single evaporator, single expansion valve
Two evaporators in series
Two evaporators in parallel with a common expansion valve
Two evaporators in parallel, each with its own expansion valve

Answer 8

Two evaporators in parallel, each with its own expansion valve

Question 9

A cascade refrigeration system has more than one

compressor
compressor, evaporator, condenser, and refrigerant
evaporator and condenser
refrigerant

Answer 9

compressor, evaporator, condenser, and refrigerant

Question 10

The basic laws) of thermodynamics that apply to refrigeration state that

compressing a gas lowers its temperature
cooling is the reverse of heating
heat flows from a warmer substance to a cooler substance
subcooling always equals superheating

Answer 10

heat flows from a warmer substance to a cooler substance

Question 11

The net refrigeration effect can be increased by ____ the refrigerant.

decreasing the charge of
decreasing the velocity of
increasing the charge of
subcooling

Answer 11

subcooling

Question 12

Using a heat exchanger to lower the temperature in the liquid line and raise the temperature in the suction line has the advantages) of reducing

the amount of liquid refrigerant entering the compressor
the pressure in the suction line
hunting by the metering device
the temperature in the condenser

Answer 12

the amount of liquid refrigerant entering the compressor

Question 13

The amount of oil entering an evaporator can be reduced by using a(n)

filter-dryer
flooded evaporator
oil separator
oil skimmer

Answer 13

oil separator

Question 14

If the fluid being cooled by an evaporator circulates through the coil rather that moving slowly or not at all, the performance of the evaporator improves because of the

counterflow of the fluid and the refrigerant
increased temperature difference across the wall of the evaporator
reduced temperature difference across the wall of the evaporator
turbulence around the coils

Answer 14

increased temperature difference across the wall of the evaporator

Question 15

An evaporator can be defrosted by

circulating cooled air over the coils
reducing the load on the system
reversing the flow of refrigerant
spraying liquid refrigerant on the coils

Answer 15

reversing the flow of refrigerant

Question 16

To remove rust, scale, and sludge from a shell-and-tube evaporator you should use an) _____ ,as necessary

brush
drill bit
hammer and chisel
round scraper

Answer 16

brush

Question 17

A water coil can be winterized by draining out the water and

installing a thermostat
leaving the coil dry for the winter removing any ice
replacing it with warm water daily

Answer 17

leaving the coil dry for the winter

Question 18

Frost buildup on an evaporator coil is increased by ____ airflow and ____ air

low; dry
low; humid
high; dry
high; humid

Answer 18

low; humid

Question 19

Bent fins reduce the cooling capacity of an evaporator, because they ______

increase the area exposed to the air
reduce the refrigerant flow to the suction line
reduce the area exposed to the air
trap heat near the coil

Answer 19

reduce the area exposed to the air

Question 20

The purpose of the metering device in a refrigeration system is to

control the flow of refrigerant into the evaporator
measure the refrigerant flow-rate
prevent excessive liquid-line pressure
warn of system low pressure

Answer 20

control the flow of refrigerant into the evaporator

Question 21

In controlling the flow of refrigerant into a flooded evaporator, the float of a high-side float valve Is located [at/on] the

highest elevation in the system
high-pressure side of the valve port
top of the condenser
top of the evaporator

Answer 21

high-pressure side of the valve port

Question 22

If floodback occurs in a system using an AXV, a likely cause IS

bent evaporator fins
dirty evaporator coils
ice on the spring chamber above the diaphragm
refrigerant undercharge

Answer 22

ice on the spring chamber above the diaphragm

Question 23

A common problem with TXVs is ice in the valve port. The proper way to correct this problem is to _____

add refrigerant to the system
replace the filter-drier
replace the system oil
remove refrigerant from the system

Answer 23

replace the filter-drier

Question 24

The operation of an AXV is controlled by the

pressure in the evaporator
pressure at the suction line temperature at the suction line
temperature in the evaporator

Answer 24

pressure in the evaporator

Question 25

In a secondary-refrigeration system, the refrigerant removes heat from the material to be cooled. This refrigerant then transfers heat to the ____ refrigerant. In the process, the ____refrigerant boils. • primary; primary; • primary; secondary; • secondary; primary; • secondary; secondary;

Answer 25

secondary; primary;