Metering devices

An automatic expansion valve uses a thermal bulb to help control the amount of refrigerant being fed into the evaporator. True False

False

As the load on an evaporator increases, the automatic expansion valve will open to allow more refrigerant to enter the evaporator. Selected Answer: True False

False

A system has a suction line of 1 3/8" , what is the proper method to mount the sensing bulb?

Mechanically at 4:00 or 8:00

You go on a service call to a system with a TXV, not cooling well. You determine that you have high suction superheat leaving the evaporator. What is the next thing you should check?

System subcooling to check the refrigerant charge

An AX valve works best when the evaporator load is constant. Selected Answer: True False

True

The pressure in a refrigeration system is changed in the ____. a. compressor and expansion device b. expansion device and evaporator c. condenser and evaporator d. condenser and compressor

a. compressor and expansion device

When the load on the evaporator increases, the TX valve ____. a. increases the flow of refrigerant b. decreases the pressure drop across the evaporator c. maintains constant head pressure d. decreases the flow of refrigerant

a. increases the flow of refrigerant

A thermostatic expansion valve controls refrigerant flow to the evaporator based on ____. :a. rate of liquid vaporization b. evaporator suction line superheat c. external equalizer pressure d. all of the above

b. evaporator suction line superheat

What three pressures control the operation of a thermal expansion valve?

bulb pressure, evaporator pressure, spring pressure

Name the six essential parts of a thermal expansion valve.

bulb, power head, push rod, seat & pin, spring, adjustment stem

A ton of refrigeration is equal to ____. a. 12000 Btu/min. b. 144 Btu/hr c. 288000 Btu/24-hr. d. 1 ton of ice

c. 288000 Btu/24-hr

The TXV sensing bulb is mounted ____. a. at the inlet to the condenser b. on the compressor discharge line c. on the suction line as close to the evaporator outlet as possible d. on the liquid line between the condenser and the TX valve

c. on the suction line as close to the evaporator outlet as possible

If the power element of a TX valve loses its charge, the ____. a. refrigerant flow through the various circuits of the coil will become unbalanced b. valve will get cold enough to create frost on the body of the valve c. refrigerant flow to the coil will stop d. coil will flood enough to feed liquid refrigerant out of the coi

c. refrigerant flow to the coil will stop

The four (4) major components of a vapor compression refrigeration system are the ____________________, ____________________, ____________________, and ____________________.

compressor, condenser, evaporator, expansion device

The primary purpose and function of an expansion device is to ____. a. seperate the high side from the low side b. regulate the flow of refrigerant into the evaporator c. lower the boiling point of the refrigerant far enough below the temperature of the load to get the needed heat transfer rate d. all of the above

d. all of the above

The purpose of a capillary tube is to ____. a. regulate the refrigerant flow into the evaporator b. lower the pressure of the liquid refrigerant c. lower the boiling point of the refrigerant d. all of the above

d. all of the above

At what location or locations in a refrigeration system does the saturation pressure correspond to the saturation temperature? a. compressor and evaporator b. condenser and expansion device c. compressor d. evaporator and condenser

d. evaporator and condenser

Name four different types of metering devices.

hand, automatic, cap tube, TXV, low side float, high side float, EXV

When the quantity of refrigerant flow to an evaporator is reduced, evaporator pressure decreases, therefore the amount of superheat leaving the coil will ____________________.

increase

Turning the adjustment stem clockwise on a TXV will have what effect on suction superheat leaving the evaporator.

increase the superheat

The automatic expansion valve maintains a constant ____________________.

pressure

What is the most common failure of a thermal expansion valve?

sensing bulb loosing its charge

The two pressures that push to close a thermostatic expansion valve are the ____________________ pressure and the ____________________ pressure.

spring, evaporator

The refrigerant vapor picks up additional heat as it flows from the evaporator outlet to the compressor. The heat is picked up from the ____________________.

suction line