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Fundamentals of Refrigeration 5

Total questions: 20

Worksheet time: 10mins

Name
Class
Date
1.

An automatic expansion valve is a metering device used for feeding the refrigerant into an evaporator. It uses an adjustable spring pressure working to open the refrigerant valve balanced against the evaporator pressure beneath a diaphragm working to close the valve. Its function is to maintain a constant pressure, and thereby, a constant _______ in the evaporator.

a)

temperature

b)

flow rate

c)

humidity

d)

volume

2.

The AEV begins by injecting liquid refrigerant into the inlet of the evaporator until a predetermined pressure is reached, at which point it _______. As the refrigerant boils away, the valve opens and injects more refrigerant to prevent a drop in suction pressure.

a)

shuts off

b)

opens fully

c)

increases speed

d)

reverses flow

3.

An increase in evaporator pressure above the spring pressure closes the valve. A decrease in pressure allows the spring to _______ the valve.

a)

open

b)

close

c)

tighten

d)

lock

4.

The evaporator has no definite liquid charge or frost line. Rather, the liquid gradually works its way through the evaporator, then if it is not stopped, it comes out into the suction line and eventually into the compressor.

a)

True

b)

False

5.

An AEV system is properly charged when a small reserve of liquid is present in the receiver tank just as the liquid level comes out of the _______.

a)

evaporator

b)

compressor

c)

condenser

d)

expansion valve

6.

True or False: More than one AEV can be used on a system. It can be paralleled with other metering devices such as thermostatic expansion valves, capillaries or floats.

a)

True

b)

False

7.

The AEV closes tightly as soon as the compressor stops. Specially constructed 'bleeder' valves can be purchased to use with _______ phase motors.

a)

split

b)

single

c)

three

d)

dual

8.

The AEV should be installed at the top of the evaporator to provide a down drain in order to prevent the accumulation of _______.

a)

oil

b)

water

c)

dust

d)

ice

9.

The capacity of an AEV will be determined by the size of the orifice in the valve and the pressure drop across the _______.

a)

valve

b)

compressor

c)

condenser

d)

evaporator

10.

A low pressure control cannot be used with the AEV.

a)

True

b)

False

11.

If the pressure-temperature setting on a HFC-134a system is 8 PSIG and 3°F with a 6° differential, what is the cut out range?

a)

8° - 13°

b)

14° - 19°

c)

3° - 8°

12.

The AEV is operated by which two pressures?

a)

Hydraulic and pneumatic

b)

Atmospheric and vacuum

c)

Hydraulic and atmospheric

d)

Pneumatic and vacuum

13.

The function of the AEV is:

a)

To provide energy to the vehicle

b)

To control the speed of the vehicle

c)

To transport goods autonomously

d)

To monitor the vehicle's environment

14.

What will happen to the frost line on an AEV system if a heavy load is placed on the evaporator?

a)

The frost line will move further along the evaporator.

b)

The frost line will move closer to the expansion valve.

c)

The frost line will disappear completely.

d)

The frost line will remain unchanged.

15.

What type AEV must be used with split phase motors?

a)

Manual AEV

b)

Magnetic AEV

c)

Thermal AEV

d)

Electronic AEV

16.

The capacity of an AEV is determined by:

a)

The amount of energy it can store

b)

The number of wheels it has

c)

The color of the vehicle

d)

The speed it can reach

17.

You have an AEV system with a thermostatic motor control installed and you have liquid refrigerant all the way to the compressor. What is the problem?

a)

The expansion valve is stuck open

b)

The compressor is not running

c)

The evaporator is overcharged

d)

The condenser is blocked

18.

The setting on your AEV for a HFC-134a system is 17.1 PSIG and 18° with a differential of 8°. What are your cut in and cut out temperatures?

a)

Cut in: 18°, Cut out: 10°

b)

Cut in: 17.1°, Cut out: 9.1°

c)

Cut in: 18°, Cut out: 26°

d)

Cut in: 10°, Cut out: 18°

19.

Indicate which of the following is a sign of a properly charged AEV system:

a)

Low refrigerant pressure

b)

Frost on the evaporator

c)

Correct operating pressures and temperatures

d)

Continuous compressor cycling

20.

A low pressure control should be set to operate with an AEV system by:

a)

Setting the cut-in pressure above the normal operating pressure

b)

Setting the cut-out pressure below the normal operating pressure

c)

Setting the cut-in pressure below the normal operating pressure

d)

Setting the cut-out pressure above the normal operating pressure