Unit 23 Quiz Flashcards

1
Q

If the compression ratio of a reciprocating compressor increases, the amount of refrigerant pumped by the compressor ________.

A

Will decrease

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2
Q

What component connects the piston to the crankshaft in a reciprocating compressor?

A

Connecting rod

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3
Q

Flank sealing takes place in a ______ compressor.

A

Scroll

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4
Q

The hermetic compressor shell is typically thought of as a _______ component.

A

Low side

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5
Q

Two-stage compression is not generally used until the compression ratio exceeds 10:1, often experienced with __________.

A

Low temperature refrigeration

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6
Q

What is the function of the compressor in a refrigeration system?

A

It is a vapor pump that converts low pressure low temperature vapor into high pressure high temperature vapor

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7
Q

Compute the compression ratio using 14.7 psi as the conversion factor when the suction pressure is -3.1 psig and the discharge pressure is 198.9 psig for a low temp system using R-404A.

A
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8
Q

True or false: A semi-hermetic compressor can be taken apart and serviced.

A

True

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9
Q

True or false: The screw compressor uses an open motor instead of the hermetic design.

A

True

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10
Q

True or false: Motors for hermetic compressors are manufactured with the same materials as standard electric motors that operate in an open-air environment.

A

False

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11
Q

True or false: The rotary screw compressor is another name for the rotary type compressor.

A

False

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12
Q

True or false: To keep refrigerant vapor from leaking over the top of the scrolls, tip seals are used.

A

True

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13
Q

True or false: The centrifugal compressor is a positive displacement type compressor.

A

False

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14
Q

True or false: High compression ratios above 12:1 are not recommended by most manufacturers.

A

True

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15
Q

True or false: Open drive compressors are manufactured in two styles, belt driven or gear driven.

A

False

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16
Q

True or false: The discus valve in a reciprocating compressor has a smaller clearance volume than reed/flapper valves.

A

True

17
Q

True or false: The scroll compressor takes a fixed volume of gas at a suction pressure and then maintains the same gas volume to increase its pressure.

A

False

18
Q

True or false: A two-step scroll compressor uses motor speed to control cooling capacity.

A

False

19
Q

List four causes that may lead to liquid refrigerant entering the compressor.

A

Broken evap fan,
broken metering,
dirty air filter,
overcharging

20
Q

Where would you check an open drive compressor for a possible refrigerant leak?

A

Shaft seal

21
Q

An electric motor is connected to an open compressor that is rated for 50 tons using R-22 refrigerant. The drive pulley is 5 inches in diameter and spins at 3600 rpm. The compressor needs to run at 1750 rpm. What is the diameter of the pulley on the compressor?
(drive pulley size x drive pulley rpm = driven pulley size x driven pulley rpm)

A
22
Q

A disengaging solenoid valve is used to vary cooling capacity in a scroll compressor. What is the external feature that distinguishes a digital capacity scroll compressor from a two-step capacity scroll compressor?

A

Solenoid valve, outside compressor

23
Q

Used to suppress compressor pulsating noises.

A

Muffler

24
Q

Holds the suction and discharge valves.

A

Valve plate

25
Q

Belt or direct drive. Must have a shaft seal to keep refrigerant from escaping.

A

Open compressor

26
Q

Determines the direction the gas entering the compressor will flow.

A

Refrigerant cylinder valves

27
Q

What external feature on the exterior of a compressor identifies it as a two-stage compressor that will utilize the Y2 terminal in the thermostat?

A

Two electrical connectors on each side

28
Q

Which compressor doesn’t have a clearance volume and is more efficient than a reciprocating compressor?

A

Screw, rotary, centrifugal

29
Q

Why is it bad to start a hermetic compressor when it is in vacuum? Explain in detail.

A

Starting a hermetic compressor while in vacuum may cause an explosion due to
Terminal Venting

30
Q

Which type of v-belt is better at dissipating heat when used around small pulleys?

A

Cog belt

31
Q

A 3-phase internal thermal overload will disconnect all three of the overload contacts at the same time if a motor overheating problem occurs. What happens if only one of the overload contacts opens?

A

Two of contacts will remain in circuit, resulting in overheating and high current draw