Unit 23 Compressors Quiz

The piston of a reciprocating compressor must make ___ stroke(s) to complete one cycle of refrigerant compression.

2

The discus valve design is more efficient than a flapper valve design because ___

it allows a compressor design with less clearance volume.

If the compression ratio of a system with a reciprocating compressor decreases, the amount of refrigerant pumped by the compressor ___

will increase.

What is the compression ratio at these conditions? Discharge pressure: 282.3 Evaporator pressure: 49.3 Condenser pressure: 277.3 Suction pressure: 51.3

4.5

At a constant RPM, a compressor is a constant displacement device and its capacity is constant.

False

Compressors are not designed to compress liquids because pumps already exist for that purpose.

False

Rotary compressors have pistons that rotate inside the cylinders.

False

Scroll compressors are becoming popular because they can handle liquid flood-back without compressor damage.

False

The hermetic reciprocating compressor motor is essentially made of the same materials as an open type compressor motor.

False

The higher the rpm of a compressor, the higher the pumping efficiency.

False

The most common method(s) of capacity control for rotary compressors are motor speed control and on-off cycling.

False

The pattern of gas movement through a scroll compressor is from the center toward the perimeter.

False

The scroll compressor is one type of reciprocating compressor.

False

The sight glass on a semi-hermetic compressor is used to allow light to enter the crankcase to keep the oil warm.

False

A bolted together motor-compressor assembly is sometimes referred to as a semi-hermetic type.

True

At a constant RPM, a compressor is a constant displacement device and its capacity is variable.

True

Rotary compressors have no "clearance volume".

True

The compressor in the mechanical refrigeration system is much like the heart in the human body.

True

The suction and discharge valves in a reciprocating compressor open and close depending on the difference in pressure across them.

True

If the suction valve in a reciprocating compressor is leaking slightly, the ____

cooling capacity will be reduced & compressor can overheat.

Liquid entering the compression chamber of a reciprocating compressor can lead to ___

damaged valves & damaged piston rings

Rotary compressors are used primarily in __

domestic refrigerators.

The reciprocating compressor has a built-in problem with inefficiency which results from:

its clearance volume.

The screw-type compressor is used primarily in ___

large industrial refrigeration and air-conditioning systems.

Mos of the heat energy in the suction vapor entering the compressor is ___

latent heat.

The clearance volume of a compressor ____

remains the same as the compression ration decreases.

All but which one of these things happens as a direct result of the compressor doing its work?

the air is adequately circulated in the conditioned space.

What could happen if a semi-hermetic compressor is operated with the suction service valve back-seated and the discharge valve front-seated?

the head of the compressor may blow off.

The temperature of the compressed gas leaving the compressor can best be described as ___

very warm.

The clearance volume of a compressor cylinder is the ___

volume of the space between the bottom of the valve plate and the top of the piston at top dead-center.