Refrigeration Licences Review

In a well designed compressor the percent of lubricant circulated should not exceed

10%.

360000 B.T.U.S would be removed in a

30 ton system.

Efficient of the refrigeration cycle is affected by the operation of the condenser.

A more efficient operation of centrifugal compressor results from lower condenser pressure.

Clearance volume

Affects compressor capacity.

The cylinder unloader controls capacity

Assisting with compressor start up is another function it may have.

A refrigeration unit is measured in

B.T.U.S

High condenser temperature and low condenser water temperature will

Cause the greatest BTUs absorbed by the condenser water.

The solenoid unloaders on reciprocating compressors are

Designed to unload the clearance spaces in the cylinders.

The centrifugal compressor generates

High volume and low pressure (relative) inside.

if you were running three compressor

Highly super heated vapor describes the state of refrigerant leaving the third compressor.

Non-condensable vapors collect

In the condenser.

The condenser that uses air and water for cooling

Is the evaporative type.

If you sub-cool the refrigerant

It will enhance refrigeration effect.

Shell and coil condensers have the advantage of having

Less of a chance of developing leaks.

Oil foaming in the compressor is a result of

Liquid refrigerant in the crankcase.

If unloaders were to fail in the unloaded position

Not enough refrigerant will flow to the evaporator coil, the evaporator will then starve, causing high superheat in a system using a reciprocating compressor.

Superheated vapor flowing into reciprocating compressor protects the compressor parts against liquid intake.

One of the problems associated with superheat is that it will decrease the capacity of the compressor and the refrigeration machine.

An operator has been assigned to run a reciprocating compressor

Opening the suction valves with some form of control is the most likely achieved action of capacity control.

When a system does not have unloaders,

Other capacity control is needed.

Unloaders are used to

Reduce capacity.

At the condenser

Refrigerant enters as high pressure gas and leaves as high pressure liquid.

The ratio of actual pressure of water vapor in the atmosphere to the saturation pressure/temperature is called

Relative humidity.

Superheated vapor protects the compressor against liquid intake.

The RMO would notice frost that may develop in the suction line if the compressor was receiving liquid.

An operator has been assigned to run a centrifugal compressor

The capacity control most likely achieved is through adjustment of the impeller inlet guide pre-rotation vanes.

The dividing line between the high and low sides of the refrigeration system is

The compressor outlet and the orifice of the metering device.

If a centrifugal compressor is being used in a refrigeration system, and is effected by the condenser

The condenser may be improved by increasing the amount of sub-cooling.

Low evaporative and low condenser temperature are

The conditions that would cause the greatest heat in BTU/HR MIN absorbed by the condenser water in a refrigerating plant.

Refrigerant oil quality is measured in viscosity

The last desirable quality in the oil would be low viscosity.

In a 3 stage centrifugal chiller

The pressure increases as it reaches the final stages.

In relation to the suction pressure of a compressor,

The reading of the oil pressure gauge should read 15-30 psi higher.

Shell and tube condenser have the advantage of when removing heads for cleaning the water side of the tubes

The refrigerant connections do not have to be disrupted.

if the refrigerant is entering the sub-cooling tubes of the condenser as a gas

Then the system is short of refrigerant.

Oil in a refrigeration system reduces

Wear and friction.

If you just purchased a thermometer and need to check to see if it's working

You would touch it to a bucket of ice/ice water.

A mechanical seal is

a shaft seal that prevents vapor from leaking out of compressor.

Semi-hermetic compressors may be better to use than hermetic compressor,

because hermetic compressors are fully enclosed and cannotbe serviced on site.

In a centrifugal three stage compressor impellers are the same size,

but the pressure increases with each stage.

Tip speed is more with

each stage of a multistage centrifugal compressor.

When changing water to ice

latent heat must be remove

Any heat that boils off is

latent heat.

A pressure relief valve that is installed on a reciprocating compressor using R-12 is normally

set according to design pressure.

The state of refrigerant as it leaves the compressor is

super heated vapor and as it leaves the condenser is warm sub-cooled liquid.

Compressor motors that operate inside the refrigerant atmosphere (atmospheric) must

use materials compatible with the system refrigerants, motor must be assembled in clean atmosphere and keep dry, and or not working on in the field.