Refrigeration Compressors: Function, Types, Advantages And Disadvantages

In this article, I will share the functions of refrigeration compressors, types, advantages and disadvantages of these types of compressors.


The compressor is another important part of the refrigeration system that completes the refrigeration cycle.


Without wasting time, let me share the function of compressors in a refrigeration system.


Functions of refrigeration compressors;

1. Draws the refrigerant from the evaporator.

It’s the function of the compressor to draw the refrigerant from the evaporator after it has expanded after absorbing heat from the body to be cooled.


The compressor sucks the refrigerant from the evaporator and forces it to the condenser to keep the circulation going.


So, from this, we can say that the compressor also aids the refrigerant to keep on flowing in the refrigeration cycle since the compression process increases the pressure of the refrigerant.


It does that by compressing the refrigerant thus exerting a force that keeps the refrigerant flowing to the condenser.


2. It reduces pressure in the cooling coil of the condenser.

The compression of the compressor reduces pressure in the cooling coil of the condenser to allow the refrigerant to boil and thus absorb heat.


This ensures that the refrigerant absorbs enough heat and ends up being sufficiently cooled as it’s leaving the condenser.


If the pressure in the cooling coil of the condenser would be high, then the cooling process of the refrigerant would be less effective.


3. It increases the temperature of the refrigerant.

The compressor increases the temperature of the refrigerant during compression.


When the refrigerant temperature is increased during the compression process, it increases the energy content of the refrigerant thus resulting in efficient heat absorption and effective cooling as it leaves the condenser.


Types of compressors.

  • Reciprocating compressors.
  • Rotary compressors.
  • Centrifugal compressors.


In this article, I won’t talk much about the above compressors since I wrote entire articles about them.


You can read the articles in the links below.


You might like this: Reciprocating Air Compressor: Components, Types And Working Principle, Centrifugal Air Compressor: Components And Working Principle


When it comes to a situation where the compressor and motor are running on the same shaft and are enclosed in the same casing, these types of compressors are called hermetic sealed compressors.


Advantages of hermetic sealed compressors.

1. The leak of the refrigerant is prevented.

Since the motor and the shaft are using the same casing and are running on the same shaft, this provides a seal that prevents the refrigerant from leaking.


2. It requires a small space.

The fact that the compressor and motor are enclosed in the same casing brings about its compactness and thus ends up occupying less space.


It’s very different from when the motor and compressor have their own casings and they are operating on different shafts.


This design of the compressor makes it possible to occupy a small space in the refrigeration system.


3. Lubrication is simple.

Lubrication in hermetic sealed compressor is simple because the compressor and the shaft operate on the same shaft.


So, when one applies the lubrication on one part of the shaft, the oil can reach the compressor and the motor at the same time.


The other thing is that one will use less lubricant compared to when the motor and compressors are operating on different shafts.


This brings about conservation of the lubrication oil thus saving money and time.


Another thing that makes the lubrication simple is that the motor and compressor operate under one sealed space with the lubricating oil.


4. Compressor vibration is felt outside.

The vibration of the compressor when it’s operating is not appropriate for the refrigeration cycle.


The forces that are emitted by the compressor will reduce the efficiency of the refrigeration cycle.


Hermetic sealed compressor has a spring-mounted design within the refrigeration system thus allowing the vibration to be emitted outside of the refrigeration system.


This allows smooth flow of the refrigerant in the refrigeration cycle thus maximizing cooling.


Disadvantages of using hermetic sealed compressors;

1. Motor accessibility is hindered.

Since the motor and compressor are sealed within the same casing this means the motor is not accessible thus making maintenance of the motor an issue.


If by any chance it happens that the motor has an issue, one will have to dismantle the whole casing.


This will waste time and the maintenance will be tiresome because the compressor and the motor all operate under the same shaft.


This would have been different if the motor and compressor were in different casings and operate on different shafts.


2. Failure of the motor would cause a disaster.

Since the motor and compressor operate under the same shaft, when the motor fails then there will be product decomposition and contamination at the same time.


You have to know that when the motor fails, the compressor will end up settling the refrigerant within the casing, which will cause decomposition.


The motor is usually in charge of keeping the products within the compressor moving, that is one thing you have to understand.


Contamination will also happen when the motor fails because the shaft will start allowing the flow of the refrigerant to the motor.


And this will lead to massive contamination.


This wouldn’t have been an issue if the motor and compressor were separated.


3. Cooling of the motor becomes a problem.

The fact that the motor and shaft operate under the same shaft and are enclosed in the same casing cooling will eventually be an issue.


The compression process releases heat and also as the motor is operating the heat is added up.


This will bring an issue to the motor because the heat will be higher within the casing.


The cooling of the motor depends on the gas entering the compressor, so, if by any chance the gas is not cold enough to cool the motor then the refrigeration system will be at fault.


If the motor overheats it can end up shutting down and this will temper the entire refrigeration system.


So, cooling of the motor in hermetic sealed compressor is an issue that one should carefully check on if he or she intends to use this type of compressor.


4. Two pumps will be needed for evacuation and charging.

Separate pumps will be required for evacuation and charging of the refrigerant because of the fact the motor and compressor operate under the same shaft and are in the same casing.


Methods of capacity controls used in refrigeration compressors.

To control the amount of refrigerant drawn from the evaporator or pumped to the condenser, the compressor needs capacity controls.


These are the methods used to control the capacity of compressors;


  • Hot gas bypass system.
  • Variable speed method.
  • Compressor cylinder unloading.
  • Gas-actuated unloaders/suction valve lifting.


Final thoughts.


This is just a summary of the compressors used in the refrigeration system.


There is so much to learn when it comes to these compressors. If I decide to write everything about compressors then I would have this website filled with compressors.


What you need to know is that there is so much to learn from the compressors, so dig deep in books and do some research if you want to know anything more.


If you have any questions about what I have talked about in this article just leave your comment.


Thanks for reading, see you in my next article.


Related articles to check.

  1. Refrigeration Evaporators: Functions, Types, Design Characteristics And Maintenance.
  2. Two Stage Refrigeration Cycle Using A Flash Chamber: Working Principle
  3. Refrigeration Condensers: Functions, Types & Maintenance
  4. Vapour Absorption Refrigeration System: Working Principle
  5. Causes Of Vapour Compression Refrigeration System Failure +Solutions

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