Last Updated on May 15th, 2021 by RefrigeratorPro Team
Refrigeration systems are basically heat engines working in reverse. It means that the heat transfer takes place from colder region to hotter region for creating cooling effect in the surroundings.
Before we start, we have to understand that refrigerant and its movement inside the coils is responsible for exchange of heat. Basic principle is quite simple. The refrigerant absorbs heat from the surroundings to produce cooling effect and then releases the heat outside the system through the condenser.
This animated gif gives a decent idea about refrigeration cycle in a window AC. Let’s see how this cycle works in more detail.
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Table of Contents
- Refrigeration Cycle
- Refrigeration Cycle – FAQs
The Refrigeration Cycle takes place with the help of four major components: compressor, condenser, evaporator and expansion valve / throttle valve.
Step 1: Compression [Heating Up]
The gaseous refrigerant enters the compressor at low temperature and low pressure. This compressor compresses the refrigerant to increase its temperature and pressure. Further, this compressor helps in moving the refrigerant into the condenser.
These compressors can be of four major types- reciprocating, rotary-vane, rotary-screw or centrifugal.
Step 2: Condensation [Heat Release]
The condenser is a network of pipes that helps in condensation process of the refrigerant. It means that the hot gaseous refrigerant starts losing heat. This heat actually get released into the air surrounding the condenser. That’s why air is usually hot around condensers of refrigerators, ACs etc. Even though the heat gets released, this refrigerant is still in constant pressure.
Step 3: Expansion [Further Cooling]
Expansion is opposite of compression. This means that as soon as the refrigerant enters the expansion valve, it expands and this leads to reduction in both temperature and pressure drastically. Due to this, it now converts into liquid-gas mixture. This expansion valve controls the amount of liquid refrigerant that enters the evaporator.
Step 4: Evaporation [Heat absorption to Cool the Surroundings]
This is the final stage where the refrigerant cools the surrounding region by absorbing heat. Since the refrigerant is already colder than surroundings, it automatically starts absorbing heat. Further, the compressor also helps in keeping the pressure of the refrigerant low.
This is how the refrigerant cools its surroundings. Once the refrigerant absorbs heat, it turns into gas and gets transferred back to the compressor and the cycle continues.
Simpler applications with fixed operating temperatures, such as a residential refrigerators, can use fixed speed compressor and regular expansion valve. However, applications that varied conditions, such as through different seasons, have started using inverter compressors that run at variable speeds and adjustable expansion valves to control the refrigerant pressure and temperature more accurately.
Refrigeration Cycle – FAQs
This was a simple explanation of how refrigeration cycle works with the help of refrigerants. It’s natural that you may have more questions. Don’t worry, we have answered some of the key questions you may have.
What is the need to compress the refrigerant?
Refrigerant absorbs the heat and then releases it into the surroundings. For heat to get releases into the surroundings, there should be substantial difference between refrigerant and surrounding air.
Compression process is necessary because if the refrigerant is not compressed and super-heated, then the temperature of the refrigerant will be similar to room temperature. This means that heat will not get released into the surroundings.
How does expansion valve reduce temperature of the refrigerant?
A valve is a device that allows partial flow of a liquid or gas. The expansion valve restricts the amount of refrigerant that flows through it at a given time. Due to this, less volume of refrigerant gas passes through the valve into next section of the pipe, which allows it to expand. And this expansion leads to reduction in temperature because the refrigerant has to spend some amount of energy to expand!
Does refrigerant have low boiling point?
A refrigerant has very low boiling point. It can be as low as minus 23 degrees Celsius. This means that as soon at the refrigerant enters the evaporator, it boils and evaporate in very short time as it absorbs heat from the surroundings. This is necessary because if the boiling point of the refrigerant is high, the compressor will have to work extra hard to convert it into high pressure liquid.
What type of refrigeration cycle is used in home appliances?
Most home appliances use vapour-compression refrigeration cycle for cooling.
Can water be used as a refrigerant?
Yes, water can be used as a refrigerant, but it is usually not used for residential appliances and a primary reason for this is its high boiling point. This means that a really powerful compressor will have to be designed for it heat and pressurize water. This will make it uneconomical and less efficient.