Ultimate Guide to HVAC Vapour Absorption Refrigeration Systems [PDF]


In this comprehensive guide, we will be discussing how vapor absorption refrigeration systems work, the types of vapor absorption refrigeration systems, the advantages and disadvantages of using them, their applications, the difference between vapor compression refrigeration systems (VCRS) and vapor absorption refrigeration systems (VARS), and how to maintain and troubleshoot them.

What is a vapour absorption refrigeration system?

Before we dive into how vapor absorption refrigeration systems work, let’s start by defining what it actually is. A vapor absorption refrigeration system is a type of refrigeration system that uses a refrigerant and an absorbent to create a refrigeration effect.

vapour absorption refrigeration system
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The refrigerant and absorbent work together to transfer heat from one area to another, thereby cooling the desired space. Vapor absorption refrigeration systems are often used in industrial applications, but they are also becoming increasingly popular in residential use.

Working of a vapour absorption refrigeration system

In vapor absorption refrigeration systems, the refrigerant and absorbent are circulated continuously through the system. The refrigerant is typically ammonia or lithium bromide, while the absorbent is usually water. The system works by using heat to drive the refrigeration process. The process starts with the evaporator, where the refrigerant absorbs heat from the surrounding area and evaporates, creating a low-pressure vapor. The low-pressure vapor then moves to the absorber, where it is absorbed by the absorbent. The absorbent now contains both the refrigerant and heat.

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The next step is to remove the heat from the absorbent. This is done by using a heat source, such as a gas burner or solar energy, to heat the absorbent. The heat causes the refrigerant to evaporate from the absorbent, which creates a high-pressure vapor. The high-pressure vapor then moves to the condenser, where it is cooled, and the refrigerant returns to its liquid state. The final step is to return the refrigerant to the evaporator, where the cycle begins again. This continuous cycle of evaporation, absorption, heat removal, and condensation is what creates the refrigeration effect.

Types of vapour absorption refrigeration system

Following are the types of Vapor Absorption Refrigeration Systems :

  • Single Effect.
  • Double Effect
  • Tripple Effect

Let us discuss each type in detail.

Single Effect Systems

Single-effect systems use one generator to heat the absorbent and create the refrigeration effect. It operates on the principle of evaporation and condensation. Here typically water is used as a refrigerant to absorb and then send it back it the generator. It operates on a continuous cycle. Heat absorption happens in the evaporator and released in the generator.

Double effect systems

Double-effect systems use two generators. This system uses a liquid absorbent. Generally lithium bromide is used to provide the chilling effect. Water is first vaporized and then passed through a heat exchanger. The solution is then sent back to second generator. It is heated at a lower temperature. This is a double effect vapor absorption system. They are widely used in large commercial applications.

Triple effect systems

Triple effect systems use three generators. At the start the initial generator is heated using an industrial process or solar energy. This vaporizes and transfers to absorbent solution. Similarly the cycle is repeated. They are generally used in large industrial and commercial applications such as production plants. They are used with cogeneration systems to recover waste and provide cooling.

Advantages of vapor absorption refrigeration systems

Following are the advantages of vapor absorption refrigeration systems

  • They use natural refrigerants like ammonia and water which are environmentally friendly
  • They have a low global warming potential.
  • They also have a low operating cost
  • They can be powered by a variety of heat sources including natural gas, propane, and solar energy.
  • Vapor absorption refrigeration systems are versatile
  • They can be used in a variety of applications, including air conditioning, refrigeration, and heat recovery.

Disadvantages of vapor absorption refrigeration systems

Following are the disadvantages of vapor absorption refrigeration systems :

  • They are less efficient than vapour compression refrigeration systems.
  • They tend to be larger and more complex
  • They are more difficult to install and maintain.
  • They require a heat source to operate which can be a challenge in colder climates.

Applications of vapour absorption refrigeration systems

Following are the applications of a vapor absorption refrigeration systems :

  • Vapor absorption refrigeration systems are commonly used in industrial settings, such as chemical plants and oil refineries,
  • They can be powered by waste heat from industrial processes.
  • They are becoming increasingly popular in residential settings as a more environmentally friendly alternative to traditional refrigeration systems.
  • Using this in a car will reduce the fuel consumption as well as increase the efficiency of engine.

Difference between vapour compression refrigeration systems and vapour absorption refrigeration systems

Vapor Compression SystemVapor Absorption System
In a vapor compression system a compressor is used to compress the refrigerant such as R-410A.In a vapor absorption cycle a liquid absorbent is used such as lithium bromide.
They are most commonly used in commercial and residential applications.They are used in large scale applications where waste heat is available for use.
They have more complex mechanical components such as motors and valves because of which regular maintenance is needed.They have less number of moving parts because of which less maintenance is needed.
They are very noisy as compared to Vapor absorption system.They are generally a quiet operating system.
They have high energy efficiency than vapor absorption system.They have low efficiency due to the use of low grade heat or waste heat.
The initial cost of investment or setup is low because generally standard materials are used.The initial setup cost is high as it involves complex components.
They can operate at a wider range of temperature as they are capable of achieving high pressure ratios.They work in a more restricted temperature.
Due to the use of flammable refrigerants such as ammonia, and other hydrocarbons they are quiet unsafe if not handled correctly.They are generally safe as they use water or other non toxic refrigerants.
They typically have high cooling capacity due to high pressure.As compared to a vapor compression cycle they have a low cooling capacity.

Maintenance and Troubleshooting of vapour absorption refrigeration systems

Like any refrigeration system, vapor absorption refrigeration systems require regular maintenance to ensure they are operating efficiently. This includes checking for leaks, changing filters, and inspecting the system for wear and tear.

If you experience any issues with your vapor absorption refrigeration system, it is important to troubleshoot the issue as soon as possible. Common issues include leaks, low refrigerant levels, and problems with the heat source.


In conclusion, vapor absorption refrigeration systems are an environmentally friendly and versatile alternative to traditional refrigeration systems. While they may not be as efficient as vapor compression refrigeration systems, they offer several advantages, including lower operating costs and the ability to use natural refrigerants.

When choosing a refrigeration system, it is important to consider your specific needs and the climate in which you live. If you are looking for an environmentally friendly and versatile option, a vapor absorption refrigeration system may be the right choice for you.

So, whether you are a homeowner looking to reduce your carbon footprint or an industrial facility searching for a more efficient refrigeration system, make sure to consider the benefits of a vapor absorption refrigeration system.

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