Sunday, 17 January 2021 / Published in News

What is an absorption chiller?

Brief introduction of chiller

In a general definition, a chiller can be considered as a part of a more complex air conditioning system that, according to the laws of thermodynamics, changes its temperature by spending energy and performing processes on a particular material. This change for a particular substance, called a refrigerant, causes the refrigerant to reach different phases of gas or liquid. It is this continuous phase change that drives the chillers forward and makes the machine work properly. In fact, it can be said that the only focus of a chiller is to make changes to the refrigerant and change its phase continuously. The chiller is made of a set of fans, pumps, evaporator, compressor, condenser, holding tank, expansion valve, control panel, absorber, air conditioner and generator. Each of these can be different in different types of chillers. This means that a particular chiller can have its own combination of selected elements. It has an absorption chiller, an absorber, or an absorber, and a generator or heat exchanger, and a pump that is placed between the two. In fact, the case used especially in absorption chillers is these two devices, which are placed in compression chillers instead of compressors. Or, as is the case especially with compression chillers, their compressors. However, expansion valves, condensers and evaporators are common to all chillers.

What is an absorption chiller?

One of the most important types of chillers is absorption chillers. In this type of chiller, the basis of work on the shower is a factor called an absorber. This is what sets this chiller apart from other chillers.

In the operation of absorption chillers, chemical processes are used and for this reason, the energy consumption of this type of chillers is thermal energy. Therefore, if no electrical energy is available, the operation of absorption chillers will not be disrupted. Also, wasted heat energy can be used in projects to provide heat for this type of chillers.

In an absorption chiller, the movement cycle is such that refrigerant flows between the expansion valve, the evaporator, the absorber, the pump, the generator, and finally the condenser.

How does an absorption chiller work?

If we want to simply explain how absorption chillers work, we can draw a cycle.

In this cycle, all the elements mentioned in the previous section (from the expansion valve to the condenser) are present. The condenser and generator are at the top of the absorption chiller and the evaporator and absorber are at the bottom.

Initially, refrigerant, usually in the form of water, enters the evaporator and heats the ambient temperature to become a gas and raise its temperature. The result is a gas refrigerant; In this part, the ambient heat is absorbed by the evaporator. Then something must be done to get the gas refrigerant out of the evaporator. Salt is one of the best options for getting moisture, and lithium bromide are one of the best options for doing this in an absorption chiller.

Therefore, there is some concentrated lithium bromide in the absorber to combine with the water vapour leaving the evaporator and dilute it. In the next stage of this cycle, diluted lithium bromide enters the generator by a pump. This solution, which is directed to the generator, is in its thinnest state and is saturated; In the sense that it is no longer able to absorb. A generator is a heat exchanger that heats the refrigerant. The generator heats the solution, which is a combination of refrigerant and lithium bromide, and as a result, some of its water evaporates. In this way, a thicker solution is obtained than ammonia water. Finally, the water vapour separated from the ammonia-water solution enters the condenser to be distilled and converted into distilled water. This distilled water re-enters the expansion valve and then the evaporator.

What is the importance of lithium bromide in absorption chillers?

Lithium bromide is a salt that can absorb moisture and, in fact, water molecules. This adsorption merely dilutes the lithium bromide solution, which is itself a liquid at room temperature. This material is used in absorption chillers as an adsorbent.

What are the types of absorption chillers?

Absorption chillers are classified by three different criteria.

The first factor is their design mechanism, which divides absorption chillers into single-effect and double-effect groups.
The second criterion is the heat source intended for them, which can be hot water, hot water, hot air, steam, sun and direct flame.
The third criterion is based on the refrigerant and adsorbent determined for the chiller. In this regard, absorption chillers are divided into three types compatible with water and lithium refrigerants, compatible with ammonia and water refrigerants, and finally compatible with water and silica fume refrigerants.

Of course, it can be said that another classification is done based on the type of absorption chiller circuit current, which can be summarized in three types: parallel, series and inverse.

What is the meaning of a single effect and double-effect absorption chillers?

Single effect absorption chiller refers to chillers that have only one generator chamber. In contrast, the double effect absorption chiller concentrates its adsorbent solution in two stages. Once in a high-temperature generator and once in a low-temperature generator.

The high-temperature generator condenses the solution with the help of steam, or hot water or hot air, which enters from the main boiler, and the low-temperature generator increases the concentration of the solution with the help of refrigerant steam produced from the first operation in the generator. This reduces the heat required for the condenser distillation step, so in two-effect absorption chillers, the cooling tower capacity is less than that of the single-effect type.

Advantages of absorption chiller

The advantages of absorption chillers include: