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23 August 2021
The most important information about ABSORPTION refrigeration

Together with cogeneration, the demand for absorption refrigeration is increasing. It works completely differently than traditional compressor refrigeration. Below is the most important information you should know about it:

1. How absorption refrigeration works (very simplified principle)

The hot water (from the heat source) heats the diluted bromine lithium until the refrigerant contained in it begins to evaporate. The lithium bromine solution thickens. This solution is then fed to the absorber.

The refrigerant vapors reach the condenser where they condense on the surface of the cooling water pipeline. This water is cooled in the tower. The condensed refrigerant is fed to the evaporator.

The pressure in the evaporator is close to vacuum, so the refrigerant in it evaporates, cooling the water (which is then fed to, for example, air conditioning). The gas obtained in this way is fed to the Absorber.

The refrigerant vapors are condensed by the cooling water and absorbed by the concentrated lithium bromine solution. The solution is then fed into the generator and the process repeats.

  • The ability to maintain the required vacuum inside the chiller is a key parameter. Most chillers lose their vacuum due to imprecise workmanship and must have a factory fitted vacuum pump. The best devices, such as YAZAKI, thanks to very precise workmanship, maintain the vacuum and do not require a factory vacuum pump.

  • The air entering the chiller (together with impurities and water vapor) causes a gradual degradation of the lithium bromine charge. YAZAKI chillers, thanks to their tightness, do not require periodic replacement of the components throughout their lifetime.

  • The noise of the chiller is negligible

  • The 430 kW chiller will have dimensions of approximately 1.7 x 3.7 x 2.2 m and a weight of 5.7 tons in operating mode

  • SZE sp. z o.o. offers absorption chillers with a cooling capacity between 17.6 and 450 kW.

2. What is an absorption chiller useful for?

Bromine lithium absorption refrigeration can produce chilled water down to 5°C. This water can be used for air conditioning or technology.

There are absorption ammonia chillers that can reach lower temperatures, but due to the mode of operation, they are difficult to use, for example, for storing frozen food.

3. What is needed to be able to use an absorption chiller

The most important thing is a stable source of heat. Stable in terms of its amount and temperature.

The required temperature is between 70 and 95°C

The heat source can be:

  • Cogeneration
  • Air compressors
  • Cooling of machines and devices (e.g. metallurgical furnaces)
  • E.t.c.

4. Energy consumption and efficiency (COP)

The main advantage of absorption chillers is the conversion of heat into cold almost without electricity consumption – “for free” (almost).

An absorption chiller with a cooling capacity of 430 kW consumes 630W of electricity. However, the energy consumption of the cooling tower fan and pumps must be taken into account. Together, the entire set with the above-mentioned power will consume about 20 kW of electricity.

The efficiency of an absorption chiller is determined by the COP coefficient, which is described by the formula below:

COP = cooling power obtained / heat power delivered

It is usually between 0.5 and 0.8 and its value is greatly influenced by the temperature of hot and cold water.

5. Cooling tower

  • Open cooling towers are the most common. This means that the cooling water is in direct contact with the air.

  • The power of the cooling tower is defined primarily by the wet bulb parameter for which we select it. For each region in Poland, it should be selected individually, but most often it is between 21 and 23C. The higher the temp, the better the parameters, but the bigger and more expensive the tower.

  • Another important parameter is the purity of the water for which it is selected and the resulting filling of the tower.

  • Typical towers have a volume between 64 and 51 dB. However, there is the option of further muting.

  • The required amount of water fed to the tower, and thus the power of the pumps and the diameter of the pipelines, result from the chiller balance.

  • Well equipped towers have removable inspection panels, anti-freeze heaters and serviceable nozzles matched to the required flow, cleanliness.

  • The tower needs to be replenished with treated water. Treatment should be selected for the specific composition of water at the customer.

  • The 430 kW chiller tower will measure 2.4 x 3.7 x 3.6 m and weigh 3.9 tons in operation.