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Absorption Refrigeration Systems. Crystallization

Some of absorption chillers, which are notorious for �freezing’ or crystallization. The main mechanism of destruction is quite simple - the lithium bromide solution is so concentrated that crystals of lithium bromide form and connect the machine (as a rule, the heat exchanger section). The most common causes are:

Air leakage into the machine,
The low temperature of the condenser water, and
Electric power failures.

The first two are actually very similar because they both drive the consumption of heat to such an extent that crystallization may occur. Whether the leakage of air in the car or condenser water temperature is too low, the pressure of water vapor in the absorption of the evaporator should be lower than usual to make the necessary cooling. This causes the heat input to the machine to be higher for the increase of the concentration of the solution. Air leakage into the machine, you can control the design of the machine with a sealed integrity and regularly cleaning the machine with a vacuum pump.

Cold water condenser (combined with high load) you may also lead to the crystallization.

At decrease in the condenser water temperature can increase performance, this can cause quite a low temperature in the heat exchanger to crystallize concentrate. The sharp fall of the temperature of the condenser water can lead to the crystallization. For this reason, some of the early absorption chillers have been developed to produce a constant water temperature of the condenser. Modern absorption chillers special controls that limit the consumption of heat for the machine during these periods of low condenser water temperature.

Power failures can lead to the crystallization. Normal absorption disable be used to dilute the cycle, which reduces the concentration of the whole machine. This reduces the concentration of, the machine can cool down to ambient temperature without crystallization. However, if power is lost when the machine is under full load, and highly concentrated solution passes through the heat exchanger, crystallization may occur. The greater the power, the greater the likelihood of crystallization.

The main absorption chiller manufacturers now include device to minimize the possibility of crystallization. These devices sense of impending crystallization and shut the machine down after going through dilution cycle. These devices also prevent crystallization in the event of a power failure. A typical anti-crystallization unit consists of two main components: (i) the sensor in a concentrated solution of line at a point between the hub and the heat exchanger, and (ii) normally open, two-valve located on the line joining the concentrated solution of lines of supply of the refrigerant in the evaporator and sprays.

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