Analysis of problems in the treatment of brine as a cryogen for cryogenic refrigerators

Because water as a brine can only be used when the cooling temperature is above 0 °C, and the brine solution has a lower solidification temperature, it can be used in medium and low temperature freezer to carry cold, usually calcium chloride. , magnesium chloride, sodium chloride aqueous solution.
[Analysis of problems when using brine as a cryogen for cryogenic refrigerators] Because water as a brine can only be used in applications where the brine temperature is above 0 °C, and brine solutions have lower solidification temperatures, so they can be used frequently. In the low-temperature freezer, the amount of cold carried is usually calcium chloride, magnesium chloride or sodium chloride aqueous solution. The freezing point of the brine depends on the concentration of the brine, the concentration increases, and the freezing point decreases. When the freezing point drops to the lowest point, if the concentration increases again, the freezing point increases. So, what problems should be paid attention to when brine is used as a cryogen for cryogenic refrigerators?




First, we must choose the concentration of brine reasonably

If the concentration of the brine is increased, the density of the brine will increase, and the power consumption of the pump that delivers the brine will increase. If the specific heat capacity of the brine is reduced, the flow of brine required to deliver a certain amount of refrigeration will increase, again increasing the power consumption of the pump. Therefore, the brine concentration should be selected based on the principle that the freezing point of the brine is lower than the lowest temperature that may occur in the brine system.




At present, the common selection method is to select the concentration of brine so that the freezing point is 5-8 ° C lower than the evaporation temperature of the cryogenic refrigerator (5 to 6 ° C if a water tank evaporator is used, and 6 to 6 when a shell and tube evaporator is used) 8 ° C). In this case, the sodium chloride solution is only used in a refrigeration system where the evaporation temperature is higher than -16 ° C, and the calcium chloride solution can be used in a refrigeration system having an evaporation temperature of not lower than -50 ° C.




Second, pay attention to the corrosion of brine solution to low temperature freezer and its pipeline

The corrosion of the brine by the brine is slowed down with the decrease of oxygen content in the brine. It is best to use a closed brine system to reduce contact with air. In addition, to reduce the corrosion, a certain amount of salt can be added to the brine solution. Corrosion inhibitor. After adding the corrosion inhibitor, the brine must have a slight pH (pH = 7 to 8.5). Note: Pay attention to toxicity when adding the above drugs.




3. The brine solution can absorb the moisture in the air during use, which leads to a decrease in its concentration. Especially in the open brine system, in order to prevent the temperature of the freezing point from rising due to the decrease of the concentration of the brine, the unit can be used regularly. The density of the brine is measured by a hydrometer. If the concentration is lowered, the amount of salt should be replenished in time to maintain the proper concentration.




Fourth, special reminder: sodium chloride and calcium chloride can not be mixed, precipitation occurs in the salt pool of Party B. Magnesium chloride aqueous solution can be used as a substitute for calcium chloride salt aqueous solution, but it is expensive and not widely used.

For more information on cryogenic refrigerators, please pay attention to the website of Shenzhen Dongyuejin chiller factory: http:// http://



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Low temperature freezer online mall: http://dyjok168.1688.com
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