Brines are used as coolants, i.e. solutions of various salts in water. The most common are aqueous solutions of sodium chloride NaCl and calcium chloride CaCl2. In refrigeration units of refrigerated cars, a solution of calcium chloride is used. The properties of the brine are determined by its concentration, that is, the content of dissolved salt as a percentage per unit mass of brine. Sometimes the concentration is measured by density (in g/cm3).
For each brine, there is one concentration value corresponding to its cryohydrate state. At this concentration, the brine freezes in the form of a homogeneous cryohydrate mixture, and the temperature of its measurement is the lowest. So, the cryohydrate freezing point for calcium chloride brine corresponds to -55 ° C (for 100 hours of water there is 42.5 hours of salt). With an increase or decrease in the concentration corresponding to the cryohydrate point, the temperature of the onset of solidification of the brine rises. At the same time, brine of increased concentration becomes more viscous and more power is required to pump it through pipes.
