The Study Of Ice Crystal Formation Mechanism In Supercooling Method Of Ice Slurry Making Technology

The phenomenon of supercooling exists in cold water is taken advantage to make ice into ice-water mixture which is known as "ice slurry", the "ice slurry" has good fluidity and storage density. It has broad application prospects in the area of air-conditioned storage、mine cooling、frozen food、a large amount of concrete pre-cooling. At present, supercooling method of ice slurry making technology is technically immature. Therefore, in-depth study of ice crystal formation and growth mechanism of ice slurry making technology, not only has important practical applications, but also has certain academic significance. The main contents and results of this study are as follows:The hydrogen bond theory of ice、the thermodynamics of supercooling freezing cold water、phase transformation driving force of dynamics and supercooling ice crystal growth theory is overview and analysis.The solution was stirred and supercooling method of ice slurry making experimental device is designed and built. This experimental device has the advantage of these:the experimental parts are easy to replace, regulate working conditions and control conditions are easy. The device can be used to systematic experimental study of the influence of relevant factors for ice crystal formation and growth of aqueous systems.Under certain flow and temperature conditions, the temperature distribution within the vessel was researched, the cyclic freezing solution and supercooling cold freezing process cooling characteristics were analyzed. The influences of some operating parameters on the degree of supercooling and ice slurry characteristics were researched experimentally. The experimental results show that:when use tap water, ice slurry in supercooling making method is normal. when choose deionized water, the cyclic freezing solution happened near the freezing point, the purpose of the ice slurry making can not achieve the experimental requirements. The agitation speed effects significantly on the phenomenon of supercooling. When the refrigerant temperature is reduced, the supercooling degree significantly increases at first, The supercooling degree reaches the maximum value 4.5℃ at the refrigerant temperature of -12℃, then does not change obviously. Volume of the container changes from 250ml to 350ml process, the supercooling degree does not change obviousl. With the volume expanded to 400ml, the supercooling degree significantly reduced 1.275℃. Container materials have different degrees of impact on the supercooling degree, the polyvinyl fluoride cup supercooling degree is minimum and away from other materials than 2℃, the supercooling degree of stainless steel cup、enamel cup and glass cup are close, only 0.1-0.2℃ gap.For the experimental study of the ice crystals formation and growth control, to study accelerate or slow down the ice formation and growth rate by adding various additives. The ice crystals become fine and smooth when the ethylene glycol is added in the water. In low-density areas(concentration of ethylene glycol<6%), supercooling degree Increases slightly with the concentration of ethylene glycol. In high-density areas(concentration of ethylene glycol>6%), when the concentration of ethylene glycol increases, the supercooling degree decreases sharply. When NaCl concentration in the range of less than 1.5%, the supercooling degree does not change obvious. When the concentration is greater than 1.5% to 2%, the supercooling degree reaches the maximum. When the concentration of NH4Cl is greater than 1% to 1.5%, the supercooling degree reaches the maximum, then the supercooling degree declined. Compare with NaCl, the ice crystals become smooth and have good transport properties when the NH4C1 is added in the water. After the nucleating agents were added, the supercooling degree decrease sharply, the time of remove supercooling is in advance. Compared with iron sulfate and silica, borax nucleation is worse, but forming ice crystals have good characteristics. After the surfactant were added, the supercooling degree does not change obviously. Ice crystals become smooth and have good transport properties, but made a small amount of ice crystals, the amount of bubble is greater inside, cyclic freezing℃ probability also increased significantly. After adding nanoparticles, Whether adding magnesium oxide or zinc oxide nanoparticles is added in the water, the supercooling degree decreases sharply, less than 3℃. For both of these nanoparticles,0.1% nanoparticle nucleation is best. When the nanoparticle concentration increased, the nucleation effect is worse.