The Vacuum Method Of Making Ice Slurry

Ice slurry, also called binary ice, is the mixture of water and ice particles with diameters less than1mm. It has characteristics of high energy storage density, easy transport, fast heat release, and no pollution. At present, it has been widely applied in life and large centralized cooling, medical and health, and other industries. Ice slurry has a large low temperature sensible heat and latent heat of phase change, it has become an important research topic for international researchers. In Japan and some European and American countries, ice slurry research has entered the stage of the industrial mass production and application stage. Our country for ice slurry research remains at the stage of theoretical study.There are many methods of making ice slurry, for example, the scraping method, the super-cooling method, the direct contact method and the vacuum spray method. Among these methods, the vacuum spray method is a kind of effective method, it According to the relationship of the boiling point of water and pressure, when pressure decreases, the boiling point also decreases.When using the tiny nozzle to atomize water, and reducing the pressure of environment, the boiling point of water is reduced, and the part of evaporates and absorbs heat, most of the rest water will condense into ice. The operation of the equipments of vacuum spray method is relatively simple, The system includes the water pump, the vacuum pump and the vacuum evaporation chamber where the water evaporates and condenses, and some other auxiliary equipments. The method of vacuum spray is convenient, highly efficient, the design requirements of various parts and the processing accuracy is not high. During the process, the vacuum is the key element.This article simply introduced the principle of this method, based on the principles of mass transfer and heat transfer, built the theoretical model and obtained a set of differential equations for the mass, velocity, temperature and the dropping distance of the droplet which was in vacuum condition, Simulations were performed by setting different initial conditions and vacuum conditions. Through the analysis and comparison of the calculated results, it was concluded that in a vacuum environment, freezing process of water droplets was related to the initial diameter and vacuum pressure. If the diameter and vacuum pressure was small, the time of water freeze was short. The result supplied the basis to design experiments and select experimental parameters.It should choose the spray nozzle which diameter is smaller. At the same time, the pressure of vacuum chamber should kept low.Based on the analysis, the general layout of experiment of vacuum method was constructed, a water supply system which can be easily controlled was built, a vacuum pot was designed according to the compressive conditions and the reasonable installation, designed a exchanger for condensing water according to the amount of water vapor which calculated, the proper vacuum gauge and the vacuum pump for maintaining vacuum were selected, the appropriate subtle nozzle used to spray droplets and the thermocouple for measuring and monitoring the temperature variation of the experiments, visual glass windows were used to watch the experimental progress, the experimental data were recorded. The experiment results showed that at the same conditions the time required for certain volume of water to become ice completely had nothing to do with the initial temperature of water, because the sensible heat of water is very small compared with the latent heat. When supply pressure of water was different and other conditions were the same, the relationship between ice packing factor contained in ice slurry and the water supply pressure was inversed; if water supply pressure was smaller, the ice packing factor of ice slurry was higher. When the other conditions were the same, the relationship between ice packing factor of ice slurry and the initial vacuum pressure was inversed; if the initial vacuum pressure was smaller, the ice packing factor of ice slurry was higher. By adding a certain amount of glycol solution, the better mobility ice slurry can be obtained, with more appropriate ice packing factor.