Study On The Ice Slurry Produced By Spiral Scraping

Ice slurry,also could be called binary ice or pumpable ice,is a kind of solid-liquid two-phase mixed solution and has good flowability.As a new good kind of coolant for cold storage and storage medium,ice slurry has been widely used in the fields of building district cooling,food processing preservation,medical treatment,industrial cooling and some other industries abroad.Along with the sustained and rapid development of economy in our country,the contradiction between supply and demand of electric power resources has become increasingly prominent.The adjustment of power consumption structure is urgently required.All of this would make the application and popularization of ice slurry in refrigeration system in our country become imperative,and make the study on ice slurry technology such as production,development,and improvement become research focus.The main advantages and disadvantages of the current six international method of ice slurry producting technology are analysed in this thesis.In order to improve the current method and apparatus,a new dynamic ice slurry making method named spiral scraping ice slurry generation technology is developed.The structure of the apparatus is explained,and the performance of the new generation apparatus and the ice slurry as product are analyzed both theoretically and experimentally.The main research concent and conclusion are as follow:(1)By using crystallization kinetics and heat transfer theory knowledge,the process of ice crystals generating in the generation is separately analyzed from the angle of microcosmic and macroscopic.With certain simplifications,the equation of ice crystal growth rate on the inner wall of the spiral scraping generation and the relation between the ice thickness on the inner wall changing with freezing time are derived.The result shows the ice thickness ? on the inner wall would increase approximately in a line with the freezing time t,when the scraper scraping in apparatus is neglected.(2)Demonstrated by practiced,the new dynamic ice slurry making method is feasible.The apparatus runs steadily and can be easily operated.The ice slurry as product has good flowability,with the maximum ice packing factor(IPF)of 13.684%and maximum ice production of 3.590 kg/h.The ice crystal particles in ice slurry distribute uniformly,and generally present as strip or oblate,with an average area of between 10-9 m2 and 10-8m2.(3)In research of the apparatus factors' influence on the ice slurry as product and the new spiral scraping apparatus' performance,the experimental results show the ice packing factor of the ice slurry would increase over time firstly and reach the peak,after which it would fluctuate slightly and then gradually decrease,finally it would keep stable at a constant value.Decreasing the flow of ice-making solution,reducing the initial inlet temperature of the coolant or the ice-making solution would shorten the initiation time of the apparatus producing ice slurry and increase the ice packing factor of the product.While increasing the flow of ice-making solution or accelerating the rotary speed of spiral slicker would make the ice crystal particles in the ice slurry smaller.The outlet temperature of ice slurry in the apparatus would change with different additives and different concentrations in the solution,which is numerically equal to the end temperature of similar solution's supercooling degree.(4)In research of the kinds of the solution additives and solution concentrations'influence on the ice slurry as product and the apparatus' performance,the results show:as to the alcohol or salt aqueous solution,increasing concentration of the solution would reduce the outlet temperature of ice slurry,extend the initiation time of apparatus producing ice slurry and increase the ice packing factor of ice slurry.While as to the nano-particle additive or surfactant aqueous solution,the changing of the solution concentration has no obviously effect on the outlet temperature of ice slurry,etc.And the changing trend between the size of the ice crystal particles in ice slurry and solution concentration would be influenced by the kinds of additives and specific concentration.