Investigation Of Isothermal Storage And Flow Characteristics Of Ice Slurry Within Non-uniform Ice Particles

Building energy efficiency is considered a key area for China to achieve its carbon emission reduction target before 2030,and it is imperative to accelerate the development of ultra-low-energy green building technology.As an advanced strategy of building energy supply,regional cooling is an important index to measure the energy conservation of the system.In recent years,it has become an important measure to improve the efficiency of cooling capacity transmission in dynamic cooling storage system and distribution network by replacing traditional chilled water with high-load ice slurry and providing cooling capacity users with phase change full heat instead of temperature difference sensible heat.However,how to transport the ice slurry with the characteristics of two-phase flow,variable particle size and phase transition safely and efficiently from the preparation storage end to the target building is still facing a huge challenge.For this reason,the isothermal storage and flow characteristics of non-uniform size ice slurry were studied in this paper.Firstly,considering the phenomena of growth,coalescence and fracture of ice particles,the isothermal storage process of ice slurry was studied by means of experimental testing.Based on the observation and recording of the geometric morphology of the ice particles obtained by microscope,statistical analysis was conducted by using statistical methods to explore the changing rules of the morphology of ice particles and the equivalent diameter of ice particles in the isothermal stored process with time.Then,the population balance theory is introduced to establish a prediction model of ice particle size distribution in isothermal stored process,and the influence mechanism of factors such as storage time,fluid loading concentration and ice content on ice particle size evolution in isothermal stored process is explained.And then Euler-Euler coupled two-phase flow model and population balance model,the particle size of ice slurry pipeline such as isothermal flow mathematic model,further analysis of ice slurry isothermal flow velocity field and concentration field,particle field,stress field of flow velocity,fluid concentration,ice content,the response of the core factors such as the initial particle size change rule.At the same time,with some experimental tests and literature experiments to complete the mathematical model experimental verification and correction.The research results show that in the process of ice slurry isothermal storage,ice particles present particles grew up with the decrease of particles two reverse granularity characteristics,with the increase of storage time,ice particles form from the polygon to ellipsoidal and spherical,gather more effects and rupture,ice particle size increases gradually,and the variance of ice particle size presented a certain growth trend,but the growth rate of leveling off.When the concentration of liquid solution increases,the growth rate of ice particles increases with the increase of solution viscosity.When the concentration of liquid solution increases by 10%,the increase range of particle size is about 0.18 mm.When the ice content rate of the ice slurry increases,the growth rate of the ice particles increases with the intensification of the polymerization process.For every 10% increase in the ice content rate of the ice slurry,the particle size increases by about 0.15 mm.During the isothermal flow of the ice slurry,due to the density difference between the liquid carrier and the ice particles,the ice particles along the cross section of the pipeline gather at the top of the pipeline,with a high concentration of ice particles at the top and a low concentration at the bottom of the pipeline.The distribution of ice particle size along the pipeline section is not uniform,but it is different from the distribution of ice particle concentration.The particle size of ice particles at the top and bottom of the pipeline is larger,while the particle size at the middle position is smaller,and the particle size of ice particles at the top of the pipeline is larger than that at the bottom of the pipeline.At the same time,along the flow direction of the pipeline,the size of the ice particles gradually increased.On the whole,when the fluid flow rate,ice content and liquid concentration increase,the uniformity of the distribution of ice particles in the pipeline becomes better,and the increase of the average particle size becomes more obvious in the flow process.Compared with the distribution of ice particle size,the distribution of pipeline pressure drop is more significantly affected by the change of fluid velocity and ice content.