| The cold storage technology can realize the peak shifting and valley filling of power.In the trough of power grid at night,the refrigerator store the cooling capacity by cold storage materials,and then provide cooling to meet the peak of power grid in the daytime.So cold storage technology has both economic and social benefits.The choice of cold storage materials is very important for the efficient operation of cold storage air conditioning,which is directly related to the efficiency of storage and transportation.Because of its large cold storage density and fine fluidity,functional phase change slurry has become a research hotspot.Firstly,in this thesis,the phase diagram and crystallization law of urea aqueous solution were studied,and the crystallization model of binary eutectic aqueous solution in the solid-liquid two-phase region was constructed.It is pointed out that there is a paste liquid film between the crystal layer and the cold surface in this temperature region,which shows the porous structure of solid-liquid mixture.The flow scouring experiment setup of crystal layer was built,and the adhesion of ice layer with different velocity and supercooling was explored.It was found that in the solid-liquid two-phase region,the adhesion of ice layer was small,and it could be scoured away by fluid with the appropriate velocity and supercooling.Secondly,the experimental setup for ice slurry generation and flow characteristics was built to study the physical properties of ice slurry,such as its preparation,particle size and kinematic viscosity.Then we explored the flow characteristics of ice slurry with different diameters,Reynolds numbers and ice packing fraction.In the case of thin tube and large Reynolds number,the ice slurry was closer to Newtonian fluid.However,the ice slurry with large IPF deviates from Newtonian fluid.The power-law model was used to analyze the flow characteristics of ice slurry.It was found that the flow characteristic index n’ decreases with the increase of IPF,while the consistency coefficient K’ is positively correlated with IPF.With the certain IPF,n’ decreases slightly with the increase of tube diameter,while K’increases gradually with it.In order to better describe the complex flow characteristics of non-Newtonian power-law model fluid,the modified Reynolds number was introduced to quantitatively analyze the slurry.By exploring the relationship between the modified Reynolds number and Fanning friction coefficient,it was found that with the increase of IPF,the range of transition Reynolds number in 4 mm,6 mm and 8mm tubes were 2500-3000,1600-2300 and 1500-1900,respectively.Finally,the physical properties of urea slurry were study.The supercooling of urea slurry is only 0.7°C,lower than that of ice slurry and hydrate slurry.However,the phenomenon of static stratification of urea slurry is obvious,and agitation is needed during generation.For the flow pressure drop of slurry in horizontal tube,urea slurry > TBAB hydrate slurry > ice slurry,but the difference is not significant.The density of urea solution decreased slightly with the increase of temperature and increased significantly with the increase of concentration.The dynamic viscosity of urea solution is higher than that of water,but it is still at a small level.The apparent viscosity of urea slurry is larger than that of ice slurry,and the maximum value is about 120 times of urea solution.The effective latent heat of urea solution is 223.2k J/kg～213.7 k J/kg with concentration range of 43%～48%,which is higher than that of TBAB hydrate slurry.The corresponding temperature range can be applied to cool storage air conditioning. |
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