Effects Of Dynamic Load On Natural Convection Heat Transfer Of Refrigerants With Phase-Change-Material Microcapsulate

As a new type of functional fluid,which can effectively enhance convective heat transfer,the microencapsulated phase change material slurry has a higher applied value in industrial production and daily life.The natural convection of the microencapsulated phase change material slurry and the effect of dynamic load on it have been studied in this thesis.First,a natural convection model for two-dimensional enclosure was established and a numerical simulation was performed with Fluent.The predicting data were compared with the references,and the error is within 0.5%.Therefore,the correctness of the model and calculation method were verified.Secondly,a natural convection model of the slurry containing phase-change microcapsules was developed based on the equivalent specific heat.The enhancement of phase change microcapsule on convective heat transfer was analyzed with this model.Under the same Rayleigh number,the temperature distribution of the phase-change microcapsule slurry with different volume fraction of phase-change microcapsules is basically the same.With an increase in the volume fraction of the phase-change microcapsules in slurry,the viscosity of the fluid increases,and the flow rate decreases.The heat transfer enhancement increases with the increase of the volume fraction of microcapsules.As the volume fraction of microcapsules reaches 0.15,the enhancement is increased by around 25%.Under the same volume fraction,the convective heattransfer in the enclosure increases with the increase of Rayleigh number.A natural convection model of phase-change microcapsules slurry in three-dimensional cavity was then established based on the equivalent specific heat.The effects of the body force caused by the dynamic load on several directions on the convective heat transfer performance of the slurry was studied respectively.In a direction perpendicular to the temperature gradient and gravity,the effect of dynamic load on convective heat transfer mainly depends on its magnitude.In a direction parallel to the temperature gradient,the effect of dynamic load on the convective heat transfer strongly depends on its direction.As the direction of the body force is the same with that of the temperature gradient,the heat transfer will be weakened,otherwise enhanced.In the vertical direction,the influence of dynamic load is related to the relative magnitude and direction of dynamic load and gravity.The bigger the magnitude,the obvious the effect.For the dynamic loads in YZ section,the influence of dynamic load angle on heat transfer enhancement was analyzed,and a change range of the angle in which the natural convective heat transfer was enhanced has been obtained.The natural convective heat transfer characteristics of the phase-change microcapsules slurry in the side-heated cavity were simulated.The effects of volume fraction,Rayleigh number and dynamic load on its heat transfer performance were investigated in the thesis,which might supply reference for relevant researches and applications.