Numerical Simulation Study On Nanofluid Rayleigh-Benard Natural Convection Of Flow And Heat Transfer

Nanofluid has good thermal conductivity, which is widely used in daily life and industry. Since the concept of nanofluid, the scholars began to study it, the research content includes: nanofluid stability, physical properties, heat transfer characteristics, strengthening heat transfer mechanism and so on. However, the study of natural convection is the beginning, and the research results of nanofluid natural convection and forced convection are very different. No theory can explain the cause of this difference. In this paper, Fluent software is used to simulate the flow and heat transfer of Rayleigh-Benard natural convection in a rectangular cavity.First, the rectangular cavity is filled with fluid and formate of stable pairs of vortices under different Rayleigh numbers; A flow function contour is used to indicate the formation of convection; Rayleigh-Benard natural convection is the result of the action of gravity, fluid viscous force and buoyancy; When the central point of the rectangular cavity is the maximum and not changed, the flow is stable, and the vortex flow of Rayleigh-Benard natural convection is stable and spontaneous and the direction of the flow is anti-clockwise and clockwise.Secondly, the multi phase flow model is used to simulate the nanofluid in the rectangular cavity, The simulated values are compared with the reference values and the empirical formulas, and the error is within the allowable range. Fitting the data in a certain range, the correctness of the model is proved.Finally, on the basis of the correct model, the nanofluid in the rectangular cavity is simulated. To obtain the following results: Changes in the Nusselt number is nonlinear in the process of formation; Comparison of heat transfer between nanofluid and water: When the Rayleigh number is less than 6×106, the heat exchange of water is better than nanofluid, when the Rayleigh number is greater than 6×106, the heat transfer of the nanofluid is better than water. Small particle size of the nanoparticle fluid heat transfer effect is better. Base fluid physical parameters of comprehensive comparison is measure for the basis of the effect of heat, and forced convection heat transfer only compare the thermal conductivity of the base fluid has great difference. In natural convection and forced convection, the addition of metal particles is better than that of metal oxide particles.