Numerical Simulation Of Effects Of High Polymer On Flow And Heat Transfer Characteristics In Closed Chamber Cavity

In thermal convection flow of the fluid, especially when the fluids is turbulent flow,the flow situation is more complex. because of the fluid itself is complex,the thermal convection flow and heat transfer characteristics is also more complex. After adding a certain amount of polymer in the fluid, the polymer can change the viscoelastic properties for fluid, so the flow and heat transfer characteristics of the fluid can be changed. To find the effects of convective heat flow and heat transfer characteristics after adding polymers. In this paper, selected natural convection and Rayleigh-Benard(RB) thermal convection, and research and analysis respectively the impact of adding polymer.First of all, in order to verify the accurate of cross equation can represent the physical parameters of polymer adding, wo measured the curve of viscosity and shear rate for 200 ppm, 500 ppm, 1000 ppm polymer by the experiment;through data wo finded different concentration polymer relaxation time, zero shear viscosity and power-law,according to cross equation wo make the results of corresponds to the viscosity value with the experimental data of the same shear rate. the experimental viscosity and viscosity of the Cross equation are compared with the shear rate.Secondly, this article establis the geometric model of different thermal convection,wo maked the network independent validation for numerical models of different Ra respectively to ensure the feasibility and accuracy of the calculation of numerical simulation, after finding different the optimal grid.Wo make the simulated research in different medium and different Ra number fluid flow and heat transfer characteristics based on CFD simulation to study the effects for the thermal convection by velocity and temperature variation changing.Thirdly, in closed square cavity natural convection, as the Ra number increases, for any medium, the velcoity of fluid flow and heat transfer ability will increase and the increase is large amplitude when the number of Ra is large. And polymer adding had a great impact on natural convection in a square cavity for flow and heat transfer,polymer addition decreased the fluid flow resistance to increase the velcoity of the fluid,making hot and cold wall velocity boundary layer becomes thin.Numerical simulation results show that the Nusselt number decreased after the addition of polymer in hot wall,the wall temperature boundary layer thickening, fluid heat transfer weakens, according to the Nusselt number wo make the relationship of Ra and Nusselt number in the two different medium.Finally, for RB thermal convection, the effect of polymer addition on the fluid flow is consistent with the natural convection in the square cavity, the different is the natural convection of the RB is more complex. On the whole, the shear characteristics are themain effects when adding polymer, which makes the fluid shear thinning, the flow resistance decreases and the velcoity increases. At the same time, although the overall velcoity is increase, the fluid velocity value decreases in the direction of heat transfer,which inhibited the transfer of temperature and fluid heat transport capacity is reduced in a certain extent,he heat transfer decreases. Similarly, for the same Ra, the polymer addition makes the RB heat convection velcoity boundary layer thin and the temperature boundary layer thick.