| According to the current energy crisis, and the concept of low carbon, based on theedge ray principle, a new solar collector named selective solar tunnel (SST) is designed inthis thesis. The selective solar tunnel with its particular geometric features can absorb thesunlight according to the different solar angle so as to heat house in winter and avoidheating in summer.After SST absorbs solar radiation then changes into heat energy, part of the energyflows to the indoor by heat conduction then convection under the working condition ofwinter. The other part of the energy flows to the outdoor by convection then heatconduction then convection. The outdoor heat energy transfers to SST by convection underthe condition of Summer, then repasses inside the SST by a series of thermal conductivity,convective heat transfer and thermal transfer heat to indoor wall of the SST. Finally ittransfers to the indoor environment by convection. In this paper, by establishing amathematical model of SST and using the normal working condition of summer in Xuzhouarea as an example, to use advanced finite element analysis software of ANSYS andFLUENT to simulate the internal fluid temperature field and velocity field of SST. Finallyto obtain characteristics of internal flow field and temperature field of SST and analysis ofthe thermal fluid flow characteristics of SST.In order to verify the accuracy of the theoretical simulation results, the SST system testbench was designed and built by oneself. Both have good consistency by testing SSTinternal air temperature field and comparing with the results of numerical simulation.Based on the previous analysis of thermal fluid characteristics of SST, a large amountof numerical analysis and calculation were carried on by changing the outdoor wind speedand temperature. It is found that the increase of wind speed can reduce outdoorenergy-saving efficiency of SST in Summer, but its influence mainly concentrates during0to4m/s, with maximum reduction of about9.63%; Outdoor temperature increase willcause internal air convection and heat transfer enhancement of SST. Heat flux density ofouter wall of SST is in a straight line growth with temperature, which weakens theenergy-saving effect of SST in summer. By changing the distance of transparent cover plateand absorption plate, the relationship is analyzed between heat flux and the characteristiclength and it is found that the heat flux density of SST shows the decreasing trend ofvelocity with the increase of characteristic length, which is stable when the distance oftransparent cover board and absorption plate is0.09m; And it is concluded that the choice of the most optimal characteristic length of in winter or summer should be the combinationwith the characteristics of the decreasing efficiency in winter and the owner needs. Finallyaccording to the result of numerical simulation, a series of numbers were got such as Nu Bi,and Ra. By using Tabecure3D software to fit out thermal fluid criterion equation under theworking condition of Summer of SST, which provides people with the convenience forpeople to study the law of fluid flow in the closed cavity body, the structure optimizationdesign and the calculation of energy-saving efficiency of SST, and it has importantreference value for heat transfer characteristics of the flat plate collector research. |
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