Enhanced Heat Transfer Technology Of Longitudinal Vortices Based On Field-Coordination Principle And Its Application

The high-efficiency energy conservation techniques, especially, the practical high-efficiency heat transfer enhancement techniques, have a bright application in many engineering fields, such as petroleum, petro-chemistry, energy, metallurgy, material, aerospace, electronics, and nuclear energy. The researches on the development and application of heat transfer enhancement techniques will create immense economic and social benefits. Based on the field-coordinated enhancement principle, the enhancement and optimization for convective heat transfer are studied by theoretical analysis, numerical simulation and experiments in this dissertation. According to the analytical, numerical and experimental results, new heat transfer enhancement techniques are developed and applied in engineering. Firstly, under the condition of constant viscous dissipation, the field coordination equation was induced for steady laminar convective heat transfer by the conditional variational principle based on the extremum principle of heat transport potential capacity dissipation. The numerical solution shows that the optimal velocity field for laminar convective heat transfer in tubes is multi-longitudinal vortex flow. Secondly, the relation between Nusselt number and the local time-averaged velocity and temperature fields of turbulent convection was theoretically induced, which expands the field-coordinated enhancement principle to turbulent convective heat transfer. It shows that both laminar and turbulent convective heat transfer can be enhanced by improving the coordination between the velocity and temperature fields. Consequently, a field coordinated enhancement method by longitudinal vortex flow for convective heat transfer enhancement in tubes is presented. The numerical analysis indicates that that the multi-longitudinal vortex flow in tubes can markedly enhance both the laminar and turbulent heat transfer with less additional increase of flow resistance.Tow multi-longitudinal vortex enhanced tubes, the alternating elliptical axis tube (AEA-tube) and the discrete double-inclined ribs tube (DDIR-tube), are invented according to the theoretical and numerical analysis. The experimental and numerical studies on the two enhanced tubes are performed. The strong multi-longitudinal vortex flow in the AEA-tube is induced by alternating change of the elliptical cross-section, and for the DDIR-tube, the strong multi-longitudinal vortex flow isinduced by the effect of the discrete double-inclined ribs. The existence of the multi-longitudinal vortices in tube improves the coordination between the velocity and heat flux fields for convective heat transfer, and remarkably enhances the heat transfer with less resistance increase. The performance analysis and comparison show that the two novel enhanced heat transfer tubes have excellent performance. After simulation and experiments for the new enhanced tubes, the processing technology and equipment for the novel enhanced tube were developed for industry manufacture, and the new heat exchangers with AEA-tubes are designed and manufactured, some novel heat exchangers have been successfully applied in the fields of architecture and energy, their energy conservation effect is remarkable.The enhancement techniques multi-longitudinal vortex induced by the primal surface change developed based on the field-coordinated enhancement principle will have broad application in heat exchangers.