Research On The Characteristics Of Fluid Flow And Heat Transfer In Rotating Curvilinear Pipes

Rotating pipes system are often encountered in the rotary machinery of engineering applications. With the popularity of rotary machinery in industry, the characteristics of the fluid flow and heat transfer in the controlling pipe system, the transporting pipe system, and the cooling pipe system are the main factors to improve the efficiencies of the rotary machinery. Meanwhile, When a man is in the aerocraft with a high rotating speed or in the rotating machine for training, the flow in the blood vessel of body will change evidently and so the study on the flow in the blood vessel also becomes the important research field in the aerial-physiology. This study is signality in theory and has a broad application future. Consequently, fluid flow and heat transfer in rotating pipes has become one of the urgent problems in engineering and one of the challenging research fields in fluid mechanics.The detailed review of the research on the flow and heat transfer in the curvilinear pipes from the last century are firstly made in this dissertation. Based on the review, the fluid flow and heat transfer in the curved circular and rectangular pipes have been researched by employing perturbation method and numerical simulation with a physical model under the rotational orthogonal curvilinear coordinate in a rotating curvilinear pipe with multi-parameters. We firstly analyzed the fully developed fluid flow and heat transfer, mixed convection heat transfer, the development of flow and heat transfer in the inlet in different cross section (circular, elliptical, annular and rectangular crossection). The variations of the secondary flow, axial velocity, distribution of temperature, the friction force on the wall, the ratio of friction factor as well as the Nusselt number with different dimensionless parameters had been examined in detailed. The bifurcation phenomena in a certain condition had been obtained. And comparisons are made between the results of this study and published experiment and numerical results. All of the results are all in good agreement. Some new and interesting conclusions are obtained as follows:There exists evident difference on the flow behaviors and heat transfer between rotating curvilinear pipe and the stationary curvilinear. When the rotation has the same direction with the axial velocity, the effect of rotation enforces the intensity of secondary flow and the heat convection, the friction factor and the Nusselt number increases as F increase; When the rotation has the opposite direction with the axial velocity, the flow structure becomes more complicated,for F=1.2, the complicated structure of secondary flow generates, the friction facior and Nusselt number almost has the same value of stationary straight pipe. The location of maximum of axial velocity depends on F . The effect of Pr on distribution of temperature is evidently. For different F , the effect of curvature and torsion on the flow structure, temperature distribution, the friction factor and Nusselt number. When the dimensionless governing parameters exceed some critical value, the bifurcation phenomena in the rotation pipe with rectangular and elliptical will appear and the flow structure becomes more complicated. When the pipe is heated or cooled, the centrifugal-type buoyancy force has the obvious effect on the flowstructure and temperature distributions, when the Ra increases or decreases to a critical valuefor a given F , the buoyancy force instability also can be found. At the entrance of the rotating curvilinear pipe, both the development of flow structure and temperature distribution depend on F and the characteristic quantities of flow and heat transfer change obviously. Comparing with the stationary straight pipe, the entry length becomes larger.