Slit Geometry Effect On The Flow Stability And Heat Transfer Process Of Fluid In The Annulus

Taylor–Couette is widely occurs in rotor system of rotating machinery such as electric motor, the shaft sealing instrument of heat pumps,the outer wall of rotating heat pipe, transmission devices of NC machine tool, etc. The study on the heat transfer process of Taylor-Couette flow has an important effect on the improvement of the mechanical performance and operation stability. To study the slit dimensions effect on the flow field and its heat transfer process and the main contents are as following:In this paper, Taylor-Couette flow were investigated by PIV Technology when slit number is six with or without temperature gradient. The influence of slit on the flow field and heat transfer characteristics of Taylor-Couette flow in the annular gap are obtained. The Taylor vortex flow in the annulus gap was studied by numerical simulation, the reliability of the calculation result was verified by PIV experiment.In order to study the effect of slit dimensions on the flow field and its heat transfer process, we mainly study the three important flow patterns of Taylor vortex, wavy vortex and turbulent Taylor vortex. The research work is carried out with or without temperature gradient. The main contributions are as follows:A preliminary study on the model of different slit dimensions was found that the heat flux of the model with 0.75 depth to width ratio has a maximum heat flux. When the depth to width ratio is larger than 0.75, the heat transfer ability of the fluid was not strengthened obviously as the further increasing of slit depth. Taylor-Couette flow affected by slit dimensions when slit number is nine with or without temperature gradient.1) Under isothermal conditions: changing the depth of slits has no influence on the axial dimension of Taylor vortex at Taylor vortex state,but it can increase the radial velocity of the center of the annulus gap; With the increase of the slit depth, both amplitude of wavy vortex flow and wavelength will increase; The fluid near the the inner wall of the model with 0.75 depth to width ratio has a maximum turbulent intensity at turbulent Taylor vortex state.2) Under the condition of heat transfer: at Taylor vortex state the model with 0.75 depth to width ratio has a maximum Nusselt number of the inner cylindrical wall; With the increase of depth to width ratio, the heat transfer performance of the fluid in the annulus is not enhanced significantly; Increasing the temperature gradient between inner wall and outer wall makes the amplitude of the wave vortex decrease along the axial direction and the vibration frequency is kept constant at wavy vortex state; At turbulent Taylor vortex state, the model with 0.75 depth to width ratio has maximum turbulence intensity and heat flux of outer cylinder wall; At Taylor vortex state and wavy vortex state, the temperature gradient between inner wall and outer wall is higher, the stronger inhibitory effect of flow transition.3) The heat transfer analysis of the model with 0.75 depth to width ratio was performed. Considering the heat transfer of different temperature and rotating speed at the same time, the solution of the linear equations which is suitable for the linearized expression of Nusselt number: 9136.00.8633?0283.0 PrRNu e)()(.Among four different models in this study, the model with 0.75 depth to width ratio has the best heat transfer ability, and in a certain range the heat exchange between fluid and wall can be strengthened as the increasing of the slit depth. It makes sense to improve the heat dissipation performance of rotating machinery.