Numeric Simulations Of The Turbulenceflows In Heat Exchanger Tube With Miniature Hydraulic Turbine

Miniature Hydraulic Turbine (MHT) in Heat Exchanger Tube can realize fouling prevention on line and enhance heat transfer. Flows in the pipe with MHT are very complicated three dimensional ones and have helical shapes. The numerical simulation is of great help to understand the characteristics of flow field in the heat exchanger tube. Rotating Frames of Reference (RFR) are useful for rotating fluid machinery applications, so the governing equations are built up with it. Turbulence model is introduced to form close equations. Then the influence of RFR on the turbulence model is considered curtly. In this thesis, a fully-implicit finite-volume numerical algorithm is developed to solve the time-dependent Navier-Strokes equations.The first step for numerical simulation is to create the flow-field geometry with Pro-Wildfire. Next, import the geometry into ICEM-CFD for mesh. In this meshing software, a high quality of meshing grid can be got by using smoothing method. CFX is a general purpose Computational Fluid Dynamics (CFD) code, combining an advanced solver with powerful pre and post-processing capabilities. Setting up a problem for CFD has three distinct steps - geometry creation or import, mesh creation and physical problem set-up. At the heart of CFX-5 is the CFD solver, which brings together a range of technologies to deliver high performance CFD. CFX-Post is a powerful graphical and quantitative postprocessing tool that allows users to quickly extract useful information from CFX-5.The numerical results will be checked up in the forth chapter. Firstly, it is practical to analysis experimental data which can be used for comparison with the numerical results. From experimental data the MHT shows greatperformance in heat enhancement and fouling resistance. Secondly, the way to calculate the angular velocity is introduced, which is helpful for experiment which needs more money and time. Finally, with contour plot in CFX-Post, the turbulent flows are shown clearly, and by using function calculator the axial velocity and rotational velocity are got exactly, which can be used for theoretical analysis. From the contour plot, the second flow can be seen near the impeller, and the turbulent flows take up most of the flow field. It means MHT works effectively.The influences on numerical results are described in the fifth chapter. It mainly includes boundary conditions, turbulence model, the quality meshing grid, the flow field. For these considerations, some practical measures are come up with, which may improve the numerical precision and accumulate numerical simulation experience.