Numerical Simulation And Experimental Study Of Heat Transfer And Pressure Loss In The Dimpled Tube

With the development of technology and short of energy, the technology of heattransfer enhancement is always the keystone of research. Compared to other heattransfer enhancement approaches, the dimple heat transfer enhancement technologycould improve heat transfer rates without a significant increase in pressure drop, so itwas extensively used in industry. Many scholars have proved that the dimple surfacecan strengthen the heat transfer and pressure drop by experiments and numericalsimulation. The generation of the dimple leads to the protrusion on the other side of thetube, the protrusion could also improve heat transfer effectively, but related research islacking. In this thesis, heat transfer and flow in turbulence condition are simulated byusing the dimpled tube as geometric structure and the FLUENT software. At the sametime, the paper validates the reliability of the simulative results through theexperimental study and comparison of experimental data and simulation results.First of all, present thesis sets up the geometric model and the physical model ofdimpled tubes. In the math model RNG k-ε turbulent model was employed, andSIMPLE algorithm was applied to resolve the pressure-velocity coupling. This modelwas checked up by the experimental data in other people’s paper.Through observing the flow field and the temperature field inside the dimpledtube, and analyzing the heat transfer performance and flow resistance in local and theglobal-averaged heat transfer, the mechanism and reasons of heat transfer enhancementresulted from protrusion were exploited. The protrusion changes the magnitude anddirection of the fluid flow, enhances the turbulence intensity through flow interaction,and produces severe secondary flow. Heat transfer performance is best at the top ofprotrusion structure, relatively weak in smooth areas, then, the global average heattransfer coefficient has been enhanced.Finally，Experimental study of dimpled tube（dense dimple density） has beenconducted, and the results are in good agreement with the simulated results. Both thenumerical simulation and experimental research show that the protrusion in the dimpledtube can effectively enhance heat transfer but result in a greater resistance, and theresistance increase is more significantly than heat transfer enhancement.