Experimental Investigation Of Heat Transfer Characteristics Of High Prantdl's Number In Three-dimensional Internally Finned Tubes

Single-phase forced convective heat transfer inside tube is an important research realm in the technology of heat transfer enhancement. It plays an important part in saving energy and decreasing the volume and weight of heat exchanger. In this paper, three-dimensional internally finned tube (3-D IFT) can be used to enhance single-phase forced convective heat transfer inside tube.In this paper, the working fluid is original lubricating oil. Experimental study of the heat transfer and flow friction characteristics of high Prandtl's number fluid in eight 3-D IFT with spiral arrangement fins and four 3-D IFT with in-line arrangement fins. The experimental plan applies Orthogonal Experiment Method in the Reynolds number range from 40 to 800 and Prandtl's number range from 300 to 2500. The former experimental focuses of research are 3-D IFT with staggered arrangement fins and 3-D IFT with mixing arrangement fins (staggered arrangement fins, spiral arrangement fins and in-line arrangement fins). This paper firstly research 3-D IFT with spiral arrangement fins. This research focuses on it.The experimental result shows that the flow states in 3-D IFT have three regions: laminar, transitional and turbulent. At the same time, we regress experimental data and get the fitting criterion equation for critical Reynolds number judge of the flow states. By the experiment, we came to the conclusion that the 3-D IFT's transitive Reynolds number of flow states is decrease more rapidly than smooth tube's. The relative fin height, relative fin width, relative fin-axial-pitch and relative fin-circular-pitch have an effect on the transitive Reynolds number.Analyses and reduces the experimental data by the least square method and regress the experimental data to get the Nusselt and Fanning friction fitting criterion equations. Analyses the effect of the geometry dimension of 3-D IFT for the characteristics of heat transfer and flow friction. Through the analysis of the thermodynamic performance coefficient and heat augmentation ratio, we can determine that the best structure parameter of 3-D IFT with spiral arrangement fins and in-line arrangement fins.In this paper, we compare thermodynamic performance coefficient among spiral arrangement fins, in-line arrangement fins and staggered arrangement fins. The comparative condition is that working fluid is original lubricating oil, the Reynolds number and Prandtl's number are the same. The result is that when the working fluid ishigh Prandtl's number fluid, the 3-D IFT with spiral arrangement fins have the highest thermodynamic performance coefficient in transitive and turbulent zone, the 3-D IFT with in-line arrangement fins have highest thermodynamic performance coefficient in laminar zone.The fitting criterion equations and other results that are obtained by the experimental data can be used in the design field of heat exchanger. The research supplies some theory bases for engineer use.