Thermodynamic Performance Study Of Air In Three-Dimensional Internally Finned Tubes With Different Arrangement Fins

Single-phase forced convective heat transfer inside tube is an important research realm in the technology of heat transfer augmention. It plays an important part in saving energy and decreasing the volume and weight of heat exchanger. In our studies, three-dimensional internally finned tube(3-D IFT) is a type of new heat transfer enhanced tubes which can be used to enhance single-phase forced convective heat transfer inside tube. Compared the 3-D IFT with smooth tube, the result shows that it has perfect heat transfer enhancement effect and good thermodynamic performance. But because of irregularity of its fin, analysis and research of its enhanced heat transfer mechanism are not enough completed at present. The effects of various structure parameters and fins arrangement of the three dimensional extended surface on heat transfer performance in the 3-D IFT have not been studied systematically.3-D IFT have three fin arrangements: staggered arrangement fins, in-line arrangement fins and spiral arrangement fins. The former only cursorily studied staggered arrangement fins systematically and obtained the heat transfer criterion of 3-D IFT, while the paper mainly studies 3-D IFT of in-line arrangement fins and spiral arrangement fins systematically. Through the conventional analysis of Othorgonal Testing Method results, we can determine that the best structure parameters of 3-D IFT with in-line arrangement fins and spiral arrangement fins. At the same time, I also compare synthetically of fins' size, spiral progression and fin arrangement of 3-D IFT of three fin arrangements.In this paper, the working fluid is air. Experimental study of four different structure parameters of 3-D IFT of in-line arrangement fins and eight different structure parameters of 3-D IFT of spiral arrangement fins in the Reynolds number range from 300 to 35000 is performed to investigate the thermodynamic performance. I analyses and regresses the experimental datas by the least square method to obtain the Nusselt number and Fanning friction fitting criterion equations. The experimental results of air heat transfer show that relative fin wide, relative fin circumference pitch, relative fin height and relative fin pitch of 3-D IFT with in-line arrangement fins and spiral arrangement fins all have effect on heat transfer and flow friction. Besides, I list, compare and analyse these equations of 3-D IFT of three different fin arrangements inorder to provide important foudation of choice in practice.In addition, I first find that there is increasing unsteadily zone of thermodynamic performance in transitional flow when air flows 3-D IFT. In this zone, heat transfer augmention ratio and resistance increment ratio of 3-D IFT will decrease acutely, but thermodynamic performance coefficient in this zone increases more slowlier than in the laminar flow. The important purpose of detecting this zone is to provide some theories of choosing 3-D IFT flowing state in engineering practice.The fitting criterion equations and important results which are obtained by the experimental datas can be used in the design field of heat exchanger that can choose arrangement modes, various structure parameters, computing heat transfer coefficient and resistance. The research provides some bases for practice.