| Energy-saving and emission reduction has become an important link of the economic and national development in China, even all the countries in the world, and the practical and efficient heat transfer enhancement technology is an important means of energy-efficient, which is widely used in the industrial fields, such as petroleum, chemical industry, energy, metallurgy etc, also has a wide range of applications in the fields of aerospace, electronics cooling and the safety use of nuclear energy. Therefore, the development of new types of heat transfer enhancement technology and highly efficient heat exchanger can bring huge economic and social benefits.In this paper, a three dimensional numerical simulation were carried out to study the flow and heat transfer characteristic outside the elliptical finned elliptical tube. The influences of fin parameters and inlet flow velocity on heat transfer coefficient and flowed friction were researched. Comparing with the circular finned circular tube which has the same structure parameters (equivalent diameter, thickness of fin and the surface area), for the same condition, there are nearly less difference in the heat transfer coefficients between elliptical tube and circular, but the flowed friction of elliptical tube reduced obviously. By using the theory of field synergy, it was found that the local heat transfer on the fin located on the windward side is better than that on the leeward side. Increasing the fin area on the windward side and reducing that on the leeward side properly, the heat transfer could be enhanced, and at the same time, the flowed friction could be reduced.From the shortcomings of the traditional manner heat transfer enhancement, according to the theory of heat transfer enhancement in the core flow area put forward by Prof. Liu Wei, an experiment by adding different twists in the core flow area was done to validate the theory, and provides a theoretical basis for the new type of enhanced future heat transfer technology. By compare the analysis of convective heat transfer enhancement theory of limited space inside tubes with bulk space, we propose the heat transfer enhancement manner by adding insert in the core flow area that can improve the overall performance of heat exchangers by achieving a high convective heat transfer coefficient and reducing the drag force, thus strengthening the integrated heat exchanger tubes to enhance performance. With water as the working fluid, the heat transfer performance of enhanced tubes which are added different twisted tape with the width of each in the core flow area are investigated experimentally. The results using the plain tube serve as a basis for comparison of the cases with twisted tape.From the analysis of the experimental results, we can see that to ensure the same twist ratio Y of the three twisted tapes used in the experiment, three twisted tapes with different width ( d 1 = 6mm, d 2 = 10mm,d 3 = 14mm) of the heat transfer performance with the twisting of the reduced width gradually reduced, and twisting with the more narrow the faster the heat transfer performance at the same time, also reduce the flow resistance. Comprehensive performance evaluation from the value of coefficient of PEC can be seen, twisted tape 2 is better than twisted tape 1 and 3, and numerical simulation results shows that when the width of the twisted tapes is about half time of the diameter of the smooth tube, the performance is the best. This proved that the theory of the core flow area heat transfer enhancement is absolutely correct.Verified by experiments, we can based on the theory of the core flow area heat transfer enhancement, combined with numerical simulation and experimental means, not only can explain the existing heat transfer performance of heat exchanger performance, and can guide the way the original heat transfer enhancement optimization, but also to develop new technology of heat transfer enhancement, design new heat transfer exchanger, have broad application prospects.
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