| Energy saving has become more urgent and important, Development of society need to consume more energy and energy storage capacity is limited, and this needs to be done in the process of efficient use of energy in order to try to delay the use of energy shortage. High efficiency heat exchanger can achieve maximum economic benefits under the condition of material consumption. Efficient use of energy is achieved through heat transfer enhancement, Enhanced heat transfer technology has been widely exist in petroleum, chemical, energy, metallurgy, materials, aerospace, electronics cooling, the use of nuclear energy and other fields.However, traditional plain tube used in many heat exchangers has the shortage of low heat transfer. It is difficult to meet the requirements of all aspects of heat transfer process. the techniques of heat transfer enhancement is an important means of advocating high efficiency and energy saving. The techniques for heat transfer enhancement can be divided into two categories. One is the active strengthening technique and the other is the passive one. Tube inserts are practical and popular, especially in the working medium with high viscosity fluid in heat transfer. Tube inserts can disturb and improve heat transfer by mixing fluid between the near wall zone and mainstream zone, and distribution of velocity field and temperature field inside to improve the synergy between them, so as to acquire low resistance and high efficient heat transfer performance.Firstly, this paper expounds tube inserts strengthen heat transfer mechanism and advantage, tube inserts research status at home and abroad are introduced. At the same time, field synergy theory and CFD numerical simulation of heat transfer enhancement in application are summarized. A brief introduction to the heat transfer enhancement and the evaluation method is presented.A tube in which inserted with fan-shaped conical strip and water as working fluid is investigated by Fluent. The flow and heat transfer characteristics of the tube in which inserted with fan-shaped conical strip relates to the field angle, dip angle a, Spacing s, Leaf number n and so on. In the process of numerical simulation, selected different structural parameters, and simulated different structural parameters under five kinds of Reynolds number; and discussed the influence of different structural parameters to Nusselt number, flow friction coefficient, comprehensive properties; analyzed of strengthening the overall collaborative by use of the theory of field synergy, and get the size of the average synergy Angle.The results show that inserted fan-shaped conical strip can significantly strengthen the heat transfer. When the Re is in the scope of 12000~36000, the PEC value can be1.26~2.07.With the same field angle, the PEC value decreases with the dip angle a. When the tube is fixed with four fan-shaped conical strip, the heat exchanger comprehensive performance is the best for the angle of 30, followed by45 ˊs, the minimum is 60 ˊs. and when the leaf number is 2,PEC value reach the maximum. After orthogonal analysis, the order of the primary and secondary factors and optimal structural parameters of the tube that a=20o、40o、n=2、s=72mm is gotten. |
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