Study On Mechanism Of Heat Transfer Enhancement Of Ellipsoidal Vortex Generator

The technology of passive heat transfer enhancement cannot only improve efficiency of heat exchanger, but also reduce the weight and volume of equipments. This method is widely used in various fields because of its no need of extra power and accordance with the requirement of saving energy. The bevel-cut ellipsoidal vortex generator, which is one mode of the passive heat transfer enhancement, is laid on the rectangle channel. The increased ratio relation between heat transfer enhancement and fluid resistance is investigated in order to obtain the best model.Firstly, the rectangle stream channel is set as the foundation model, five kinds of vortex generator with different bevel-cut obliquity are designed to lay in the form of the matrix in the rectangle channel. Then the turbulent model is used in numerical simulation, the variational law of various parameters, such as the velocity, the temperature, the pressure and the vorticity magnitude, is analyzed in details. The various factors of influencing the convective heat transfer coefficient and the pressure loss are discussed. A new estimate criterion is put forward, compared the synthetical effect of the heat transfer enhancement and the fluid resistance decrement between the channel with the vortex generators and the rectangle channel using the new estimate criterion, then the best model is chosed from the competitive results.The optimizational model is chosed to analyze by Large Eddy Simulation, the characteristic of the heat transfer and fluid flow of the channel with the vortex generators is analyzed. The instantaneous characteristic of various parameters, such as the velocity, the temperature, the pressure and the vorticity magnitude, is analyzed to find out the temperature stripe structure that is similar with the velocity stripe in the temperature field. The interaction between the parameters in the temperature field and the parameters in the velocity field is analyzed, and the influence that heat transfer enhancement mechanism of vortex generator to the fluid resistance is induced. The researchful result is the basis of the further study on the passive controls of vortex generator on the velocity filed and the temperature field.