Research On Heat Transfer Enhancement By Fluid-induced Vibration Of The Surface Evaporation-type Air Cooler

The surface evaporation- type air cooler was a high-effect and energy-saving cooling equipment which inosculated water and air cooling, heat and the mass transfer and were of advantages of both, this heat exchanger had more advantages than others which was the new direction of the development of air-cooling technology. The heat-transfer performance of the equipment was enhanced with heat-transfer enhancement technology by fluid-induced vibration. As a heat transfer, the heat-pipe vibration of the traditional structure could not be used, only to be prevented. The topic proposed that heat-exchanger straight pipes were changed to the structure like the two-dimensional snakelike pipes, the two types of pipe were studied in this paper.Firstly, mechanism of flow-induced vibration was introduced, the traditional heat-transfer straight pipe was analyzed on nonlinear vibration. The results showed the traditional method of elimination vibration was increasing rigidity (k_e), which could not solve the difficult question effectively, Therefore this topic used the structure of lower rigidity and lower natural frequency, that was the two-dimensional snakelike pipe of heat transfer.The ways and means of heat transfer enhancement were introduced and the mechanism of enhancement by vibration. The ways of heat transfer enhancement had many kinds, enhancement by vibration was one of them. The heat transfer enhancement by fluid-induced vibration belonged to the technology of active heat transfer enhancement, the application of this technology is at the initial stage regardless of at home or abroad; The heat-transfer process of the surface evaporation-type air cooler, the computation content and the fundamental formula were analyzed by the theory of heat transfer.The vibration state of the two-dimensional snakelike pipe and the straight pipe were simulated by ANSYS software, and reached the fist ten model of vibration , the natural frequencies range of model I were between 23.347 and 958.55 Hz, the range is smaller; the frequencies range of model II were from 287.67 to 11225Hz, the frequencies value were higher, and the scope was larger. Therefore under the same initial conditions, the two-dimensional snakelike pipe had lower natural frequency, smaller amplitude and smaller accepted force. It showed that it was apt to vibrate gently, and to benefit to improve performance of heat transfer.Finally, a model of surface evaporative air cooler was designed, the heat transfer performance of the snakelike pipe was studied on physics experiments, the results of experiments was analyzed, the heat transfer coefficient was calculated; At the same time, the heat transfer coefficient of the surface evaporation-type air cooler in the working area of blast furnace in Anshan Iron & Steel Complex was calculated, and the result of comparison showed that the heat transfer coefficient of the experimental model was higher than that of the equipment Anshan Iron & Steel Complex.