Effect Of Pulsating Flow And Wall Vibration On Heat Transfer In Transverse Tube

This work was partly supported by National Natural Science Founding(No.50976080).Nowadays, energy issue becomes a major issue which limits human development, such as energy shortage, the highlights of the safe use of nuclear energy; more and more scholars are concerned about energy-efficient technology research and development. As two common kinds of heat transfer forms of unsteady flow, pulsating flow and wall vibrations both have good heat transfer enhancement effect. In this paper, the influence of pulsating flow on heat transfer flow characteristics inside and outside of transverse tube was studied, and also, the heat transfer characteristics under the action of pulsating flow and wall vibration, the main research achievements are as follows.The numerical model of pulsating flow through into transverse tube was established, and the FLUENT was adopted to simulate heat transfer and flow characteristics of the transverse tube when the low-velocity flow passed by. Numerical simulation results showed that: under the pulsating flow, there were vortexes generated and divorced continuously near the wall which enhanced energy and mass transfer in the diameter direction of the inner tube (the direction of the temperature gradient); pulsating flow caused the wall shear force changed periodically.The calculation mode of pulsating flow around the stationary tube was simplified, and then the surface heat transfer coefficient and the instantaneous lift, drag curve were analyzed. The results showed that: pulsating flow enhanced the tube surface heat transfer coefficient; by Fourier transformation, the frequency of vortex was close to that of pulsating flow , and the tube vibration problems caused by pulsating flow were discussed. The flow and heat transfer characteristics of vibration tube were studied when the pulsating flow passed by with dynamic mesh technology. The results showed that: pulsating flow and vibration tube enhanced heat transfer effect; the surface heat transfer coefficient of vibration tube increased with the increase of amplitude and frequency of pulsating flow and the tube vibration amplitude , but tube vibration frequency had little influence of surface heat transfer coefficient; the heat transfer enhancement obtained mainly due to the secondary flow generated by pulsating flow and vibration tube that enhance the compound of hot and cold fluids, which enhanced the quality, energy transportation.The steady temperature water bath experimental system was constructed,then the heat transfer characteristics of pulsating flow in transverse tube and light tube were tested. Through the experiments, that the pulsating flow in ordinary tubes did not have the effect of enhanced heat transfer was verified; when the amplitude of pulsating flow tended to be larger or reciprocating flow, it has a certain effect on enhanced heat transfer, which verified the correctness of numerical simulation and conclusions further.