Experimental Research On The Performance Of Heat Transfer Enhancement Of The Waveform Tube And Development Of The Waveform Flat Tube

The heat transfer performance and resistance characteristic of waveform tube were investigated through experiments with water as the working fluid.Based on the research achievements of waveform tube and flat tube, a new type of tube which is called waveform flat tube is developed. Orthogonal experiment and numerical simulation method are used to study it. And the mechanism of the heat transfer enhancement for the waveform tube and the waveform flat tube was analized.The experiment results show that the total heat transfer coefficient of the waveform flat tube increased by23.8%～58.4%than that of the straight tube. The friction factors of the both tube increase with the increasing Re though the trend of growth of them tended to be flat. The friction coefficient of the waveform flat tube increased from12.3%～38.9%monotonously through calculating by the fitting formula of the friction coefficient. The comprehensive heat transfer performance index JPincrease monotonously with the grow of the Reynolds number and is in the range of1.15～1.65,which means that the heat transfered in waveform tube is of15%～57%larger than that in the straight tube.The waveform flat tube is developedbeased onthe experimental research of waveform tube and the structure and property of the flat tube. The main geometric structure of waveform flat tube is decided by amplitude, chord length, flattening rate and torsional angle. The influence of the four structure parameters to the heat transfer and flow resistance performance of the waveform tube are studied using orthogonal test method and numerical simulation method and the simulation results are surface heat transfer coefficient h and G factorwhich is deduced from the identical pump power consumption formula are used to do the range analysis. The results show that the optimal structure of the waveform flat tube is the amplitude of14mm, chord length of40mm, flattening rate of0.4, torsion angle of60degrees when take the heat transfer coefficient h as the indicators and now the size of the primary and secondary order of the structure is flattening rate of β> amplitude of a> chord length of b>torsional angle of θ. The best structure is the amplitude of5mm, chord length of70mm, flattening rate of0.8, the torsional angle of0degree when take the G factor as the indicators and now the size of the primary and secondary order of them is flattening rate of β>chord length of b> amplitude of a> torsional angle of θ.To study the heat transfer and flow resistance performance of the waveform flat tube, it is compared with smooth straight tube, waveform tube and flat tube respectively in the range of4000≤Re≤e00e. The heat transfer coefficient of the waveform flat tube increased by103~374%than that of the straight tube,56~63%than that of the waveform tube，28~47%than that of the flat tube. The value of overall heat transfer performance of the waveform flat tube is0.89~1.93,1.01~1.06and0.88~1.08compare with straight tube, waveform tube and the flat tube respectively. This shows the waveform flat tube can greatly strengthen heat transfer ability and reduce the power consumption of the pump conveying heat transfer fluid by exchange per unit of heat within a certain range of the Re number.Through simulation and analysis，it shows that heat transfer ability of the waveform and waveform flat tube increased for the secondary flow in the passageway. In addition, the heat transfer ability of the waveform flat tube can still be increased for the characteristic as flat tube which add the scour of the fluid to the boundary layer and velocity gradient near the wall for the increased flow velocity at the same Re number as the straight tube.