Numerical Study On Convection Heat Transfer And Flow Resistance Characteristics Of Twisted Inner Fin Tube Heat Exchanger

With the deepening of the energy crisis,the requirements for the development of clean energy and the improvement of energy utilization efficiency have become higher and higher.Therefore,it has become a trend to strengthen the research on heat exchange technology.The heat exchanger strengthening is generally divided into two directions,one is to study new types of heat exchangers,and the other is to use various strengthening measures to enhance the heat exchange efficiency of heat exchange tubes.Spiral twisted tube is one of the efficient heat exchange tubes.The special structure of the spirally twisted tube can make the fluid flow longitudinally and generate a secondary swirl flow to achieve enhanced heat transfer in the tube.Moreover,the spiral twisted tube heat exchanger is a heat exchanger for the purpose of improving the tube-side heat transfer coefficient and reducing the shell-side pressure drop.In this paper,spiral twisted tubes and discontinuous inclined fins are combined to form a twisted internal finned tube model.Fluent and other software are used to numerically simulate the heat transfer tube model.Factors such as different pitches,different long and short axes,and different numbers of fin rows are used to calculate heat transfer.The effects of tube heat transfer and flow resistance characteristics are further analyzed.The heat transfer and flow resistance characteristics of twisted internal fin tube heat exchangers are further analyzed.the result shows:(1)The smaller the pitch of the twisted inner fin tube,the larger the Nussel number,the larger the resistance coefficient,the larger the number of comprehensive heat transfer factors,and the better the heat transfer effect.(2)Under the same Reynolds number,as the ratio of the long axis to the short axis increases,that is,the flatter the heat exchanger tube,the Nussel number is also increased,and the Nussel number is increased by about 18% at the maximum.The corresponding resistance coefficient increases,and the maximum resistance coefficient increases by about 28%.The enhanced heat transfer factor is gradually increased,but the change is relatively small.(3)With the increase of fin height,the Nussel numbers increased by 2.9%,3.9%,5.4%,and 7.6%,respectively.The fin height increased the most by 2mm.Under the same Reynolds number,the inner fins were distorted.The resistance coefficient of the tube increases with the increase of the fin height;the fin height is between 0 and 2mm,and the enhanced heat transfer factors are increased by up to 2.8%,3.0%,4.7%,and 5.9%,respectively.(4)With the increase of the number of discontinuous inclined fins,the Nussel number gradually increases,the resistance coefficient gradually increases,and the enhanced heat transfer factor of finbed tubes is increased by 9% compared with unfinbed twisted tubes.The finned heat exchange tube has the best heat exchange effect.(5)With the increase of Prandtl number,the Nussel number gradually increases,the resistance coefficient is almost unchanged,and the enhanced heat transfer factor also gradually increases.The heat transfer effect with a high Reynolds number is better.(6)For twisted internal finned tube heat exchangers,the smaller the pitch,the greater the number of fin rows,the larger the corresponding Nussel number,the greater the enhanced heat transfer factor,and the better the heat transfer effect;Tube heat exchangers are better than twisted tube heat exchangers without fins.Finally,through the research results,it is found that the heat transfer effect of twisted internal finned tubes is better than that of twisted tubes,which has played a theoretical guiding role in the study of enhanced heat transfer and has research significance.