Study On Heat Transfer Tube Characteristics Of Heat Exchanger With Inner Noncontinuous Torsional Belt And Spouting Spiral

Heat exchanger is a kind of common heat exchange equipment in industry,which is commonly used in petroleum,chemical,steel,metallurgy,refrigeration,pharmaceutical and other industries.Among them,shell and tube heat exchanger is the most common,but due to the insufficient flow of fluid in the tube and the easy scaling of the inner wall,its heat exchange efficiency is not high,which affects the industrial production efficiency.According to this,many scholars have studied the enhanced heat transfer in the heat exchange tube.In this paper,based on the relevant research,a new method of enhanced heat transfer in the tube is studied,and its heat transfer and resistance characteristics are studied by numerical simulation method,combined with the comprehensive evaluation factor,its comprehensive performance is analyzed.The main contents and achievements are as follows:1)According to the structure and working condition of a vertical heater in use,a new method of heat transfer enhancement under the combined action of injection screw and discontinuous twisted strip in the heat exchange tube is studied;2)The mechanism of enhanced heat transfer is studied from three aspects: enhanced coefficient of enhanced heat transfer,enhanced coefficient of resistance and comprehensive evaluation factor.The results show that the heat transfer boundary layer can be directly destroyed by the injection produced by the injection spiral tube,so as to reduce the thermal resistance.The spiral tube placed on the inner wall of the heat exchange tube near the wall can disturb the fluid close to the wall,which makes the fluid flowing along the straight line of the inner wall of the tube produce vortex,and the fluid produces velocity in the radial direction,which is consistent with the direction of heat transfer,and can strengthen the heat transfer of the fluid in the radial section of the tube,so as to promote the heat transfer.The discontinuous twisted strip inside the tube can rotate the fluid flowing along the axial direction,generate radial velocity,promote the mixing of the central fluid and the fluid near the wall,enhance the heat exchange between the fluid particles,and promote the heat exchange.At the same time,the twisted strip adopts the discontinuous structure design,which can reduce the flow resistance as much as possible;3)Seven factors that have great influence on heat transfer enhancement are studied by single factor experiment method: injection speed V,pitch P of injection screw pipe,layout density P/n of injection hole(number of injection holes arranged in a pitch P of injection screw pipe is n),width D of discontinuous twisted band,torsion Y of discontinuous twisted band,length nH of discontinuous twisted band(H is twisted band pitch,H = DY,length of single twisted band n pitches)and spacing S of discontinuous twisted strip;4)The orthogonal experiment was designed to optimize the above seven factors as a whole,to find the primary and secondary order of the influence of each factor on the results,and to meet the optimal parameter combination of this experiment.The results show that the injection velocity V has the greatest influence on the comprehensive evaluation factors,followed by the injection hole layout density P/n,the length of single segment of the discontinuous twisted band nH,the spacing S,the width D,the pitch P and the twist rate Y of the discontinuous twisted band.That is to say,the primary and secondary order of the influence of each factor on the experimental results is V > P/n > nH > S > D > P > Y.When the comprehensive performance of heat exchange tube is the best,the combination of factors is as follows: V = 1.4m/s,P = 130 mm,P/n = P/5,D = 25 mm,Y = 3,nH = 3h,S = 80 mm.