| Heat exchangers are widely used in petrochemical industry,electric power metallurgy,aerospace,cryogenic refrigeration and other fields.It is of great sig nificance to research and develop effective heat transfer enhancement technolog y to reduce equipment investment and improve energy efficiency.Interpolating spoiler elements in heat exchanger tubes is one of the effective ways to enhan ce convective heat transfer in tubes.Scholars at home and abroad have carried out a series of studies on them,but spin spoiler is still a problem.Componen t research needs to be further improved.Firstly,a new type of fixed branch spoiler was developed,and the flow a nd heat transfer characteristics of branch spoiler heat exchanger tubes with diff erent structural parameters were simulated under laminar flow conditions(Re=300~1800).The Nusselt number,friction coefficient and comprehensive heat tran sfer evaluation factor with Re number are studied by changing the pitch P,bra nch number n and inclination angle ? of the branch spoiler.The results show t hat Nusselt number,friction coefficient and comprehensive evaluation factor inc rease with pitch decreasing,and the heat exchanger with small pitch has the hi ghest Nusselt number,friction coefficient and comprehensive evaluation factor.The larger the number of branches,the greater the friction coefficient of the in sert in the heat exchanger tube,the higher the_value of the heat exchanger tub e when the number of branches is n=3,and the highest comprehensive heat tra nsfer performance of the heat exchanger tube when the inclination angle is ?=45°.Secondly,in order to simulate the passive rotation process of the rotating spoiler in the heat exchanger tube under specific working conditions,UDF pro gram was compiled and the flow and heat transfer characteristics under turbule nt flow conditions(Re=5000~30000)were simulated by using 6DOF dynamic g rid model.The variation law of the rotational speed of different pitches with R e number was obtained,and the pressure characteristics of the heat exchanger t ube with different pitches were analyzed.The influence of velocity and temper ature characteristics.By comparing and analyzing the effects of different pitch ties on Nusselt numbe,friction coefficient and comprehensive evaluation factor,it is found that the Nusselt number of heat exchanger tubes with different pit ch ties is basically the same.Compared with the large pitch ones,the small pi tch ones have larger friction coefficient,so the large pitch ones have higher co mprehensive heat transfer performance.Finally,hollow spiral ties and straight-curved hollow spiral ties are developed on the basis of ordinary spiral ties.Through numerical simulation of flow and heat transfer characteristics of three kinds of spiral ties heat exchanger tub es,the results show that the rotational speed of straight-curved spiral ties is si gnificantly lower than that of ordinary spiral ties and hollow spiral ties,and th ere is a distinct secondary rotational flow in the heat exchanger tubes.Nusselt numbe of straight-curved hollow spiral ties is the highest,Nusselt numbe of ho llow and ordinary bonds is relatively low,but friction coefficient of straight-cur ved hollow spiral ties is the largest,resulting in the lowest comprehensive heat transfer performance. |
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