Numerical Research On Heat Transfer And Flow Resistance Performance Of Twisted Tube Heat Exchanger

Twisted tube heat exchanger was a high efficient self-supporting heat exchanger. Using high efficiency twisted tubes instead of conventional circle tubes can reduce the equipment cost and energy consumption, and can significantly improve the heat transfer efficiency.A reseach of numerical method was done for twisted tube heat exchanger and the limitations of different near wall treatment were discussed. The comparison of accuracies between five two equation turbulence models in circle tube and twisted elliptic tube calculations showed that SST k-co turbulence model was better. With the difficulty of mesh size control, Scalable wall function was a reasonable choice on the tube side calculation.A numerical research on heat transfer and flow resistance performance of twisted elliptic tube and twisted trifoliate tube was carried out considering the influence of cross-section, lead, Pr and Re.With the decrease of B/A, D1(inscribed circle diameter), dt (transitional arc diameter) and S, Nusselt number and resistance coefficient of twisted elliptic tube and twisted trifoliate tube increased, and comprehensive property was improved. So the comprehensive properties of28×9.6,S=150twisted elliptic tube and10×5, S=100twisted trifoliate tube were best in the objects of studied. With the increase of Prandtl number, Nusselt number of twisted elliptic tube and twisted trifoliate tube increased, however the resistance coefficient was no apparent change. Comprehensive property of twisted tube increased quickly when the Prandtl number was less than100, and then it changes slightly. With the increase of Reynolds number, Nusselt number increased, while resistance coefficient decreased. The comprehensive property increased first and then decreased with the Reynolds number increasing. The optimal comprehensive property was in Re range1000-2000.The dimensionless correlations for Nu and f in tube side are obtained using the method of multiple linear regressions. They are based on the104groups of data from twisted elliptic tube and88groups of data from twisted trifoliate tube when Re=2000-20000. Dimensionless correlations of twisted elliptic tube: Dimensionless correlations of twisted trifoliate tube:The numerical research of shell side of twisted tube heat exchanger showed that design of reasonable structure for clearance between pipe bundle and shell can improve heat transfer performance. Congsidering the performance of tube side and shell side, twisted trifoliate tube heat exchanger was smaller in size when the performance of twisted elliptic tube heat exchanger and twisted trifoliate tube heat exchanger was similar.