Study On Vortex Dynamics Characteristics And Their Effect On Heat Transfer In A Channel Of Non-Continuous Ring Finned Tube Bundles

Finned tube heat exchangers are widely used in railway locomotive heat exchanger,petrochemical industry,automobile power industry and other industries.The vortex dynamics characteristics in the finned tube bundle channel determine the key functional characteristics of the finned tube heat exchanger:flow and heat transfer characteristics.However,studies on this aspect are less reported at present.In order to provide theoretical basis for further optimization of heat exchanger performance,it is necessary to conduct a detailed study on vortex dynamics characteristics in tube bundle channels.In this paper,independent finned tube and the discontinuous annular finned tube bundle are selected to analyze the vortex dynamics characteristics and the influence on the heat transfer performance.In this paper,appropriate computational region were selected according to the literature and structured grid division was carried out.When the grid quality met the requirement of numerical calculation,the SST k-omega turbulence model was used to evaluate the grid independence.Secondly,the experimental data in the literature are compared to verify the rationality of the algorithm.By changing the fin spacing T_p,the ring fin width H_f to study the vortex dynamics characteristics of the independent annular finned tube and discontinuous annular finned tube channel,including the flow field characteristics behind the finned tube,and the time-averaged resistance coefficient C_dmm and isokinetic characteristics of vortex shedding frequency f and the Strouhal number St along with the Reynolds number Re;The influence of tube spacing ratio L₁/L₂ on the vortex dynamics characteristics of tube bundle channels was added in the study of the vortex dynamics characteristics of tube bundle channels.In this paper,the influence of vortex dynamics characteristics in discontinuous annular fin bundle channels on heat transfer was studied,and the relationship between vortex dynamics characteristics in bundle channels and the averaged Nusselt number Nu_m was obtained.The results show that:when studying the vortex dynamics characteristics of an independent annular finned tube,the average resistance coefficient decreases firstly and then becomes stable with the increasing of Reynolds number.Although the frequency of vortex shedding is affected by the annular fins and different structural parameters,it generally increases linearly with the increase of Reynolds number,and Strouhal number increases with the increase of Reynolds number.In the study of the vortex dynamics characteristics of the channel of discontinuous annular tube bundles,the time average resistance coefficient of the central annular tube in this study is not as large as that of the independent annular tube tubes due to the effects of the structure of tube bundles and annular fins,but the changing trend is similar with the Reynolds number.The frequency of vortex shedding increases linearly with the increasing of Reynolds number and Strouhal number increases firstly and then decreases with the increase of Reynolds number.When studying the heat transfer characteristics of discontinuous annular tube bundle channels,it can be found that Reynolds number and tube spacing ratio have greater contribution to heat transfer of tube bundle channels than fin spacing and the ring wing width.In the study of the non-subsequent influences of vortex dynamics on the heat transfer characteristics of tube bundle channels,it can be found that the heat transfer characteristics of tube bundle channels are related to the velocity of incoming air and the shedding frequency of air in the vortex behind the finned tube,and the shedding frequency of vortex has a great impact on the heat transfer capacity of tube bundle channels.