Research On Flow And Heat Transfer Characteristics Of Combined Fin With Corrugation And Vortex Generator

Perforated fins,louvered fins,wavy fins and fins with vortex generators are highly efficient passive heat transfer enhancement fins which have the characteristics of good heat transfer enhancement and low pressure loss and are widely used in the field of heat transfer enhancement of heat exchanger.With the increasing requirements of heat transfer performance and compactness of the heat exchangers,the existing single heat transfer enhancement technology is difficult to meet the requirements.In order to pursue a heat transfer surface with higher performance,the combined heat transfer enhancement technology is expected to become the main method and research hotspot for improving the heat transfer performance of the heat exchanger.At present,there are few studies on the combined heat transfer enhancement technology.Some research on the combined heat transfer enhancement technology of wavy fin and vortex generator are mostly concentrated in the fin-and-tube heat exchangers,but the research on the corrugated plate heat exchangers with vortex generators has not been reported.In this paper,the heat transfer enhancement technology of the combination of wavy fin and vortex generators in the channel of the plate heat exchanger is numerically studied in the range of laminar and turbulent flows.The development of longitudinal vortices,the effects of the attack angle and position of the vortex generators on the heat transfer and flow characteristics of the fin are analyzed.The results show that the heat transfer performance can be greatly improved by the combination of wavy fin and vortex generators.The main conclusions are as follows:In the channel of the combination of the wavy fin and vortex generators,the longitudinal vortices are strengthened when the fluid flows over the crests of the bottom fin(the troughs of the top fin),and the longitudinal vortices are weakened when the fluid flows over the troughs of the bottom fin(the crests of the top fin).The number of longitudinal vortices gradually increases with the fluid flows downstream.Besides,the longitudinal vortices obviously promote the mixing between the cold and hot fluids in the channel and enhance the heat transfer performance of the wavy fins.The average Nu and comprehensive performance evaluation factor JF of the combination of wavy fin and vortex generators are the largest at the attack angle of 60°.Compared with the wavy fin without vortex generators,the average Nu of the combination of wavy fin and vortex generators increases by 31.5%,while the friction factor f increases by only 23.4%,and the comprehensive performance evaluation factor JF can be up to 1.23.Correlations for average Nu and friction factor f as functions of Re and attack angle are obtained in laminar and turbulent regimes,respectively.The differences in Nu and f between the correlations and the numerical results are within ± 5.2%and ± 6.3% under laminar flow,and within ± 3.8% and ± 7.7% under turbulent flow,respectively.The installation position of the vortex generator also has a significantly effect on the flow and heat transfer characteristics of the combination of the wavy fin and vortex generators.The position of the vortex generator has a great influence on Nu while has little influence on f.The performance of the vortex generators on the suction side of the wavy fin is better than that on the pressure side.Comparing with the common wavy fin without vortex generators,Nu and f with the vortex generator installed at the optimal position of the suction side increase by 44.3% and 29% and the maximum JF is 1.33,while Nu and f increase by 34.2% and25.9%,and the maximum JF is 1.25 when the vortex generators are installed at the optimal position of the pressure side.