Study On The Application Of Vortex-induced Vibration Of Flexible Plate For Enhancement Heat Transfer In Spiral Plate Heat Exchanger

Compared with other heat exchangers,spiral plate heat exchanger has the advantages of compact structure,good heat transfer performance,low heat loss,and is widely used in various fields of industrial production.In order to further improve the heat transfer performance,the combination of advanced enhanced heat transfer technology and spiral plate heat exchanger is particularly important for the heat transfer performance improvement and design of a new type of spiral plate heat exchanger.Vortex-induced vibration technology combines the advantages of passive technology and active technology,which can not only enhance the heat transfer efficiently,but also does not need additional energy input and complex devices.Vortex-induced vibration technology uses vortex to induce vibration,and throws the vortex to the wall during the vibration process to break the thermal boundary layer and enhance the heat transfer performance of the heat exchanger.This thesis investigated the effect of vortex-induced vibration heat transfer enhancement technology on the characteristics of fluid flow and heat transfer of a spiral plate heat exchanger under turbulent flow condition.The effects of different lengths of flexible plate and numbers of flexible plates on the characteristics of fluid flow and heat transfer performances were also investigated.The main findings are as follows:The heat transfer performance of the spiral plate heat exchanger is significantly improved by vortex-induced vibration because the Karman vortex can play a role in breaking the thermal boundary layer and enhancing the heat transfer performance of the heat exchanger.When the length of flexible plate is 4.5mm,the value of Nu can generally improve by more than 34% under different operating conditions.At an inlet velocity of 6.5 m/s,the maximum enhancement of Nu is 49.66%.Since the driving force of the vibration of the flexible plate is provided by the Karman vortex street generated by the fluid during the flow,this results in a general increase of the pressure drop in the channel by more than two times.The length of the flexible plate have a large effects on the heat transfer performance of the heat exchanger.According to the research of three flexible plates with different lengths.When the length of the flexible plate is 6mm,its Nu is the largest,the general improvement is above 69%.,and a maximum increase of 75.02% at an inlet velocity of 6.5 m/s.When the length of the flexible plate is 6mm,JF is generally greater than 1,and the maximum value is1.108 when the inlet speed is 6.5 m/s.The number of the flexible plates also has great influence on the heat transfer performance of heat exchangers.When the plate length is 4.5mm,the influence of different number of flexible plates on heat transfer performance is studied.It is found that adding three sets of flexible plates can effectively improve JF and Nu of spiral plate heat exchanger.Under different inlet speeds,Nu is generally improved by more than 44% compared that of the smooth channel,and JF is generally greater than 1.When the inlet velocity is 6.5 m/s,,the improvements of JF and Nu are the most.Nu increases by 65.4% and JF is up to 1.13.The heat transfer and the overall heat transfer performance are substantially improved.