| Enhanced heat transfer has important research significance and application prospects in industrial production.Electrohydrodynamics(EHD)enhanced heat transfer technology,as a very promising active enhanced heat transfer technology,has gained a lot of attention from scholars at home and abroad in recent years.The principle is that the ionic wind formed by the ionization of air under high voltage disrupts the thermal boundary layer and enhances convective heat transfer.Since this flow is generated by electrostatic force,EHD enhanced heat transfer technology has many advantages such as miniaturization of equipment,low power consumption,rapid response,and no noise.This enhanced technology is widely used in many fields such as food drying,microelectronic cooling,and the aerospace industry.In recent years,many scholars have worked to explore the design of EHD-enhanced heat transfer devices with higher performance.In this paper,we review these studies and find that these strengthening ideas are usually limited to specific parameters and lack universal design guidelines based on dimensionless numbers.Based on this,this paper dimensionlessizes the main parameters affecting the performance of EHD devices,conducts an in-depth study of the effects of these parameters,and proposes design guidelines for improving the heat transfer efficiency of channels based on dimensionless parameters.In this paper,numerical simulations of rectangular channels with single-electrode configuration and multi-electrode configuration are carried out by varying the dimensionless parameter secondary flow intensity NEHD using finite element method.The flow heat transfer characteristics under single-electrode configuration and multielectrode configuration are investigated,and four main flow patterns and their influencing factors are analyzed,including the secondary flow intensity NEHD,dimensionless channel height H*,and dimensionless electrode spacing l*.The results show that both too strong and too weak secondary flow intensities lead to a decrease in the average Nussle number of the channel.Too low a distance between electrodes causes adjacent vortices to form a hysteresis region,which leads to a significant decrease in the average Nusser number.Three flow types,barrier effect,blocking effect and interference effect,will lead to at least 8%,5%and 13%reduction in the average Nussle number,respectively.The barrier effect is only affected by the secondary flow strength NEHD.The blocking effect is affected by the secondary flow strength NEHD and the channel height H*,but as the channel height increases the blocking effect requires a lower secondary flow strength to occur.The interference effect is influenced by the electrode spacing l*and the channel height H*.Based on the above research results,this paper proposes a channel maximum heat transfer efficiency secondary flow intensity for both single-electrode configuration and multi-electrode configuration:NEHD=2.0.When the EHD in the channel is a multielectrode configuration,the spacing 1 of adjacent electrodes should ensure l>0.014 m.In order to quantitatively predict and eliminate the three effects,the flow pattern spectrum of rectangular channel with two electrodes is plotted in this paper to guide the corresponding EHD device design. |
