Study On Flow Boiling Heat Transfer And Pressure Drop Characteristics Of In Mini-channels With Aitifical Cavity Surface Under Electric Field

With the development of science and technology,the traditional mini-channel is more and more unable to meet the heat dissipation requirements of highly integrated device system.In this paper,the mini-channels with artificial cavity surface is made by laser drilling technology.The flow boiling heat transfer and pressure drop characteristics of R141 b in the mini-channels with artificial cavity surface under the action of electric field are studied,which provides a reference for integrated heat dissipation in new fields such as electronic chips.The main research contents are as follows:(1)Using different artificial cavities layout schemes at the bottom of the mini-channels,the flow boiling heat transfer test of R141 b in the mini-channels with artificial cavities on the surface under the action of the electric field was carried out on a test platform to which an external DC electric field could be applied.The results show that: The electric field has a significant strengthening effect on the flow boiling heat transfer in the mini-channel with artificial cavities on the surface,and its electric field strengthening factor EEF between 1.03 and 1.99;the mini-channels with artificial cavities on the surface have a higher electric field enhancement factor at low heat flux density than ordinary smooth mini-channels under the same conditions,but the opposite is true at high heat flux density.The strengthening effect of the electric field on the flow boiling heat transfer increases with the increase of the inlet supercooling and the mass flow rate,and decreases with the increase of the heat flux density.The outlet thermal equilibrium dryness will reduce the strengthening effect of the electric field,which will lead to the average saturated boiling heat transfer coefficient drops.In addition,the artificial cavity structure parameters have a certain effect on the electric field strengthening effect.In addition,the artificial cavity structure parameters also have a certain effect on the enhanced flow boiling heat transfer of the electric field.(2)The visual research was carried out by a high-speed camera,and the numerical simulation was carried out using COMSOL software to study the mechanism of electric field heat transfer enhancement of the flow boiling in the mini-channels on the surface of the artificial cavities.At the same voltage,the number of bubbles in the mini-channels with artificial cavities on the surface is higher than that in the case of no electric field,which is higher than that of ordinary smooth surface mini-channels.The surface of the microchannel has artificial bubbles with a smaller confined bubble equivalent diameter,and the artificial cavities extend the effective heat flux density range of electric field strengthening,which makes the electric field has a better strengthening effect on the heat transfer of the mini-channels with artificial cavities on the surface.(3)The boiling pressure drop characteristics of R141 b flow in mini-channel with artificial cavities surface under the action of electric field were studied.Under the experimental conditions,the total pressure drop,two-phase flow pressure drop and two-phase friction pressure drop ratio per unit length of the flow boiling in the mini-channel with artificial cavities surface under the action of electric field increase by 19.5%,38.4% and 19.1%,respectively.By studying the time-domain characteristics of the pressure drop,it is found that the electric field increases the pressure drop instability in the mini-channel with artificial cavities surface,but compared with the mini-channel with normal smooth surface,the standard deviation of the pressure drop in the mini-channel with artificial cavities surface decreases,whether or not an electric field is applied.