Experimental Study On Heat Transfer Characteristics Of Horizontal Flow-Jet Impingement Coupled Boiling

As the integration level of microelectronic components continues to increase,the heat flux per unit area sharply increases.High temperatures causing device damage or performance degradation have become one of the main reasons limiting the development of microelectronic chips.Traditional air-cooling and single-phase liquid-cooling methods are unable to meet the efficient heat dissipation and temperature control requirements of high heat flux electronic devices.Phase-change heat transfer,which utilizes the latent heat of vaporization to achieve efficient cooling,has become one of the main cooling methods for high heat flux electronic devices.According to the flow direction of the coolant and the working mode of the heat transfer surface,heat transfer modes can be divided into two major categories: horizontal flow and jet impingement.In the horizontal flow heat transfer mode,the flow direction of the coolant is parallel to the heat transfer surface,as seen in microchannel heat transfer.In the jet impingement mode,the flow direction of the coolant is perpendicular to the heat transfer surface.Previous studies have shown that coupling horizontal flow and jet impingement can significantly enhance the heat transfer performance of phase-change heat transfer devices.Based on this,this paper proposes and designs an innovative horizontal flow-jet impingement heat exchanger(HFJICHE)with submerged array jet columns.A horizontal flow-jet impingement boiling heat transfer experimental platform is constructed,and comparative experimental research is conducted using anhydrous ethanol as the coolant.The main research contents include:(1)The experimental research on the boiling heat transfer characteristics of the HFJICHE heat exchange device under the full horizontal flow mode,the full jet mode and the horizontal flow-jet coupling mode was carried out,focusing on the flow rate,heat flux density and the split ratio under the horizontal flow-jet impingement coupling conditions(Horizontal flow-jet impingement ratios(2:1,1:1,1:2)affect the heat transfer characteristics.It is found that there are two main heat transfer mechanisms in HFJICHE under different heat transfer conditions: nucleate boiling and forced convection.At flow rate,nucleate boiling is dominant,and at high flow rate,both nucleate boiling and forced convection dominate heat transfer characteristics;under the same heat flow and total flow rate,the heat transfer coefficient first decreases and then increases with the increase of jet impingement flow rate trend,and significantly increased CHF.(2)In order to further improve the boiling heat transfer performance of HFJICHE,this paper also proposes a multi-scale micro-nano composite structure based on copper-graphene and compares the boiling heat transfer with copper smooth heat transfer surface and array micro-needle fin heat transfer surface.Experimental studies have found that the surface of the copper-graphene multi-scale micro-nano composite structure can significantly increase the nucleation density of bubbles and improve the heat transfer coefficient under low heat flow conditions;Heating the dough and forming a vapor film reduces the CHF.(3)A visualization study was carried out on different flow heat transfer modes and boiling heat transfer on different heat transfer surfaces.It was found that the submerged array jet changes the position of the initial nucleation of the bubbles,and the bubble nucleation first occurs at a relatively low flow rate in the middle of the array jet column.In the area,and the array of jet columns can hinder the lateral merger of bubbles,delay the formation of steam film on the heat exchange surface,increase CHF,and at the same time have a disturbing effect on the two-phase fluid,and strengthen the two-phase convection effect.A large number of nucleated bubbles with smaller diameters are formed on the surface of the micronano composite structure under the condition of low heat flow,and the increase of the nucleated density of the bubbles is the main reason for the increase of the heat transfer coefficient.