Study On Heat Transfer Characteristics Of Compact Micro Spray Cold Plate

With the continuous development of electronic components integration,the power density of electronic components continues to increase,and the problems faced by thermal management of components are becoming more and more serious.In the fields of radar,laser,data center,etc.,due to the high of heat flux and multi-heat source devices in a compact space,conventional liquid-cooled cold plate have been unable to meet the thermal control requirements of high-power,high-integrated electronic components.Exploring new thermal control methods to meet the heat demand of compact space and high heat flux,and improving thermal control accuracy and meeting temperature uniformity requirements is a key issue that needs to be solved urgently.Spray cooling has broad potential application prospects in high heat flux thermal control due to its advantages of high heat dissipation,low flow demand and fast temperature control response.In order to solve the problem of high heat flux and multi-heat source heat dissipation in compact space,this thesis proposes a new compact micro spray cold plate which combined with spray cooling high heat flux technology and liquid-cooled cold plate structure.Through the performance analysis,prototype trial and experimental research and combined with the practical application prospects,the heat transfer characteristics of the compact micro spray cold plate were systematically studied.In this thesis,the heat transfer characteristics of liquid-cooled cold plates were experimentally studied.The effects of different strengthening structures of micro-channels on the heat transfer characteristics of cold plates were studied,the influence of key parameters is obtained.The research results show that the pin-ribbed reinforced structure is superior to the straight rib-type reinforced structure,and the heat transfer performance is improved by 29.4%,and the temperature uniformity of the heat-generating surface is also improved;for the same type of reinforced structure,the smaller the rib spacing,the better the heat transfer effect;as the volume flow increases,the heat transfer effect is improved,and the flow resistance is also increased.Therefore,it is necessary to determine the appropriate flow rate according to the needs of the actual application.In order to further improve the heat transfer characteristics of the liquid-cooled cold plate,this thesis proposes a new compact micro spray cold plate to solve the heat dissipation problem of high heat flux multi-heat source.The simulation process of the spray process of micro-nozzle and the heat transfer process of micro spray cold plates was carried out.The analysis results of the micro-nozzle spraying process show that the nozzle flow rate and flow resistance increase with the nozzle inlet pressure as the nozzle swirl chamber opening angle is the same,and the spray opening angle increases rapidly with the increase of the flow rate,and then remain basically unchanged;under the same inlet pressure,the flow rate decreases with the increase of the opening angle of the nozzle swirling chamber,and the flow resistance increases with the increase of the opening angle of the swirling chamber.The nozzle flow rate and flow resistance increase with the increase of the nozzle outlet diameter.The simulation results of the compact micro spray cold plate show that at a single nozzle flow rate of 5.0 L/h,the heat dissipation capacity of 300 W/cm2 can be achieved,and the maximum temperature difference between multiple heat sources can be achieved,and the maximum temperature difference between multiple heat sources is 6.1?.The analysis results show that the micro spray cold plate proposed in this thesis has good thermal control effect on high heat flux multi-heat source.Based on the simulation analysis,this thesis prototyped a compact micro spray cold plate sample and built an experimental system of micro spray cold plate,with water and glycol coolant as the working medium,the heat transfer characteristics of the cold spray plate under normal working conditions and vibrating conditions were studied experimentally,and the influence of the cooling curve and its controllable parameters on the heat transfer characteristics was obtained.The results show that the heat transfer effect of water as working medium is better than that of ethylene glycol aqueous solution,and the heat transfer effect of compact micro spray cold plate increases with the increase of flow rate,but the rate of increase gradually slower,and the increase of flow means the increase of pumping power,which indicates that the compact micro spray cold plate has certain limitations in improving the heat dissipation performance by increasing the flow rate in practical applications;the heat dissipation capacity of the compact micro spray cold plate with water as the working medium exceeds 300W/cm2,and the maximum temperature difference between multiple heat sources does not exceed 6.5?,which indicates that the novel micro spray cold plate has good heat dissipation capacity while achieving good heat dissipation and temperature uniformity;the angle between the placement direction of the compact micro spray cold plate and the gravity direction has a certain influence on the heat dissipation characteristics.When the placement direction is consistent with the gravity direction,better heat dissipation is caused by better drainage;because the vibration has a certain strengthening effect on the disturbance of the liquid film in the cavity,compared with the steady state condition,the compact micro spray cold plate exhibits better heat dissipation characteristics under the triaxle vibration condition,wherein the Z(gravity)directional vibration is the most obvious improvement of the heat transfer effect of the compact micro spray cold plate.In order to further reduce the volume of the compact micro spray cold plate,the design scheme of the micro spray cold plate using the piezoelectric ceramic atomizing nozzle is proposed in this thesis.The spray effect is generated by the self-vibration of the piezoelectric atomizing nozzle,and the corresponding samples were developed and experimentally studied.The results show that the heat flux of 189.6W/cm2 can be achieved by a single piezoelectric atomizing nozzle with a flow rate of 7mL/min,and the temperature difference between the heat sources is 8.6?.The thermal effect is affected by the flow rate and the spray height,as the flow rate increases,the heat transfer effect increases,and the temperature uniformity of multiple heat sources also increases,and there is an optimal spray height.