Intermittent High Power Phase Change Heat Sink Research

Conventional heat dissipation methods such as air-cooling and liquid-cooling often have complicated systems,large size,as well as high maintenance cost when faced with IGBT,power battery and outdoor radars.Using phase change material for thermal control instead could not only perfectly avoid the problems mentioned above,but also effectively solve the problem of thermal shock which exists in electronics during startup.However,most research focused on using phase change material for thermal management is limited to a small heat dissipation power,which results in failure to meet the demands of military,aviation,aerospace as well as industry.Therefore,a heat exchanger capable of handling a high heat dissipation rate of 300 W was built,which selects paraffin as phase change medium and uses fin as heat conduction reinforcement.For the whole research content,there are mainly four parts included.Firstly,experiments were carried out to test the thermal properties of paraffin wax,including thermal conductivity,phase transition temperature,latent heat as well as specific heat capacity.And it was divided into two parts for research: 1)Experimental study of thermal conductivity.In view of the low thermal conductivity of paraffin,expanded graphite was introduced as the thermal conductive filler to enhance the heat transfer performance of paraffin wax No.56.Composites that consists of expanded graphite and paraffin wax No.56 were prepared to investigate the effect of mass ratio of expanded graphite on thermal conductivity.2)Experimental study of phase transition temperature,latent heat of phase change and specific heat capacity.In order to study the effect of the mass ratio of expanded graphite on the physical properties of the composite above,the expanded graphite-56 paraffin samples with different mass ratios were prepared and measured by PerkinElmer Diamond DSC.Secondly,the heat exchanger design was conducted and the details are as follows.9wt% EG-paraffin composite material is selected as the phase change medium.In order to reduce expenses,the fin and the package shell were separately fabricated and screwed.And the initial structure of the heat exchanger was determined by fluent software which applied a mathematical model of the equivalent specific heat capacity.Thirdly,in order to investigate the influence of phase change medium on the temperature control performance of the heat exchanger and verify the reliability of the mathematical model,a testing system including a stainless steel mica electric heating plate,DC power supply,Agilent data acquisition system,heat exchanger,T type thermocouple and desktop computer were built.Last but not least,the structure of the heat exchanger is optimized by using the same numerical method and phase change material.After optimization,the newly designed heat exchanger can work stably for at least 1800 s under the condition of heat source power of 300 W and safe temperature of 338 K,but its cost is only 3,500 yuan,and the overall weight of the device is only 4.58 Kg.The heat pipe phase change heat sink designed further can work stably for 4300 s under the same conditions as above,and the internal temperature difference of the system is only 1.6K,and the temperature control performance is better.