Study On Heat Dissipation Characteristics Of CPU Based On Coupled Cooling Of Nanofluids And Enhanced Heat Transfer Surface

In recent years,with the rapid development of electronic technology,the high frequency and high speed of electronic devices,and the intensive and miniaturization of integrated circuits have led to a sharp increase in the heat generation per unit size of the CPU?Central Processing Unit?.The processing speed of the CPU is closely related to the temperature.If the CPU temperature rises by 1°C,its performance will drop by 5%.Therefore,designing and manufacturing an efficient CPU heat sink becomes an urgent problem which needs to be solved.Traditional cooling fluids?water,air,oil,etc.?are no longer able to meet such high-intensity heat dissipation requirements.As a new type of cooling fluid,nanofluids have high thermal conductivity and good heat transfer performance,and they are widely used in scientific research and industrial fields.Based on above research background,this thesis mainly studies from two aspects:on the one hand,nanofluids with high thermal conductivity are used as CPU cooling mediums;on the other hand,grooves and bulges are used to change the heat transfer surface of CPU heat sink to improve the thermal performance.The main research contents and results of this paper are summarized as follows:?1?Different mass fractions of TiO₂-H₂O nanofluids?0.1%-0.5%?are prepared by“two-step method”,and the stability and thermal properties of the prepared nanofluids are studied and analyzed.?2?The cooling performance of nanofluids in CPU heat sinks with different heat transfer surfaces are experimentally studied.The heat transfer surfaces are changed by hemispherical bulges,rectangular grooves,cylindrical bulges,and cylindrical grooves.The effects of the arrangements of hemispherical bulges?aligned arrangement,staggered arrangement?,the depths of rectangular grooves?1mm,2mm?,the arrangements of cylindrical bulges?aligned arrangement,staggered arrangement?,the arrangements of cylindrical grooves?aligned arrangement,staggered arrangement?and the depths of cylindrical grooves?1mm,2mm,3mm?on the heat transfer and flow characteristics of the nanofluids in the CPU heat sink are studied.Lastly,a variety of evaluation criterias,such as comprehensive evaluation index,thermal efficiency,exergy efficiency,entropy generation,are applied to analyze the cooling performance of nanofluids in different structure heat sinks.The results show that nanofluids can effectively reduce the CPU temperature as a cooling medium.The surface temperatures of CPU cooled by nanofluids with aligned arrangement and staggered arrangement can be reduced by 10.5%and 12.5%at best compared with water respectively.CPU surface temperatures with staggered arrangement can be reduced by 2.7-3.8%compared with aligned arrangement.For different enhanced heat transfer structures,the cooling performance of TiO₂-H₂O nanofluids increases first and then decreases with the increasing mass fraction,and there is always a mass fraction to make the nanofluids exhibit the best heat transfer performance.For bulges structure and grooves structure,the best mass fractions are0.4%and 0.3%respectively.The thermal efficiency of the cylindrical grooved heat sink decreases with the nanoparticle mass fraction,but increases with the groove depth.Under the same enhanced heat transfer technology,the thermal efficiency of the aligned structure is higher than that of the staggered structure.The exergy efficiency of the cylindrical grooved heat sink is significantly improved at the same pump work and flow rate.For cylindrical grooved heat sink,the total entropy generation of the staggered structure is almost twice that of the aligned structure,which indicates that the aligned structure has better entropy generation performance during heat transfer process.