| With the sharp increase in performance,thermal issue becomes one of the main factors limiting the development of electronic devices.If heat dissipation is not good,high temperature will be generated in elelctronic devices,affecting the performance and even leading to device failure.With the increase of integration,the power density and the heat flux of the device increases greatly.High heat flux leads to heat accumulation,resulting in high temperature,which is harmful to electronic devices.At present,however,there are not enough thermal management methods to achieve efficient heat dissipation of electronic devices with high heat flux.In addition,as for some devices with local high heat flux hot-spot,there is a lack of efficient heat dissipation methods that is aiming at temperature uniformity for decreasing the local high temperature.In view of the above problems,following research studies are included in this dissertation:A distributed jet array impingement body cooling structure was presented.The coolant was ejected through the array nozzles and impinged onto all the available surfaces of the heated chip,making the heat dissipation area of the chip taken fully advantage of.The coolant contacted the chip surface directly,resulting in decreasing thermal resistance.The distributed returns were arranged between the adjacent nozzles to reduce the interaction between the fluid ejected by the adjacent nozzles.The heat and flow performance of the presented structure was studied by numerical simulation and experiments.It was found that the body cooling not only can take fully advantage of the heat transfer area of the chip,but also can make use of the three-dimensional heat conduction of the chip.It made the coolant more close to the heat source,leading to further dereasing of the total thermal resistance.The tested total thermal resistance was only 0.05K/W when the volume flow rate was 2100mL/min.An immersed jet array impingementbody cooling structure was presented,which is able to withstand higher temperature and is more reliable.By decreasing the nozzle diameter,the presented structure presented better cooling performance than the distributed jet array impingement body cooling device.Thermal resistance optimization and improvement design were done to the thermal test section,to make it realize 440W/cm~2 high heat flux and 2200W high thermal power heat source.The heat loss of the thermal test section is only 1.2%.The high-power liquid cooling performance test system was established and tests were done to the presented heat sink device.Experimental results showed that,the overall thermal resistance of the heat sink doesn't change with the heating power of the chip,and the chip temperature changes linearly with the heating power.The total thermal resistance of the device was only 0.0318K/W when the volume flow rate was 5L/min,which is even lower that the bulk thermal resistance 0.0333K/W of the thermal interface material.The hybrid body cooling method was provided.And the three-dimensional heat transfer models were establish for the immersed jet array impingement body cooling(JIBC),hybrid body cooling(HBC)and the traditional jet array impingement single-surface cooling(JISC).The established models were verified by simulation and experiment.The discrepancy was only less than 10.8%,21%and 19%for JIBC,HBC and JISC,respectively,indicating that the three models is useful to the initial design of the corresponding liquid cooling method.The flow and heat transfer characteristics of the three liquid cooling methods were studied by model and simulation.The results showed that,the HBC might have better heat dissipation performance than the JIBC with some certain chip size,structure of the heat sink and parameters of the jet array.In this case,the convective heat transfer coefficient of the HBC on the top surface of the chip should be obviously higher than that of the JIBC.The convective heat transfer coefficient of the HBC on the side surfaces of the chip should not have much difference with that of the JIBC.The global refined microchannel structure was presented.The surface temperature difference of the chip caused by the local high heat flux hot-spot and the temperature rise of the coolant was reduced by the presented structure.In addition,the corresponding bi-layer compact 3D thermal model for the microchannel was established.The model was validated by COMSOL simulation and the discrepancy was only less than 4.8%.Therefore,the proposed model was able to accurately predict the chip surface temperature field when the heat source and the witdh of the microchannel are both non-uniform.We studied the heat transfer process by using the proposed thermal model.Results show that,although local convective heat transfer coefficient can be enhanced by refining the microchannel,the local chip temperature might be higher than before because of the flow rate reduction.Finally,based on the proposed thermal model,the global refined microchannel was optimal designed by genetic algorithm.The optimized microchannel made the maximum temperature difference of the chip surface reduced from 45?to 13?,presenting good temperature uniformity. |
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