Study On Heat Transfer Characteristics Of Single Phase And Flow Boiling In Copper-based Minichannel Heat Sink

With the development of aerospace industry and mainframe servers,VLSI(vast large scale integrated)chips appear later.Heat value of integrated circuits is increasing rapidly.The number of integrated transistors in unit area of chip increases manifold,from thousands to billions.Therefore,solving heat dissipation issues in microelectronic devices become more and more important.The traditional refrigeration technology has strict demands in material and space.So it can't meet the growing demand of heat dissipation of chips.In this paper,a novel minichannel heat sink is designed and experimentally investigated the flow boiling performance to solve heat dissipation problems in chips.The minichannel heat sinks is studied systematically by a minichannel heat transfer platform.The test section is designed and fabricated,and a series of processes is quested,including fabrication,sealing,cleaning,vacuuming,outgassing,and injecting nitrogen.Acetone is working fluid.Experiments are studied heat fluxes,mass fluxes,inlet temperature and channel stricture's influence on fluid flow and heat transfer performance.Flow boiling instabilities of two minichannels are studied.Firstly,the flow boiling performance in the straight minichannels had been studied experimentally.The results showed as follows:In the low and middle mass flux region(5.48 kg/(m~2·s)~14.25 kg/(m~2·s)),the boiling process was dominated by forced connective boiling mechanism.In the high mass flux region(16.45 kg/(m~2·s)~19.74kg/(m~2·s)),the nucleate boiling mechanism controlled the heat transfer process in the minichannel.The flow pattern change through flow visualizations.Secondly,the flow boiling performance in the semi-open minichannels had been studied experimentally.The results showed as follows:In the low mass flux region(4.34kg/(m~2·s)~8.68 kg/(m~2·s)),the boiling process was dominated by forced connective boiling mechanism.In the middle mass flux region(11.28 kg/(m~2·s)~13.12kg/(m~2·s)),the heat transfer process was dominated by the mixture boiling mechanism.In the high mass flux region(15.62 kg/(m~2·s)and above),the nucleate boiling mechanism controlled the heat transfer process in the minichannel.The semi-open minichannels presented a better heat transfer characteristics than straight minichannels in low or middle mass fluxes.And the straight minichannels had a similar heat transfer characteristics to that of the semi-open minichannels in high mass fluxes.The semi-open minichannels embodied more stable fluctuation of inlet pressure than the straight minichannels,because of the minichannel's structure.Thirdly,using CFD carried on the numerical simulation of the single-phase flow and heat transfer of the semi-open minichannels and the straight minichannels.The results showed as follows:the flow velocity in straight minichannel heat sink was faster than the flow velocity in semi-open minichannel heat sink,because there is an opening space in the semi-open minichannel heat sink.In temperature distribution,the average temperature of straight minichannel heat sink was lower than the average temperature of semi-open minichannel heat sink.Nu of the straight minichannels was slightly larger than Nu of the semi-open minichannels.Totally,the straight minichannels had better heat transfer characteristics than the semi-open minichannels in single-phase flow.