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采用数值模拟的方法研究了矩形腔内Cu O-H2O纳米流体自然对流的换热特性和换热机理。重点分析了二维封闭腔内不同Ra数下,纳米颗粒体积分数和粒径对Cu OH2O纳米流体自然对流时温度场和速度场的影响,并探讨了纳米颗粒布朗运动对换热的影响。数值模拟结果表明:对于给定的Ra数,随着体积分数的增大和颗粒粒径的减小,纳米流体的换热效果会显著增强;当Ra数较小时,换热形式主要表现为热传导,随着Ra数的增大,换热形式逐渐变为以热对流为主;纳米颗粒布朗运动是影响纳米流体换热的重要因素,随着布朗运动的增强,纳米流体内部的能量传递增强,从而使换热增强。
The heat transfer characteristics and heat transfer mechanism of natural convection of Cu O-H2O nanofluids in rectangular cavity were studied by numerical simulation. The effects of nanoparticle volume fraction and particle size on the temperature field and velocity field at natural convection of CuOH2O nanofluids at different Ra numbers in a two-dimensional closed cavity were analyzed. The effects of Brownian motion of nanoparticles on heat transfer were also discussed. Numerical simulation results show that for a given Ra number, the heat transfer efficiency of nanofluids can be significantly enhanced with the increase of volume fraction and particle size reduction. When the Ra number is small, the heat transfer forms are mainly heat conduction, With the increase of Ra number, the form of heat transfer becomes predominantly convection; the Brownian motion of nanoparticles is an important factor that affects the heat transfer of nanofluids. With the enhancement of Brownian motion, the energy transfer within nanofluids is enhanced, Make heat exchange enhanced.