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测量了3种不同粒径(23、51和76nm)的CuO-水纳米流体在层流状态下的管流对流换热系数,对比不同纳米颗粒粒径对层流区对流换热的影响。实验结果表明,在液体中添加纳米粒子增大了液体的管内对流换热系数,且在相同雷诺数条件下,23nm粒径的纳米流体对流换热系数要比其他2种粒径的纳米流体对流换热系数高出大约10%。基于有效介质理论和分型理论,得出新的纳米流体有效导热系数关联式,使用此关联式计算对流换热系数能够得到更加精确的实验方程。
The convective heat transfer coefficients of three kinds of CuO-water nanofluids with different particle sizes (23, 51 and 76 nm) under laminar flow were measured. The influence of different nanoparticle size on the convective heat transfer in the laminar flow region was compared. The experimental results show that adding nano-particles to the liquid increases the convective heat transfer coefficient of the liquid in the liquid, and the convective heat transfer coefficient of the nanofluid with the diameter of 23 nm is more than that of the nanofluid with the other two particle sizes under the same Reynolds number conditions The heat transfer coefficient is about 10% higher. Based on the theory of effective medium and the theory of classification, a new correlation equation of effective thermal conductivity of nanofluids is obtained. Using this correlation formula to calculate the convective heat transfer coefficient, a more accurate experimental equation can be obtained.