同心双扭旋元件管ZrO_(2)-水纳米流体的传热特性

Heat transfer characteristics of concentric double-twisted element tube with ZrO_(2)-water nanofluid

为探究纳米流体对内置同心双扭旋元件圆管传热特性的影响规律,采用浓度不同的ZrO2-水纳米流体对Re=200-1200范围内恒壁温条件下的管内传热进行了数值模拟分析.同时采用单相流与两相流模型结果与实验数据进行对比.结果表明:两相流模型更符合纳米流体在同心双扭旋元件换热管的数值模拟分析;以ZrO2-水纳米流体为工质的同心双扭旋元件换热管的换热效果明显优于水,且浓度越高,传热效果越佳,Nu相对于水在光管的强化幅度为5.34倍;但纳米流体浓度越高,阻力系数也越大,但相差不大,最大仅相差7%;同心双扭旋元件换热管中ZrO2-水纳米流体的浓度越高,换热管的综合传热性能评价因子(PEC值)越大,最大值为1.53.

In order to investigate the effect of nanofluids on the heat transfer characteristics of circular tubes with concentric double-twisted elements,the ZrO2-water nanofluids with different concentrations were used to calculate the heat transfer in the tubes at constant wall temperature in the range of Re=200-1200 by simulation analysis.The results of single-phase and two-phase flow models are compared with experimental data.The results show that the two-phase flow model is better with the numerical simulation analysis of nanofluids in concentric double-twisted element heat transfer tubes;the concentric double-twisted element heat transfer tube with ZrO2-water nanofluid as the working medium is obviously better than water,and the higher the concentration,the better the heat transfer effect.The strengthening amplitude of Nu is 5.34 times than water in the plain tube;however,the higher the concentration of the nanofluid,the larger the coefficient of resistance,but the difference is not large.The maximum difference is only 7%;The higher the concentration of ZrO2-water nanofluid in the concentric double-twisted element heat exchange tube,the greater the heat transfer performance evaluation factor(PEC value)of the heat exchange tube,with a maximum value of 1.53.