换热器内纳米流体换热与压降特性的分析

Analysis of Heat Transfer and Pressure Drop Characteristics of Nanofluids in Heat Exchanger

以人字形板式换热器翅片的单元流道二维截面为几何模型,采用Fluent软件对换热介质分别为水、水基Al2O3纳米流体和水基CuO纳米流体进行换热、压降特性的数值分析,结果表明:在水中添加纳米颗粒可以提高流体的换热能力,且随着纳米颗粒体积分数的增加,努塞尔数随之增大,同时,纳米颗粒体积分数为3.0%时,流体对应的努塞尔数增幅明显高于1.0%~2.0%的水基Al2O3纳米流体。但结果还表明,纳米颗粒体积分数为3.0%的水基Al2O3纳米流体对应的压降最高,不利于流体流动,因而在将纳米流体作为流动换热介质时,应该综合考虑换热与压降的影响。另外,在相同纳米颗粒体积分数以及入口雷诺数时,水基Al2O3纳米流体换热能力高于水基CuO纳米流体,但两者的流动压降几乎相同,因而应优先选用Al2O3纳米颗粒。由于目前将纳米流体与换热器相结合的相关研究较少,因而得出数值结论对纳米流体在换热器中的应用设计具有一定的参考意义。

Taking the two-dimensional cross section of unit channel of the fin of V-shape corrugated plate heat exchanger as the geometric model,the heat transfer and pressure drop characteristics of water,water-based Al2O3 nanofluids and water-based CuO nanofluids were analyzed respectively by FLUENT software.The results show that the heat transfer capacity of the fluid can be improved by adding nanoparticles into the water,and the Nusselt number increases with the increase of the volume fraction of nanoparticles.At the same time,when the volume fraction of nanoparticles is 3.0%,the increase of Nusselt number of the fluid is significantly higher than that of the water-based Al2O3 nanofluids,which is 1.0%~2.0%.However,the results also show that the water-based Al2O3 nanofluids with a 3.0%volume fraction of nanoparticles has the highest pressure drop,which is not conducive to the flow of the fluid.Therefore,when nanofluid is used as the flow and heat transfer medium,the influence of heat transfer and pressure drop should be considered comprehensively.In addition,the heat transfer capacity of water-based Al2O3 nanofluids is higher than that of water-based CuO nanofluids at the same volume fraction of nanoparticles and inlet Reynolds number,but their flow pressure drops are almost the same,so Al2O3 nanoparticles should be selected preferentially.At present,there are few researches on the combination of nanofluids with heat exchanger,so the numerical conclusions can be used as reference for the application of nanofluids in heat exchanger.