Numerical investigation of laminar heat transfer and nanofluid flow between two porous horizontal concentric cylinders

Abstract

In this study, the laminar heat transfer and nanofluid flow between two porous horizontal concentric cylinders was investigated. The problem is investigated in two different geometries and the Re=10, 25, 50, 75, 100 and volume fraction 0, 0.2%, 0.5%, 2% and 5% that related to copper nanoparticles, and porous medium porosity of 0.5 and 0.9. Compared to the first geometry, the convective coefficient in the second geometry increases by 8.3%, 7% and 5.5% at Reynolds numbers of 100, 75 and 50, respectively. Comparison of the outlet temperatures for two heat fluxes of 300 and 1200 W/m² indicates a 2.5% temperature growth by a fourfold increase in the heat fluxes. Also, the higher Nusselt number is associated with the second geometry occurring at porosities of 0.9 and 0.5, respectively. In both geometries, the Nusselt number values at the porosity of 0.9 are higher, which is due to the increased nanofluid convection at higher porosities. The velocity of the nanofluid experiences a two-fold increase at the outlet compared to its inlet velocity in the first geometry and for both porosities. Similarly, a three-fold increase was achieved in the second geometry and for both porosities.

摘要

研究了在Re=10, 25, 50, 75, 100 和铜纳米粒子体积分数分别为0, 0.2%, 0.5%, 2%和5%, 多孔介质孔隙率分别为0.5 和0.9 条件下多孔水平同心圆柱间的层流传热和纳米流体流动。在雷诺数 分别为100、75 和50 时, 与第一种几何形式相比, 第二种几何形式的对流系数分别增加了8.3%、7% 和5.5%。对300 和1200 W/m² 两种热通量的出口温度进行比较, 发现热通量增加4 倍, 温度增加了 2.5%。此外, 较高的Nusselt 数与第二种几何形状相关, 分别出现在0.9 和0.5 的孔隙度。在这两种几 何结构中, 孔隙度为0.9 时的Nusselt 数值较高, 这是由于孔隙度较高时纳米流体对流增加所致。在第 一几何形状和孔隙度下, 纳米流体的出口的速度比进口速度增加2 倍。同样, 在第二个几何图形和两 个孔隙度上都实现3 倍的增长。