Effects of radiation and magnetic field on mixed convection stagnation-point flow over a cylinder in a porous medium under local thermal non-equilibrium
Effects of radiation and magnetic field on mixed convection stagnation-point flow over a cylinder in a porous medium under local thermal non-equilibrium
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DOI：
10.1007/s10973-019-08415-1
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发表时间：
2019-06
影响因子：
4.4
通讯作者：
Rasool Alizadeh;N. Karimi;A. Nourbakhsh
中科院分区：
文献类型：
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作者：
Rasool Alizadeh;N. Karimi;A. Nourbakhsh
研究了纳米流体驻点绕多孔介质圆柱流动的传热强化和熵产。圆柱外表面存在非均匀发汗。采用半相似技术数值求解多孔介质中流动与传热的三维动量方程和两方程热能输运模型。该数学模型考虑了多孔介质中的非线性热辐射、磁流体动力学、混合对流和局部热非平衡等因素。纳米流体和多孔固体的温度场以及Bejan数的可视化，和周向平均努塞尔数的值的报告。结果表明，热辐射对温度场有显著影响，从而影响努塞尔数和贝扬数。一般来说，更多的辐射系统具有较高的努塞尔数和较少的热不可逆性。它还表明，在毕奥数的数值变化可以大大修改努塞尔数的预测值和局部热平衡模型可能显着低估努塞尔数。然而，磁力对传热速率的影响不大。然而，它们可以显着增加摩擦不可逆性，从而降低贝扬数的值。值得注意的是，目前的工作是第一个系统的分析驻点流在弯曲的配置，包括非线性热辐射和局部热不平衡。
Heat transfer enhancement and entropy generation are investigated in a nanofluid, stagnation-point flow over a cylinder embedded in a porous medium. The external surface of cylinder includes non-uniform transpiration. A semi-similarity technique is employed to numerically solve the three-dimensional momentum equations and two-equation model of transport of thermal energy for the flow and heat transfer in porous media. The mathematical model considers nonlinear thermal radiation, magnetohydrodynamics, mixed convection and local thermal non-equilibrium in the porous medium. The nanofluid and porous solid temperature fields as well as those of Bejan number are visualised, and the values of circumferentially averaged Nusselt number are reported. The results show that thermal radiation significantly influences the temperature fields and hence affects Nusselt and Bejan number. In general, more radiative systems feature higher Nusselt numbers and less thermal irreversibilities. It is also shown that changes in the numerical value of Biot number can considerably modify the predicted value of Nusselt number and that the local thermal equilibrium modelling may significantly underpredict the Nusselt number. Magnetic forces, however, are shown to impart modest effects upon heat transfer rates. Yet, they can significantly augment frictional irreversibility and therefore reduce the value of Bejan number. It is noted that the current work is the first systematic analysis of a stagnation-point flow in curved configurations with the inclusion of nonlinear thermal radiation and local thermal non-equilibrium.