Magnetic field effect on laminar heat transfer in a pipe for thermal entry region
Magnetic field effect on laminar heat transfer in a pipe for thermal entry region
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磁场对热入口区域管道层流传热的影响
DOI：
10.1007/s12206-011-0140-6
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
M. Jahangiri
中科院分区：
文献类型：
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作者：
A. Malekzadeh;A. Heydarinasab;M. Jahangiri
实验研究了横向磁场对高普朗特数导电层流流过管道时局部换热的影响。实验表明局部努塞尔数增加。包含粘性和焦耳耗散项的运动方程和能量方程的耦合集变为非线性，并采用有限差分格式进行数值求解。与实验结果进行了比较，验证了数值计算结果的正确性。通过减小流动方向与磁场方向之间的夹角，可以减小磁场的影响。随着哈特曼数的增大，壁面温度降低，超过一定数值壁面温度降低速率减小。随着哈特曼数的增大，平均努塞尔数渐近于极限。此外，曲线拟合可以得到平均努塞尔数作为哈特曼数的函数的方程。这个方程类似于西德尔-塔特方程。观察到，增大哈特曼数对热边界层厚度没有显著影响，但会降低边界层内流体层的温度。
The influence of a transverse magnetic field on the local heat transfer of an electrically-conducting laminar fluid flow with high Prandtl number through a pipe was studied experimentally. Experiments indicated an increase in the local Nusselt number. The coupled set of the equations of motion and the energy equation including the viscous and Joule dissipation terms becomes non-linear and is solved numerically using a finite difference scheme. Favorable comparisons with experimental results confirm the correctness of the numerical results. It is found that the influence of magnetic field can be diminished by reducing the angle between the flow direction and the direction of magnetic field. The wall temperature reduces as the value of Hartmann number increases and the reduction rate of the wall temperature decreases as the value of Hartmann number exceeds a certain value. The average Nusselt number asymptotically approaches its limit as the Hartmann number becomes larger. Also, curve fitting can be employed to derive an equation for the average Nusselt number as a function of the Hartmann number. This equation is similar to the Sieder-Tate equation. It is observed that increasing the Hartmann number has no considerable effect on the thermal boundary layer thickness but decreases the temperature of fluid layers inside the boundary layer.