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首页> 外文期刊>Journal of Chemical Engineering >A Computational Study on Mixed Convection Heat Transfer in an Inclined Rectangular Channel under Imposed Local Flow Modulation
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A Computational Study on Mixed Convection Heat Transfer in an Inclined Rectangular Channel under Imposed Local Flow Modulation

机译：局部流动调节作用下斜矩形通道内混合对流换热的计算研究

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Numerical investigation of mixed convection heat transfer in an inclined 2D rectangular channel provided with partially heated bottom wall and a constant low temperature upper wall has been performed. The heated section of the bottom wall i.e. the heaters are maintained with constant heat flux and separated from each other by adiabatic segments. A fully developed parabolic velocity profile at constant low temperature is induced at the inlet. To enhance the heat transfer from the heaters, local flow field in the channel is modulated by placing circular cylinders rotating in counterclockwise direction (aiding flow) above each heater along the channel centerline. The fluid and the thermal fields within the rectangular channel are governed by the two-dimensional Navier-Stokes and Energy equations that have been solved by adapting Galerkin finite element method. The governing parameters of the present problem such as Reynolds number ( Re ) and Grashof number ( Gr ) are varied in the range of 1 ≤ Re ≤ 100 and 10 3 ≤ Gr ≤ 10 5 . Air has been considered as working fluid having a Prandtl number, Pr = 0.71. In addition to these governing parameters, the inclination angle of the channel ( α ) and the speed ratio ( ξ ) that is the ratio of peripheral speed of the rotating cylinder and the maximum inlet flow velocity is also varied in the range of 0 ° ≤ α ≤ 90 ° and 0.5 ≤ ξ ≤ 2.0 respectively. The thermal and the fluid fields are visualized via the isotherm and the streamline plots. The efficacy of local flow modulation with rotating cylinder for heat transfer enhancement has been estimated in terms of normalized average Nusselt number over the heaters as Nu/Nu nc , where Nu and Nu nc represents the average Nusselt number with and without flow modulation respectively. Results obtain in the present study reveals that, for very weak flow (Re = 1), flow modulation results in lower heat transfer particularly at lower values of Gr on the contrary for moderate and higher values of Re (10, 100), flow modulation has been found to result in higher heat transfer particularly at lower values of Gr . For example, at Re = 100 and α = 0 ° , about 32% to 55% enhancement in heat transfer has been obtained for 10 3 ≤ Gr ≤ 105. Variation in heat transfer enhancement through flow modulation has also been noticed for different channel inclination angle ( α ) for various system configurations. Journal of Chemical Engineering, Vol. 30, No. 1, 2017: 43-50
机译：已经进行了在具有部分加热的底壁和恒定的低温上壁的倾斜的二维矩形通道中混合对流传热的数值研究。底壁的加热部分，即加热器保持恒定的热通量，并通过绝热段彼此隔开。在入口处产生了在恒定的低温下完全展开的抛物线速度曲线。为了增强来自加热器的热量传递，通过将沿逆时针方向旋转（辅助流动）的圆柱体沿着通道中心线置于每个加热器上方，来调节通道中的局部流场。矩形通道内的流体和热场由二维Navier-Stokes和Energy方程控制，该方程已通过采用Galerkin有限元方法求解。当前问题的控制参数，例如雷诺数（Re）和格拉斯霍夫数（Gr）在1≤Re≤100和10 3≤Gr≤10 5的范围内变化。空气被认为是具有Prandtl值Pr = 0.71的工作流体。除了这些控制参数外，通道的倾斜角度（α）和速比（ξ）也在0°≤范围内变化，速比是旋转气缸圆周速度与最大入口流速之比。 α≤90°和0.5≤ξ≤2.0。通过等温线和流线图可视化热场和流场。已经根据加热器上的归一化平均努塞尔数（Nu / Nu nc）估算了带有旋转圆柱体的局部流量调制对增强传热的功效，其中Nu和Nu nc分别表示有和没有流量调制的平均努塞尔数。在本研究中获得的结果表明，对于非常弱的流量（Re = 1），流量调节会导致较低的传热，尤其是在Gr的值较低时，相反，对于中等和较高的Re（10，100）值，流量调节已经发现特别是在较低的Gr值下导致较高的热传递。例如，在Re = 100且α= 0°时，对于10 3≤Gr≤105，可获得约32％至55％的传热增强。对于不同的通道倾角，通过流量调节的传热增强也有所不同。各种系统配置的最大角度（α）。化学工程杂志，卷。 2017年1月30日：43-50

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