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首页> 外文期刊>International Journal of Heat and Mass Transfer >Laminar mixed convection in an eccentric annular horizontal duct for a thermodependent non-Newtonian fluid
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Laminar mixed convection in an eccentric annular horizontal duct for a thermodependent non-Newtonian fluid

机译：偏心环形水平管道中的层流混合对流，用于非热依赖性的非牛顿流体

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摘要

The present work focuses on the study of mixed convection of a purely viscous shear-thinning fluid in a horizontal annular eccentric duct. The inner and outer cylinders are heated with constant and uniform heat flux densities. The objective of this work is to study the effect of the variation of eccentricity, rheo-logical behavior of the fluid as well as the thermodependency of the rheological parameters on the reorganization of the flow and thermal stratification caused by the buoyancy forces. At the entrance of the heating zone, the dynamic regime is assumed to be established and the temperature profile uniform. The conservation equations are solved numerically using a finite difference method with implicit schemes. A secondary azimuthal flow, induced by natural convection, develops downstream of the inlet section. This flow creates a stratification of the thermal field on a given section of the duct, which intensifies downstream from the entrance. On the other hand, the decrease in consistency with increasing temperature near the heated walls produces a centrifugal radial flow towards the walls. The presence of an eccentricity induces in turn a significant effect on the main dynamic field and the stratification of the thermal field. Two cases of upward and downward eccentricity are treated. These show that an upward shift increases the stratification of the thermal field, while the stratification begins to weaken from a certain amount of eccentricity in the case of downward shift. This represents an important result in terms of possible industrial applications. We may indeed conclude that an appropriate choice of downward eccentricity can reduce the thermal stratification, observed experimentally in the case of a concentric heated annular duct [1], when this stratification is undesirable. The choice of this eccentricity depends on rheological and thermal properties of the fluid.
机译：目前的工作重点是研究纯粘性剪切稀化流体在水平环形偏心管中的混合对流。内圆柱和外圆柱以恒定且均匀的热通量密度加热。这项工作的目的是研究偏心率变化，流体的流变行为以及流变参数的热依赖性对由浮力引起的流动重组和热分层的影响。在加热区的入口处，假定建立了动态​​状态，并且温度分布均匀。使用带有隐式格式的有限差分法对守恒方程进行数值求解。在自然的对流作用下，在进口段的下游形成了二次方位角流。这种流动在管道的给定部分上形成了热场分层，这加剧了入口的下游。另一方面，随着加热壁附近温度的升高，一致性的降低会产生朝向壁的离心径向流。偏心的存在反过来对主动态场和热场分层产生重大影响。处理了向上和向下偏心的两种情况。这些表明，向上移动增加了热场的分层，而在向下移动的情况下，分层从一定量的偏心率开始减弱。就可能的工业应用而言，这代表了重要的结果。我们确实可以得出这样的结论：当在同心加热的环形管道[1]的情况下不希望分层时，适当选择向下的偏心距可以减少热分层。偏心率的选择取决于流体的流变学和热学性质。

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