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首页> 外文期刊>International Journal of Heat and Mass Transfer >Heat transfer coefficients from Newtonian and non-Newtonian fluids flowing in laminar regime in a helical coil
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Heat transfer coefficients from Newtonian and non-Newtonian fluids flowing in laminar regime in a helical coil

机译：螺旋层流中层流状态下的牛顿流体和非牛顿流体的传热系数

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摘要

This study aimed to carry out experimental work to obtain, for Newtonian and non-Newtonian fluids, heat transfer coefficients, at constant wall temperature as boundary condition, in fully developed laminar flow inside a helical coil. The Newtonian fluids studied were aqueous solutions of glycerol, 25%, 36%, 43%, 59% and 78% (w/w) and the non-Newtonian fluids aqueous solutions of carboxymethylcellulose (CMC), a polymer, with concentrations 0.1%, 0.2%, 0.3%, 0.4% and 0.6% (w/w) and aqueous solutions of xanthan gum (XG), another polymer, with concentrations 0.1% and 0.2% (w/w). According to the rheological study performed, the polymer solutions had shear thinning behavior and different values of elasticity. The helical coil used has internal diameter, curvature ratio, length and pitch, respectively: 0.004575 m, 0.0263, 5.0 m and 11.34 mm. The Nusselt numbers for the CMC solutions are, on average, slightly higher than those for Newtonian fluids, for identical Prandtl and generalized Dean numbers. As outcome, the viscous component of the shear thinning polymer tends to potentiate the mixing effect of the Dean cells. The Nusselt numbers of the XG solutions are significant lower than those of the Newtonian solutions, for identical Prandtl and generalized Dean numbers. Therefore, the elastic component of the polymer tends to diminish the mixing effect of the Dean cells. A global correlation, for Nusselt number as a function of Peclet, generalized Dean and Weissenberg numbers for all Newtonian and non-Newtonian solutions studied, is presented.
机译：这项研究旨在开展实验工作，以在恒定壁温作为边界条件的条件下，在螺旋盘管内部充分展开的层流中获得牛顿和非牛顿流体的传热系数。所研究的牛顿流体是25％，36％，43％，59％和78％（w / w）的甘油水溶液以及羧甲基纤维素（CMC）（一种浓度为0.1％的聚合物）的非牛顿流体水溶液。 ，0.2％，0.3％，0.4％和0.6％（w / w）以及另一种浓度为0.1％和0.2％（w / w）的聚合物黄原胶（XG）的水溶液。根据进行的流变学研究，聚合物溶液具有剪切稀化行为和不同的弹性值。所使用的螺旋线圈的内径，曲率比，长度和节距分别为：0.004575 m，0.0263、5.0 m和11.34 mm。对于相同的Prandtl和广义Dean数，CMC解决方案的Nusselt数平均略高于牛顿流体的Nusselt数。结果，剪切稀化聚合物的粘性组分倾向于增强迪安细胞的混合效果。对于相同的Prandtl和广义Dean数，XG解决方案的Nusselt数显着低于Newtonian解决方案的。因此，聚合物的弹性成分趋向于降低迪安细胞的混合效果。提出了Nusselt数与Peclet的函数的全局相关性，研究了所有牛顿和非牛顿解的广义Dean和Weissenberg数。

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