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Numerical simulation of the heat transfer process of a coiled tube for viscous fluids
Case Studies in Thermal Engineering ( IF 6.8 ) Pub Date : 2022-06-20 , DOI: 10.1016/j.csite.2022.102186
D. Sánchez , J.A. Almendros-Ibáñez , A. Molina , F. Bozzoli , L. Cattani , J.I. Córcoles

This study presents the results of a numerical simulation in a helical coiled tube for Newtonian and non-Newtonian fluids in laminar regime. As a practical contribution, the numerical simulations use non-Newtonian fluids, the rheological properties of which are experimentally measured.

In both non-Newtonian fluids, at the helical section, the heat transfer rate was higher than that at the straight section. For the fruit juice, the heat transfer coefficient (hw) reached values of 1000 and 1350 W/m2 K at the coil, which were 73% and 126% higher than in the straight section, for an Reg of 255 and 634, respectively. For the carboxyl methyl cellulose solution, these differences ranged between 76% (Reg = 255) and 210% (Reg = 634), reaching hw values at the coil of 1950 and 2700 W/m2 K.

In all non-Newtonian cases, fluid mixing was improved at the coil section. This influenced the viscosity variability along the coil, especially for the fruit juice, with a pronounced pseudoplastic behaviour (flow behaviour index of 0.5). This viscosity variation was more influenced by the strain rate than the viscosity change with temperature, as the fruit juice showed a moderate energy activation (8.2 kJ/mol).



中文翻译:

粘性流体盘管传热过程的数值模拟

本研究展示了层流状态下牛顿和非牛顿流体在螺旋盘管中的数值模拟结果。作为一项实际贡献,数值模拟使用了非牛顿流体,其流变特性是通过实验测量的。

在两种非牛顿流体中,螺旋截面的传热速率均高于直线截面。对于果汁,在Re g为 255 和 634 的情况下,盘管处的传热系数 ( h w ) 分别达到 1000 和 1350 W/m 2 K,比直段高 73% 和 126% , 分别。对于羧甲基纤维素溶液,这些差异介于 76% ( Re g  = 255) 和 210% ( Re g  = 634) 之间,在 1950 和 2700 W/m 2 K的线圈处达到h w值。

在所有非牛顿情况下,线圈部分的流体混合都得到了改善。这影响了沿线圈的粘度变化,特别是对于果汁,具有明显的假塑性行为(流动行为指数为 0.5)。这种粘度变化受应变速率的影响比粘度随温度变化的影响更大,因为果汁显示出适度的能量活化(8.2 kJ/mol)。

更新日期:2022-06-20
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