Abstract

In the present work, 3-D numerical simulations have been carried out to understand the flow patterns and heat transfer on the jacket side of a stirred vessel under mixed convection conditions. Various parameters have been varied (1 ≤ U_in ≤ 20 m/s, 30 ≤ ΔT ≤ 60 K, 30 ≤ J_g ≤ 150 mm, D_i= 1 and 3 m) to understand their effect on the heat transfer and pressure drop on the jacket side. SST k-ω model has been used for the numerical simulations because of its capability to predict natural convection heat transfer and low Re forced convection heat transfer. It was found that, the heat transfer coefficient increases by 40-80% by increasing the inlet fluid velocity from 1 to 5 m/s. The pressure drop increases by 120-200% and heat transfer per unit pumping power decreases by 60-75% as we increase the velocity from 1 to 5 m/s. It has also been observed that the flow inside the jacket is 3-D, nonuniform and has dead zones and hot pockets at various locations. The effects of inlet flow impinging have also been studied by varying inlet diameter and removing inlet pipe. Impinging by inlet flow on jacket wall contributes about 10-20% to heat transfer and 10-25% to pressure drop. Due to the presence of recirculating flow zones, dead zones, and impinging effect, existing correlations are not suitable for the estimations of heat transfer in large jackets. Large differences have been observed between the 3-D CFD predictions and the widely used empirical correlations. Further, the 3-D CFD predictions have been shown to be comparable to the experimental data available in the published literature. Based on simulations performed in the present work and also validated by experimental data, a new correlation has been proposed which is expected to be useful to design engineers, particularly for those, having limited computational facility.

摘要

在本工作中，已经进行了3-D数值模拟，以了解在混合对流条件下搅拌容器的夹套侧的流动方式和传热。各种参数已经被改变（1≤  û_在≤为20m / s，30≤ΔT≤60 K，30≤  Ĵ_克≤150毫米d_我= 1和3米）来了解它们对热传递和压降的效果在夹克的一面。SSTk-ω模型已被用于数值模拟，因为它具有预测自然对流传热和低Re的能力。强制对流换热。已发现，通过将入口流体速度从1 m / s增加到5 m / s，传热系数增加40-80％。当速度从1 m / s增加到5 m / s时，压降增加120-200％，每单位泵浦功率的热传递减少60-75％。还已经观察到，外套内部的流动是3-D的，不均匀的，并且在各个位置具有死区和热袋。还通过改变进气口直径并拆下进气管来研究进气流撞击的影响。入口流对夹套壁的撞击对传热的贡献约为10-20％，对压降的贡献约为10-25％。由于存在循环流动区，死区和撞击效应，因此现有的相关性不适用于大型夹套中的传热估算。在3-D CFD预测与广泛使用的经验相关性之间已经观察到很大的差异。此外，已显示3-D CFD预测与已出版文献中可用的实验数据相当。基于当前工作中进行的模拟并通过实验数据进行了验证，提出了一种新的相关性，它有望对设计工程师特别是计算能力有限的设计工程师有用。