基于几个可靠参数识别各种气泡柱中的局部各向同性湍流条件

IF 1.8 Q3 MECHANICS Fluids Pub Date : 2023-12-04 DOI:10.3390/fluids8120314
S. Nedeltchev
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引用次数: 0

摘要

气泡塔在化工行业中有着广泛的应用。在许多工业应用中,这些重要的气液接触器在搅拌湍流状态下工作。原则上,确定每个BC反应器的运行条件是必要的,其中局部各向同性湍流已经建立。研究结果表明,不同参数(Kolmogorov熵、相关维数和新型混合指数)均呈单调递减趋势。这一发现可以用不断增大的合并气泡尺寸来解释,这给气液系统带来了更多的秩序,因此任何熵或混沌参数都应该随着表面气体速度Ug的增加而减小。研究了新参数在不同气液体系中的分布。它们是从不同的压力信号(表压或绝对压)中提取的。在本研究中,使用了不同直径的bc,并配备了不同的气体分布器。结果表明,所研究的参数可以成功地与微涡的长度尺度相关联,从而间接确定了局部各向同性湍流理论在各种工况下的Ug适用范围。分析了整体气含率分布,根据Ug值的指数,发现在所研究的醇类水溶液中,气泡床(BB)的条件是均匀的,而在不同的BCs曝气的空气自来水系统中,BB的条件是不均匀的。这一结果表明,局部各向同性湍流条件主要在相应的测量位置周围占主导地位。
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Identification of Local Isotropic Turbulence Conditions in Various Bubble Columns Based on Several Reliable Parameters
Bubble columns (BCs) are widely used in the chemical industry. In many industrial applications, these important gas-liquid contactors operate in a churn-turbulent flow regime. In principle, it is essential to determine the operating conditions in every BC reactor, in which local isotropic turbulence is established. In this work, it was demonstrated that several different parameters (Kolmogorov entropy, correlation dimension and novel hybrid index) follow a monotonic decreasing trend. This finding could be explained by the constantly increasing coalesced bubble size, which brings more order into the gas-liquid system and thus any entropic or chaotic parameter should decrease with the increase in the superficial gas velocity Ug. The profiles of the new parameters in various gas-liquid systems were studied. They were extracted from different pressure signals (gauge or absolute). In this research, BCs of different diameter and equipped with different gas distributors were used. It was demonstrated that the studied parameters could be successfully correlated with the length scale of the micro eddies and thus the Ug range of applicability of the local isotropic turbulence theory under various operating conditions was indirectly determined. The overall gas holdup profiles were analyzed and, based on the exponent of the Ug value, it was found that in the aqueous solutions of alcohols studied, the conditions in the bubble bed (BB) are homogeneous, whereas in the air-tap water system aerated in different BCs, the conditions in the BB are heterogeneous. This result implies that the local isotropic turbulence conditions predominate mainly around the corresponding measurement positions.
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来源期刊
Fluids
Fluids Engineering-Mechanical Engineering
CiteScore
3.40
自引率
10.50%
发文量
326
审稿时长
12 weeks
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