Numerical modelling of hydrothermal fluid flow and heat transfer in a tubular heat exchanger under near critical conditions
Numerical modelling of hydrothermal fluid flow and heat transfer in a tubular heat exchanger under near critical conditions
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DOI：
10.1016/j.supflu.2011.03.007
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发表时间：
2011-07-01
影响因子：
3.9
通讯作者：
Wang, Xue Z.
中科院分区：
文献类型：
--
作者：
Ma, Cai Y.;Tighe, Christopher J.;Wang, Xue Z.
连续水热流合成方法对于纳米颗粒金属氧化物的制造是令人感兴趣的。在这样的过程中，最初形成的纳米颗粒核（在浆料中）可以在它们通过合成设备时继续生长和附聚以产生更大的颗粒。这些过程可以加宽尺寸分布，并且还影响回收产品中的最终颗粒形状。因此，使用高效热交换器快速冷却或骤冷初始纳米颗粒浆料可以最小化或停止进一步的结晶/团聚过程。这可以通过基于使用计算流体动力学（CFD）建模方法对流型和传热分布的详细检查来优化热交换器的设计来实现。热交换器中预测的流动和传热模式还可以提供详细信息，用于识别任何传热恶化或可能发生进一步反应的热点。采用CFD模拟方法对连续水热合成系统中管式换热器的传热过程进行了数值模拟，考察了不同操作条件（包括热浆进口温度、流量和冷却水进口流量）对换热器内流体和热力特性的影响。模拟结果表明，预测的温度和传热系数与实验测量结果吻合良好。(C)2011 Elsevier B. V.保留所有权利。
Continuous hydrothermal flow synthesis processes are of interest for the manufacture of nanoparticle metal oxides. In such processes, nanoparticle nuclei (in a slurry) which are initially formed, may continue to grow and agglomerate to generate larger particles as they pass through the synthesis apparatus. These processes can widen the size distribution and also affect the ultimate particle shape in the recovered product. Therefore, fast cooling or quenching the initial nanoparticle slurry using a highly efficient heat exchanger may minimise or stop further crystallisation/agglomeration processes. This may be achieved by optimising the design of the heat exchanger based on detailed examination of flow patterns and heat transfer profiles using a computational fluid dynamics (CFD) modelling approach. The predicted flow and heat transfer patterns in the heat exchanger can also provide detailed information for the identification of any heat transfer deterioration or hot spots where further reactions may occur. This paper employs a CFD modelling approach to simulate the heat transfer processes in a tubular heat exchanger of a continuous hydrothermal flow synthesis system and also to examine the effect of various operating conditions, including inlet temperature and flowrate of hot slurry and inlet flowrate of cooling water, on the fluid and thermal features in the heat exchanger. The simulated results show that the predicted temperature and heat transfer coefficient are in good agreement with experimental measurements. (C) 2011 Elsevier B.V. All rights reserved.