崖体上纳米流体在稳定和非稳定流动下的传热和熵生成特性：两相方法

IF 6.4 2区工程技术 Q1 THERMODYNAMICS

Case Studies in Thermal Engineering Pub Date : 2024-10-03 DOI:10.1016/j.csite.2024.105242

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引用次数: 0

摘要

由于具有较高的热导率，纳米流体有可能成为从内部流到外部流等各种应用的冷却剂。为了获得准确的结果，采用了一个两相模型来模拟纳米粒子与基液之间的相互作用。在各种体积分数（0.5%-2%）的稳定（20 < Re < 100）和非稳定（Re = 150 和 300）流动条件下，纳米流体（Al2O3 和水）在圆形和方形圆柱体等崖体上流动时的传热和熵生成特性已经得到验证。在定量和定性方面，同样使用了平均努塞尔特数、表面努塞尔特数、传热增强比和熵生成等参数。在稳定流和非稳定流中，传热率随着流速和体积分数的增加而增加。稳定流的传热增强率在 1.10 到 1.35 之间。对于非稳定流（Re = 150 & Re = 300），纳米流体的传热增强比高于水，范围在 1.10-1.8 之间。这归因于流体的早期分离和大量再循环区域的存在。随着 Re 值的增加，圆形和方形圆柱体的熵产生量减少。与纳米流体相比，水的熵产生量更高。

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Heat transfer and entropy generation characteristics of nanofluid flow over bluff bodies under steady and unsteady flow: A two-phase approach

Owing to higher thermal conductivity, nanofluids have the potential to be the coolant for various applications ranging from internal to external flows. A two-phase model is implemented to model the interaction between nanoparticles and base fluid to obtain accurate results. Heat transfer and entropy generation characteristics of nanofluid (Al₂O₃ and water) flow over bluff bodies such as circular and square cylinders for steady (20 < Re < 100) and unsteady (Re = 150 and 300) flow conditions have been carried out for various volume fractions (0.5–2 %). The same has been expressed in quantitative and qualitative aspects with parameters such as mean Nusselt number, surface Nusselt number, heat transfer enhancement ratio, and entropy generation. Heat transfer rate increases with an increase in flow rate and volume fraction for both steady and unsteady flow. Heat transfer enhancement in steady flow ranges from 1.10 to 1.35. For unsteady flow (Re = 150 & Re = 300), nanofluid's heat transfer enhancement ratio is higher than water in the range of 1.10–1.8. This is attributed to the early separation of flow and the presence of large recirculatory regions. With the increase in Re, the entropy generation decreases for circular and square cylinders. Compared to nanofluid, the entropy generation is higher for water.

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来源期刊

Case Studies in Thermal Engineering Chemical Engineering-Fluid Flow and Transfer Processes

CiteScore

8.60

自引率

11.80%

发文量

812

审稿时长

76 days

期刊介绍： Case Studies in Thermal Engineering provides a forum for the rapid publication of short, structured Case Studies in Thermal Engineering and related Short Communications. It provides an essential compendium of case studies for researchers and practitioners in the field of thermal engineering and others who are interested in aspects of thermal engineering cases that could affect other engineering processes. The journal not only publishes new and novel case studies, but also provides a forum for the publication of high quality descriptions of classic thermal engineering problems. The scope of the journal includes case studies of thermal engineering problems in components, devices and systems using existing experimental and numerical techniques in the areas of mechanical, aerospace, chemical, medical, thermal management for electronics, heat exchangers, regeneration, solar thermal energy, thermal storage, building energy conservation, and power generation. Case studies of thermal problems in other areas will also be considered.