Purpose

This paper aims to focuses on by investigate the heat transmission and free convective flow of a suspension of nano encapsulated phase change materials (NEPCMs) within an enclosure. Particles of NEPCM have a core-shell structure, with phase change material (PCM) serving as the core.

Design/methodology/approach

The enclosure consists of a square chamber with an insulated wall on top and bottom and vertical walls that are differently heated. The governing equations are investigated using the finite element technique. A grid inspection and validation test are done to confirm the precision of the results.

Findings

The effects of fusion temperature (varying from 0.1 to 0.9), Stefan number (changing from 0.2 to 0.7), Rayleigh number (varying from 10³ to 10⁶) and volume fraction of NEPCM nanoparticles (changing from 0 to 0.05) on the streamlines, isotherms, heat capacity ratio and average Nusselt number are investigated using graphs and tables. From this investigation, it is found that using a NEPCM nano suspension results in a significant enhancement in heat transfer compared to pure fluid. This augmentation becomes more important for the low Stefan number, which is around 16.57% approximately at 0.2. Secondary recirculation is formed near the upper left corner as a result of non-uniform heating of the left vertical border. This eddy expands notably as the Rayleigh number rises. The study findings indicate that the NEPCM nanosuspension has the potential to act as a smart working fluid, significantly enhancing average Nusselt numbers in enclosed chambers.

Research limitations/implications

The NEPCM particle consists of a core (n-octadecane, a phase-change material) and a shell (PMMA, an encapsulation material). The host fluid water and the NEPCM particles are considered to form a dilute suspension.

Practical implications

Using NEPCMs in energy storage thermal systems show potential for improving heat transfer efficiency in several engineering applications. NEPCMs merge the beneficial characteristics of PCMs with the enhanced thermal conductivity of nanoparticles, providing a flexible alternative for effective thermal energy storage and control.

Originality/value

This paper aims to explore the free convective flow and heat transmission of NEPCM water-type nanofluid in a square chamber with an insulated top boundary, a uniformly heated bottom boundary, a cooled right boundary and a non-uniformly heated left boundary.

中文翻译：

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由 NEPCM 水纳米流体填充的非均匀加热外壳中的传热

 目的

本文旨在通过研究纳米封装相变材料 （NEPCM） 悬浮液在外壳内的热传递和自由对流来研究。NEPCM 的颗粒具有核壳结构，以相变材料 （PCM） 为核心。

设计/方法/方法

外壳由一个方形腔室组成，顶部和底部有绝缘壁，垂直壁具有不同的加热方式。使用有限元技术研究控制方程。进行网格检查和验证测试以确认结果的精度。

 发现

聚变温度 （从 0.1 到 0.9 变化）、Stefan 数 （从 0.2 到 0.7） 、瑞利数 （从 10³ 到 10⁶） 和体积分数 （从 0 到 0.05） 对流线、等温线、热容比和平均努塞尔数的影响使用图表研究了。从这项调查中发现，与纯流体相比，使用 NEPCM 纳米悬浮液可显着增强传热。这种增强对于低 Stefan 数变得更加重要，Stefan 数约为 16.57%，约为 0.2。由于左垂直边界的不均匀加热，在左上角附近形成二次再循环。这个涡流随着瑞利数的上升而显著扩大。研究结果表明，NEPCM 纳米悬浮液有可能充当智能工作流体，显著提高封闭腔室中的平均努塞尔数。

研究局限性/影响

NEPCM 颗粒由一个核心（正十八烷，一种相变材料）和一个壳（PMMA，一种封装材料）组成。主体流体水和 NEPCM 颗粒被认为形成稀悬浮液。

 实际意义

在储能热系统中使用 NEPCM 显示出在多种工程应用中提高传热效率的潜力。NEPCM 将 PCM 的有益特性与纳米颗粒增强的导热性相结合，为有效的热能储存和控制提供了一种灵活的替代方案。

 原创性/价值

本文旨在探讨 NEPCM 水型纳米流体在具有绝缘顶部边界、均匀加热的底部边界、冷却的右边界和非均匀加热的左边界的方室中的自由对流和传热。