Purpose

The present numerical investigation examines the magnetohydrodynamic (MHD) double diffusion natural convection of power-law non-Newtonian nano-encapsulated phase change materials (NEPCMs) in a trapezoidal cavity.

Design/methodology/approach

The governing Navier-Stokes, energy and concentration equations based on the Cartesian curvilinear coordinates are solved using the collocated grid arrangement’s finite volume method. The in-house FORTRAN code is validated with the different benchmark problems. The NEPCM nanoparticles consist of a core-shell structure with Phase Change Material (PCM) at the core. The enclosure, shaped as a trapezoidal hollow, features a warmed (T_h) left wall and a cold (T_c) right wall. Various parameters are considered, including the power law index (0.6 ≤ n ≤ 1.4), Hartmann number (0 ≤ Ha ≤ 30), Rayleigh number (10⁴ ≤ Ra ≤ 10⁵) and fixed variables such as buoyancy ratio (Br = 0.8), Prandtl number (Pr = 6.2), Lewis number (Le = 5), fusion temperature (Θ_f = 0.5) and volume fraction (ϕ = 0.04).

Findings

The findings indicate a decrease in local Nusselt (Nu) and Sherwood (Sh) numbers with increasing Hartmann numbers (Ha). Additionally, for a shear-thinning fluid (n = 0.6) results in the maximum local Nu and Sh values. As the Rayleigh number (Ra) increases from 10⁴ to 10⁵, the structured vortex in the streamline pattern is disturbed. Furthermore, for different Ra values, an increase in n from 0.6 to 1.4 leads to a 67.43% to 76.88% decrease in average Nu and a 70% to 77% decrease in average Sh.

Research limitations/implications

This research is for two-dimensioal laminar flow only.

Practical implications

PCMs represent a class of practical substances that behave as a function of temperature and have the innate ability to absorb, release and store heated energy in the form of hidden fusion enthalpy, or heat. They are valuable in these systems as they can store significant energy at a relatively constant temperature through their latent heat phase change.

Originality/value

As per the literature review and the authors’ understanding, an examination has never been conducted on MHD double diffusion natural convection of power-law non-Newtonian NEPCMs within a trapezoidal enclosure. The current work is innovative since it combines NEPCMs with the effect of magnetic field Double diffusion Natural Convection of power-law non-Newtonian NEPCMs in a Trapezoidal enclosure. This outcome can be used to improve thermal management in energy storage systems, increasing safety and effectiveness.

中文翻译：

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梯形外壳内幂律非牛顿纳米封装相变材料的磁流体动力学双扩散自然对流

 目的

目前的数值研究研究了梯形腔中幂律非牛顿纳米封装相变材料（NEPCM）的磁流体动力学（MHD）双扩散自然对流。

设计/方法论/途径

使用并置网格布置的有限体积法求解基于笛卡尔曲线坐标的纳维-斯托克斯控制方程、能量方程和浓度方程。内部 FORTRAN 代码通过不同的基准问题进行了验证。 NEPCM 纳米粒子由核壳结构组成，核心为相变材料（PCM）。外壳形状为梯形空心，具有暖 ( T _h ) 左壁和冷 ( T _c ) 右壁。考虑了各种参数，包括幂律指数（0.6 ≤ n ≤ 1.4）、哈特曼数（0 ≤ Ha ≤ 30）、瑞利数（10 ⁴ ≤ Ra ≤ 10 ⁵ ）和固定变量，如浮力比（ Br = 0.8） ）、普朗特数（ Pr = 6.2）、路易斯数（ Le = 5）、熔化温度（θ _f = 0.5）和体积分数（Φ = 0.04）。

 发现

研究结果表明，随着哈特曼数 ( Ha ) 的增加，当地努塞尔 ( Nu ) 和舍伍德 ( Sh ) 数减少。此外，对于剪切稀化流体 ( n = 0.6) 会产生最大局部Nu和Sh值。随着瑞利数（ Ra ）从10 ⁴增加到10 ⁵ ，流线图案中的结构涡被扰乱。此外，对于不同的Ra值， n从0.6增加到1.4导致平均Nu减少67.43%到76.88%，平均Sh减少70%到77%。

研究局限性/影响

本研究仅针对二维层流。

 实际意义

相变材料代表一类实用物质，其行为随温度变化，并且具有以隐藏的聚变热函或热量的形式吸收、释放和存储热能的固有能力。它们在这些系统中很有价值，因为它们可以通过潜热相变在相对恒定的温度下存储大量能量。

 原创性/价值

根据文献综述和作者的理解，从未对梯形外壳内幂律非牛顿 NEPCM 的 MHD 双扩散自然对流进行过研究。当前的工作具有创新性，因为它将 NEPCM 与梯形外壳中幂律非牛顿 NEPCM 的磁场双扩散自然对流效应结合起来。这一结果可用于改善储能系统的热管理，提高安全性和有效性。