Abstract
The present study investigates the natural convection in a wavy enclosure caused by a thermal difference between a cold wall and a hot undulated wall. The enclosure is filled with hybrid nanofluids. The hybrid nanofluids are formed of a phase change material (PCM) suspended in the water. The PCM utilizes polyurethane as the shell and nonadecane as the core. The core absorbs or releases its energy in the shape of latent heat inside the water and contributes to thermal energy storage and heat transfer. The governing equations are expressed in PDEs and solved by the finite element method (FEM). Parametric studies were used to analyze the solid concentration, fusion temperature, amplitude of corrugation, number of corrugations, and Rayleigh number. It is found that the heat transfer rate enhances by the rise of the latent heat of the NEPCM cores. The global heat transfer can be improved by more than 12 % by adding 1 % of NEPCM particles volume fraction. However, the heat transfer tends to decrease by applying the wavy surface.
Highlights
Nanotechnology deals with extremely small things that enable us to modify individual atoms
It is noted that the heat capacity of the core is the mean of the heat capacities of the fluid and solid states. is is due to the nanoparticles core subject to solid and fluid phase; the latent heat was engaged in the heat capacity of the nanoencapsulated phase change materials (NEPCMs). is heat can be formulated by performing rectangular, triangular, or sinusoidal functions as follows [46]: Cp,p
Parametric studies were used to analyze the related nondimensional quantity: the amplitude of undulated surface, 0 ≤ A ≤ 0.3, the number of undulated surface, 3 ≤ N ≤ 6, the fusion temperatures, 0.1 ≤ θf ≤ 0.5, the Rayleigh number, 100 ≤ Ra ≤ 106, and nanoparticles concentration, 0.0 ≤ φ ≤ 0.05. e core weight of the nanoparticles is below water, and their shell weight is above water, so that the density ratio is below unity. e thermal expansion coefficient water is greatly above these particles. e dilute solution of NEPCMs has Nc 23.8 and Nv 12.5 [44]. e sensible capacity ratio of the NEPCM is 0.32
Summary
Nanotechnology deals with extremely small things that enable us to modify individual atoms. Convection heat transfer in enclosures filled with nanofluids having wavy wall was studied by Abu-Nada and Oztop [11]. Esmaeilpour and Abdollahzadeh [12] studied natural convection and entropy generation of copper-water inside an enclosure having different types of vertical wavy walls. Solidification of nanoenhanced phase change material (PCM) in a wavy enclosure was considered by Kashani et al [27]. Abdollahzadeh and Esmaeilpour [31] proposed phase change material having nanofluids and corrugate surface. Selimefendigil et al [35] studied the conjugate heat transfer characteristic of nanofluid in a square enclosure, where a PCM is attached on the vertical wall. E present study aims to study the natural convection in a wavy enclosure filled with water containing nanoencapsulated phase change material. The corrugated absorber improves the exergetic performance and the NEPCMs increase the thermal performance
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