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A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Synthesis, Interfaces and Nanostructures".

Deadline for manuscript submissions: closed (30 September 2022) | Viewed by 24916

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Prof. Dr. S M Sohel Murshed

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University of Lisbon (IST), Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal
Interests: nanofluids; thermophysical properties of fluids; advanced cooling technologies; droplet-based microfluidics; energy technologies; fluids flow and phase-change heat transfer; thermal managements
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Dear Colleagues,

Nanofluids have recently emerged as a hot research field, as evidenced by the worldwide research and publication explosion on them. Despite being a popular topic, though, the real progress of this field is rather slow, and its real-world application is impeded due to various complicated challenges, including its anomalous thermophysical properties, stability, sustainable usefulness, and compatibility in many conventional systems or devices. Although extensive research efforts have been focused on thermophysical properties of nanofluids and most of the research has demonstrated significant enhancement in thermophysical properties, there remains a large volume of scattered and inconsistent data leading to not yet reaching unanimous conclusions on the enhancement and its underlying mechanisms. Additionally, a large number of research efforts have been made to develop models for the prediction of the thermophysical properties, particularly thermal conductivity of nanofluids. Again, no widely accepted theoretical models are available for nanofluids. The viscosity of nanofluids is also a key property, particularly important for their applications under a flowing condition. On top of all these, a major challenge with nanofluids is to obtain sustainable stability and persistent properties over a long duration. All these issues are very crucial for nanofluid development and applications, and research in these areas has been growing in recent years.

The aim of this Special Issue is to publish a wide range of topics related to nanofluids with special emphasis on thermophysical and heat transfer properties and features, challenges, and applications in all spectra in order make this Special Issue a useful resource for the people involved in this field as well as for the progress of this field.

Articles to be considered for this Special Issue include original full papers, communications, and critical reviews in any area/topic of the keywords and beyond.

Prof. Dr. S M Sohel Murshed
Guest Editor

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Keywords

Nanofluids
Hybrid nanofluids
Ionanofluids
Nanosalts
NanoPCM
Nanoparticles
Thermophysical properties
Convective heat transfer performance
Boiling heat transfer features
Nanofluids in MEMs
Nanofluid applications

Published Papers (13 papers)

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Editorial

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Open AccessEditorial

Heat Transfer and Fluids Properties of Nanofluids

S M Sohel Murshed

Nanomaterials 2023, 13(7), 1182; https://doi.org/10.3390/nano13071182 - 27 Mar 2023

Cited by 1 | Viewed by 896

Abstract

As it is popular research field, extensive research has been performed in various areas of nanofluids, and most of the studies have demonstrated significant enhancements in their thermophysical properties and thermal transport performance compared to those of conventional thermal fluids. However, there have been unanimous conclusions regarding such enhancements and their underlying mechanisms. Nanofluids’ potential and thermal applications mainly depend on their convective and boiling heat transfer performances, which are also not unbiased in the literature. On top of this, a major challenge with nanofluids is obtaining sustainable stability and persistent properties over a long duration. All these issues are very crucial for nanofluids’ development and applications, and a lot of research in these areas has been conducted in recent years. Thus, this Special Issue, featuring a dozen of high-quality research and reviews on different types of nanofluids and their important topics related to thermophysical and electrical properties as well as convective and boiling heat transfer characteristics, is of great significance for the progress and real-world applications of this new class of fluids. Full article

(This article belongs to the Special Issue Heat Transfer and Fluids Properties of Nanofluids)

Research

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Open AccessArticle

Comparisons of Numerical and Experimental Investigations of the Thermal Performance of Al₂O₃ and TiO₂ Nanofluids in a Compact Plate Heat Exchanger

Wagd Ajeeb

and

S M Sohel Murshed

Nanomaterials 2022, 12(20), 3634; https://doi.org/10.3390/nano12203634 - 17 Oct 2022

Cited by 4 | Viewed by 758

Abstract

This study reports the thermal performance of Al₂O₃ and TiO₂ nanofluids (NFs) flowing inside a compact plate heat exchanger (CPHE) by comparing the experimental and numerical investigations. The NF samples were prepared for five concentrations each of Al₂O₃ and TiO₂ nanoparticles dispersed in distilled water (DW) as a base fluid (BF). The stability of NF samples was ensured, and their viscosity and thermal conductivity were measured. Firstly, the experimental measurements were performed for the heat transfer and fluid flow of the NFs in the plate heat exchanger (PHE) system and then the numerical investigation method was developed for the same PHE dimensions and operation conditions of the experimental investigation. A finite volume method (FVM) and single-phase fluid were used for numerical modelling. The obtained experimental and numerical results show that the thermal performance of the CPHE enhances by adding nanoparticles to the BFs. Furthermore, numerical predictions present lower values of convection heat transfer coefficients than the experimental measurements with a maximum deviation of 12% at the highest flow rate. Nevertheless, the numerical model is suitable with acceptable accuracy for the prediction of NFs through PHE and it becomes better for relatively small particles’ concentrations and low flow rates. Full article

(This article belongs to the Special Issue Heat Transfer and Fluids Properties of Nanofluids)

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Open AccessArticle

Natural Convection within Inversed T-Shaped Enclosure Filled by Nano-Enhanced Phase Change Material: Numerical Investigation

and

Nanomaterials 2022, 12(17), 2917; https://doi.org/10.3390/nano12172917 - 24 Aug 2022

Cited by 19 | Viewed by 1191

Abstract

Energy saving has always been a topic of great interest. The usage of nano-enhanced phase change material NePCM is one of the energy-saving methods that has gained increasing interest. In the current report, we intend to simulate the natural convection flow of NePCM inside an inverse T-shaped enclosure. The complex nature of the flow results from the following factors: the enclosure contains a hot trapezoidal fin on the bottom wall, the enclosure is saturated with pours media, and it is exposed to a magnetic field. The governing equations of the studied system are numerically addressed by the higher order Galerkin finite element method (GFEM). The impacts of the Darcy number (Da = 10⁻²–10⁻⁵), Rayleigh number (Ra = 10³–10⁶), nanoparticle volume fraction (φ = 0–0.08), and Hartmann number (Ha = 0–100) are analyzed. The results indicate that both local and average Nusselt numbers were considerably affected by Ra and Da values, while the influence of other parameters was negligible. Increasing Ra (increasing buoyancy force) from 10³ to 10⁶ enhanced the maximum average Nusselt number by 740%, while increasing Da (increasing the permeability) from 10⁻⁵ to 10⁻² enhanced both the maximum average Nusselt number and the maximum local Nusselt number by the same rate (360%). Full article

(This article belongs to the Special Issue Heat Transfer and Fluids Properties of Nanofluids)

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Open AccessArticle

Effect of Nanoparticle Size and Concentration on Pool Boiling Heat Transfer with TiO₂ Nanofluids on Laser-Textured Copper Surfaces

and

Nanomaterials 2022, 12(15), 2611; https://doi.org/10.3390/nano12152611 - 29 Jul 2022

Cited by 5 | Viewed by 1100

Abstract

The enhancement of boiling heat transfer has been extensively shown to be achievable through surface texturing or fluid property modification, yet few studies have investigated the possibility of coupling both enhancement approaches. The present work focuses on exploring the possibility of concomitant enhancement of pool boiling heat transfer by using TiO₂-water nanofluid in combination with laser-textured copper surfaces. Two mass concentrations of 0.001 wt.% and 0.1 wt.% are used, along with two nanoparticle sizes of 4–8 nm and 490 nm. Nanofluids are prepared using sonification and degassed distilled water, while the boiling experiments are performed at atmospheric pressure. The results demonstrate that the heat transfer coefficient (HTC) using nanofluids is deteriorated compared to using pure water on the reference and laser-textured surface. However, the critical heat flux (CHF) is significantly improved at 0.1 wt.% nanoparticle concentration. The buildup of a highly wettable TiO₂ layer on the surface is identified as the main reason for the observed performance. Multiple subsequent boiling experiments using nanofluids on the same surface exhibited a notable shift in boiling curves and their instability at higher concentrations, which is attributable to growth of the nanoparticle layer on the surface. Overall, the combination of nanofluids boiling on a laser-textured surface proved to enhance the CHF after prolonged exposure to highly concentrated nanofluid, while the HTC was universally and significantly decreased in all cases. Full article

(This article belongs to the Special Issue Heat Transfer and Fluids Properties of Nanofluids)

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Open AccessArticle

Thermal and Hydraulic Performances of Carbon and Metallic Oxides-Based Nanomaterials

Haitham Abdulmohsin Afan

Mohammed Suleman Aldlemy

Adnan Hashim Abdulkadhim

Miklas Scholz

and

Zaher Mundher Yaseen

Nanomaterials 2022, 12(9), 1545; https://doi.org/10.3390/nano12091545 - 03 May 2022

Cited by 1 | Viewed by 1409

Abstract

For companies, notably in the realms of energy and power supply, the essential requirement for highly efficient thermal transport solutions has become a serious concern. Current research highlighted the use of metallic oxides and carbon-based nanofluids as heat transfer fluids. This work examined two carbon forms (PEG@GNPs & PEG@TGr) and two types of metallic oxides (Al₂O₃ & SiO₂) in a square heated pipe in the mass fraction of 0.1 wt.%. Laboratory conditions were as follows: 6401 ≤ Re ≤ 11,907 and wall heat flux = 11,205 W/m². The effective thermal–physical and heat transfer properties were assessed for fully developed turbulent fluid flow at 20–60 °C. The thermal and hydraulic performances of nanofluids were rated in terms of pumping power, performance index (PI), and performance evaluation criteria (PEC). The heat transfer coefficients of the nanofluids improved the most: PEG@GNPs = 44.4%, PEG@TGr = 41.2%, Al₂O₃ = 22.5%, and SiO₂ = 24%. Meanwhile, the highest augmentation in the Nu of the nanofluids was as follows: PEG@GNPs = 35%, PEG@TGr = 30.1%, Al₂O₃ = 20.6%, and SiO₂ = 21.9%. The pressure loss and friction factor increased the highest, by 20.8–23.7% and 3.57–3.85%, respectively. In the end, the general performance of nanofluids has shown that they would be a good alternative to the traditional working fluids in heat transfer requests. Full article

(This article belongs to the Special Issue Heat Transfer and Fluids Properties of Nanofluids)

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Open AccessArticle

Molecular Dynamics Simulation on Behaviors of Water Nanodroplets Impinging on Moving Surfaces

Hao Zhang

Ling Pan

and

Xuqing Xie

Nanomaterials 2022, 12(2), 247; https://doi.org/10.3390/nano12020247 - 13 Jan 2022

Cited by 3 | Viewed by 1441

Abstract

Droplets impinging on solid surfaces is a common phenomenon. However, the motion of surfaces remarkably influences the dynamical behaviors of droplets, and related research is scarce. Dynamical behaviors of water nanodroplets impinging on translation and vibrating solid copper surfaces were investigated via molecular dynamics (MD) simulation. The dynamical characteristics of water nanodroplets with various Weber numbers were studied at five translation velocities, four vibration amplitudes, and five vibration periods of the surface. The results show that when water nanodroplets impinge on translation surfaces, water molecules not only move along the surfaces but also rotate around the centroid of the water nanodroplet at the relative sliding stage. Water nanodroplets spread twice in the direction perpendicular to the relative sliding under a higher surface translation velocity. Additionally, a formula for water nanodroplets velocity in the translation direction was developed. Water nanodroplets with a larger Weber number experience a heavier friction force. For cases wherein water nanodroplets impinge on vibration surfaces, the increase in amplitudes impedes the spread of water nanodroplets, while the vibration periods promote it. Moreover, the short-period vibration makes water nanodroplets bounce off the surface. Full article

(This article belongs to the Special Issue Heat Transfer and Fluids Properties of Nanofluids)

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Open AccessArticle

Enhanced Heat Transfer for NePCM-Melting-Based Thermal Energy of Finned Heat Pipe

and

Nanomaterials 2022, 12(1), 129; https://doi.org/10.3390/nano12010129 - 31 Dec 2021

Cited by 24 | Viewed by 1616

Abstract

Using phase change materials (PCMs) in energy storage systems provides various advantages such as energy storage at a nearly constant temperature and higher energy density. In this study, we aimed to conduct a numerical simulation for augmenting a PCM’s melting performance within multiple tubes, including branched fins. The suspension contained Al₂O₃/n-octadecane paraffin, and four cases were considered based on a number of heated fins. A numerical algorithm based on the finite element method (FEM) was applied to solve the dimensionless governing system. The average liquid fraction was computed over the considered flow area. The key parameters are the time parameter (

100 \leq t \leq 600 s)

and the nanoparticles’ volume fraction (

0 % \leq φ \leq 8 %)

. The major outcomes revealed that the flow structures, the irreversibility of the system, and the melting process can be controlled by increasing/decreasing number of the heated fins. Additionally, case four, in which eight heated fins were considered, produced the largest average liquid fraction values. Full article

(This article belongs to the Special Issue Heat Transfer and Fluids Properties of Nanofluids)

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Open AccessArticle

Modelling Thermal Conduction in Polydispersed and Sintered Nanoparticle Aggregates

Nikolaos P. Karagiannakis

Eugene D. Skouras

and

Vasilis N. Burganos

Nanomaterials 2022, 12(1), 25; https://doi.org/10.3390/nano12010025 - 22 Dec 2021

Cited by 5 | Viewed by 1779

Abstract

Nanoparticle aggregation has been found to be crucial for the thermal properties of nanofluids and their performance as heating or cooling agents. Most relevant studies in the literature consider particles of uniform size with point contact only. A number of forces and mechanisms are expected to lead to deviation from this ideal description. In fact, size uniformity is difficult to achieve in practice; also, overlapping of particles within aggregates may occur. In the present study, the effects of polydispersity and sintering on the effective thermal conductivity of particle aggregates are investigated. A simulation method has been developed that is capable of producing aggregates made up of polydispersed particles with tailored morphological properties. Modelling of the sintering process is implemented in a fashion that is dictated by mass conservation and the desired degree of overlapping. A noticeable decrease in the thermal conductivity is observed for elevated polydispersity levels compared to that of aggregates of monodisperse particles with the same morphological properties. Sintered nanoaggregates offer wider conduction paths through the coalescence of neighbouring particles. It was found that there exists a certain sintering degree of monomers that offers the largest improvement in heat performance. Full article

(This article belongs to the Special Issue Heat Transfer and Fluids Properties of Nanofluids)

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Open AccessArticle

Appearance of a Solitary Wave Particle Concentration in Nanofluids under a Light Field

Abram I. Livashvili

Victor V. Krishtop

Polina V. Vinogradova

Yuriy M. Karpets

Vyacheslav G. Efremenko

Alexander V. Syuy

Evgenii N. Kuzmichev

and

Pavel V. Igumnov

Nanomaterials 2021, 11(5), 1291; https://doi.org/10.3390/nano11051291 - 14 May 2021

Cited by 3 | Viewed by 1424

Abstract

In this study, the nonlinear dynamics of nanoparticle concentration in a colloidal suspension (nanofluid) were theoretically studied under the action of a light field with constant intensity by considering concentration convection. The heat and nanoparticle transfer processes that occur in this case are associated with the phenomenon of thermal diffusion, which is considered to be positive in our work. Two exact analytical solutions of a nonlinear Burgers-Huxley-type equation were derived and investigated, one of which was presented in the form of a solitary concentration wave. These solutions were derived considering the dependence of the coefficients of thermal conductivity, viscosity, and absorption of radiation on the nanoparticle concentration in the nanofluid. Furthermore, an expression was obtained for the solitary wave velocity, which depends on the absorption coefficient and intensity of the light wave. Numerical estimates of the concentration wave velocity for a specific nanofluid—water/silver—are given. The results of this study can be useful in the creation of next-generation solar collectors. Full article

(This article belongs to the Special Issue Heat Transfer and Fluids Properties of Nanofluids)

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Open AccessEditor’s ChoiceArticle

Numerical Study of Natural Convection Heat Transfer in a Porous Annulus Filled with a Cu-Nanofluid

Lingyun Zhang

Yupeng Hu

and

Minghai Li

Nanomaterials 2021, 11(4), 990; https://doi.org/10.3390/nano11040990 - 12 Apr 2021

Cited by 11 | Viewed by 1972

Abstract

Natural convection heat transfer in a porous annulus filled with a Cu nanofluid has been investigated numerically. The Darcy–Brinkman and the energy transport equations are employed to describe the nanofluid motion and the heat transfer in the porous medium. Numerical results including the isotherms, streamlines, and heat transfer rate are obtained under the following parameters: Brownian motion, Rayleigh number (10³–10⁵), Darcy number (10⁻⁴–10⁻²), nanoparticle volume fraction (0.01–0.09), nanoparticle diameter (10–90 nm), porosity (0.1–0.9), and radius ratio (1.1–10). Results show that Brownian motion should be considered. The nanoparticle volume fraction has a positive effect on the heat transfer rate, especially with high Rayleigh number and Darcy number, while the nanoparticle diameter has an inverse influence. The heat transfer rate is enhanced with the increase of porosity. The radius ratio has a significant influence on the isotherms, streamlines, and heat transfer rate, and the rate is greatly enhanced with the increase of radius ratio. Full article

(This article belongs to the Special Issue Heat Transfer and Fluids Properties of Nanofluids)

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Open AccessArticle

Experimental Investigation on Stability, Viscosity, and Electrical Conductivity of Water-Based Hybrid Nanofluid of MWCNT-Fe₂O₃

and

Nanomaterials 2021, 11(1), 136; https://doi.org/10.3390/nano11010136 - 08 Jan 2021

Cited by 57 | Viewed by 2575

Abstract

The superiority of nanofluid over conventional working fluid has been well researched and proven. Newest on the horizon is the hybrid nanofluid currently being examined due to its improved thermal properties. This paper examined the viscosity and electrical conductivity of deionized water (DIW)-based multiwalled carbon nanotube (MWCNT)-Fe₂O₃ (20:80) nanofluids at temperatures and volume concentrations ranging from 15 °C to 55 °C and 0.1–1.5%, respectively. The morphology of the suspended hybrid nanofluids was characterized using a transmission electron microscope, and the stability was monitored using visual inspection, UV–visible, and viscosity-checking techniques. With the aid of a viscometer and electrical conductivity meter, the viscosity and electrical conductivity of the hybrid nanofluids were determined, respectively. The MWCNT-Fe₂O₃/DIW nanofluids were found to be stable and well suspended. Both the electrical conductivity and viscosity of the hybrid nanofluids were augmented with respect to increasing volume concentration. In contrast, the temperature rise was noticed to diminish the viscosity of the nanofluids, but it enhanced electrical conductivity. Maximum increments of 35.7% and 1676.4% were obtained for the viscosity and electrical conductivity of the hybrid nanofluids, respectively, when compared with the base fluid. The obtained results were observed to agree with previous studies in the literature. After fitting the obtained experimental data, high accuracy was achieved with the formulated correlations for estimating the electrical conductivity and viscosity. The examined hybrid nanofluid was noticed to possess a lesser viscosity in comparison with the mono-particle nanofluid of Fe₂O₃/water, which was good for engineering applications as the pumping power would be reduced. Full article

(This article belongs to the Special Issue Heat Transfer and Fluids Properties of Nanofluids)

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Review

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Open AccessReview

The Pool-Boiling-Induced Deposition of Nanoparticles as the Transient Game Changer—A Review

José Pereira

Ana Moita

and

António Moreira

Nanomaterials 2022, 12(23), 4270; https://doi.org/10.3390/nano12234270 - 01 Dec 2022

Cited by 2 | Viewed by 965

Abstract

It is widely known by the scientific community that the suspended nanoparticles of nanofluids can enhance the thermophysical properties of base fluids and maximize pool-boiling heat transfer. However, the nanoparticles may undergo extended boiling times and deposit onto the heating surfaces under pool-boiling conditions, thus altering their intrinsic characteristics such as wettability and roughness over time. The present study reviews the fundamental mechanisms and characteristics of nanoparticle deposition, and its impact on surface roughness and wettability, density of vaporized core points, and thermal resistance, among other factors. Moreover, the effect of the nanoparticle layer in long-term thermal boiling performance parameters such as the heat transfer coefficient and critical heat flux is also discussed. This work attempts to highlight, in a comprehensive manner, the pros and cons of nanoparticle deposition after extended pool-boiling periods, leading the scientific community toward further investigation studies of pool-boiling heat-transfer enhancement using nanofluids. This review also attempts to clarify the inconsistent results of studies on heat transfer parameters using nanofluids. Full article

(This article belongs to the Special Issue Heat Transfer and Fluids Properties of Nanofluids)

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Open AccessReview

Carbon-Based Nanofluids and Their Advances towards Heat Transfer Applications—A Review

and

Nanomaterials 2021, 11(6), 1628; https://doi.org/10.3390/nano11061628 - 21 Jun 2021

Cited by 48 | Viewed by 6197

Abstract

Nanofluids have opened the doors towards the enhancement of many of today’s existing thermal applications performance. This is because these advanced working fluids exhibit exceptional thermophysical properties, and thus making them excellent candidates for replacing conventional working fluids. On the other hand, nanomaterials of carbon-base were proven throughout the literature to have the highest thermal conductivity among all other types of nanoscaled materials. Therefore, when these materials are homogeneously dispersed in a base fluid, the resulting suspension will theoretically attain orders of magnitude higher effective thermal conductivity than its counterpart. Despite this fact, there are still some challenges that are associated with these types of fluids. The main obstacle is the dispersion stability of the nanomaterials, which can lead the attractive properties of the nanofluid to degrade with time, up to the point where they lose their effectiveness. For such reason, this work has been devoted towards providing a systematic review on nanofluids of carbon-base, precisely; carbon nanotubes, graphene, and nanodiamonds, and their employment in thermal systems commonly used in the energy sectors. Firstly, this work reviews the synthesis approaches of the carbon-based feedstock. Then, it explains the different nanofluids fabrication methods. The dispersion stability is also discussed in terms of measuring techniques, enhancement methods, and its effect on the suspension thermophysical properties. The study summarizes the development in the correlations used to predict the thermophysical properties of the dispersion. Furthermore, it assesses the influence of these advanced working fluids on parabolic trough solar collectors, nuclear reactor systems, and air conditioning and refrigeration systems. Lastly, the current gap in scientific knowledge is provided to set up future research directions. Full article

(This article belongs to the Special Issue Heat Transfer and Fluids Properties of Nanofluids)

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