Enhancing Heat Transfer by Using Nanofluid to Improve the Efficiency of Thermal Systems

Editors

Mohsen Sharifpur

University of Pretoria

Solomon Giwa

Olabisi Onabanjo University

Brusly Solomon A

Karunya Institute of Technology and Sciences

Josua Petrus Meyer

University of Pretoria

Impact

(A) A wavy channel with a magnetic field (Heidary et al., 2017), (B) a triangular corrugated channel and arrangements of magnetic field gradients (Aminfar et al., 2014), (C) a wavy channel with a gradient magnetic field (Mousavi et al., 2020), (D) schematic diagram of a heat exchanger with corrugated plates (Zheng et al., 2020b), and (E) schematic diagram of six arrangements of magnets (Zheng et al., 2020b).

Review

07 April 2022

Review on Thermal Performance of Nanofluids With and Without Magnetic Fields in Heat Exchange Devices

Jiawang Yang

, 3 more and

Bengt Sundén

Addition of nanoparticles into a fluid can improve the heat transfer performance of the base fluid in heat exchangers. In this work, the preparation method and process of nanofluids are introduced, and thermal properties of nanofluids, such as thermal conductivity and viscosity, are discussed deeply. This paper summarizes various theoretical models of thermal conductivity and viscosity of nanofluids. A comprehensive literature survey on applications and limitations of nanofluids has been compiled. This paper also aims to review the natural and forced convective heat transfer characteristics of nanofluids with and without magnetic fields. The discussion for the natural convective heat transfer of nanofluids focuses on the heat transfer performance of non-conventional enclosures and electric heaters. The effects on heat transfer due to variations of heated walls are also investigated. Specific applications of nanofluids in a tube with trapezoidal ribs, double-tube heat exchangers, and plate heat exchangers have been reviewed and presented in a discussion about forced convective heat transfer. The previous results show that the inlet temperature of nanofluids obviously affects the heat transfer characteristics of double-tube heat exchangers, whereas a multi-walled carbon nanotube–water nanofluid shows significant advantages in plate heat exchangers. Finally, this paper studies natural convective heat transfer of magnetic fluids in a square cavity and forced convection heat transfer in a straight tube and a corrugated structure under the action of magnetic fields. It is found that the heat transfer performance of an Fe₃O₄–water nanofluid is enhanced when a magnetic field is applied to the corrugated plate heat exchangers, and the pressure drop can be reduced by around 10%. It is recommended that natural convection of magnetic fluids needs to be investigated experimentally in a real cavity and a corrugated channel under the influence of a magnetic field. In addition, studies of alternating magnetic field are recommended to reveal any improvements of thermal performance of magnetic fluids in heat exchange devices. This review puts forward an effective solution for improvement of the thermal performance of heat transfer equipment and serves as a basic reference for applications of nanofluids in heat transfer fields.

7,987 views

19 citations

TEM images and size distributions of Fe3O4 nanoparticles prepared at different temperatures: (A) 18°C (RT), (B) 35°C, (C) 45°C, (D) 60°C, and (E) 80°C, and the insets represent of particle sizes.

Original Research

24 November 2021

Size Effect of Fe3O4 Nanoparticles on Magnetism and Dispersion Stability of Magnetic Nanofluid

Fang Chen

, 4 more and

Hao Fu

It is well known that magnetic nanofluids are widely applied in various fields ranging from heat transfer to miniature cooling, and from damping to sealing, due to the mobility and magnetism under magnetic field. Herein, the PFPE-oil based magnetic nanofluids with superior magnetization and dispersion stability were obtained via regulating reaction temperature. The structures of particles were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The size effects of particles on the magnetism and coating effect of particles, and on the stability and saturation magnetization of the fluids were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM) and density instrument, respectively. The results indicate that the impurity phase FeOOH only appear in the sample prepared at 18°C and the average size of Fe₃O₄ nanoparticles reduces from 120 to 20 nm with raising reaction temperature. The saturation magnetization of Fe₃O₄ particles increases firstly and then reduces with increasing particle size, which is affected by the thickness of magnetic dead layer and impurity phase FeOOH. The Fe₃O₄ particles could be chemically coated by PFPE-acids, and the coated mass is a little affected by particle size. The stability of the nanofluids lowers while the saturation magnetization increases firstly and then decrease with increasing particle size. At reaction temperature of 60°C, Fe₃O₄ particles of 25 nm and the nanofluids with superior stability and saturation magnetization were obtained. Our results indicate that the control of nanoparticles size by regulating reaction temperature can be a useful strategy for preparing magnetic nanofluids with desirable properties for various potential applications.

5,119 views

25 citations

Original Research

14 December 2021

Numerical Simulation of Magnetic Dipole Flow Over a Stretching Sheet in the Presence of Non-Uniform Heat Source/Sink

Basma Souayeh

, 2 more and

Syed Ghazanfar Hussain

1,474 views

15 citations

Original Research

20 August 2021

Investigation of the Thermal Conductivity, Viscosity, and Thermal Performance of Graphene Nanoplatelet-Alumina Hybrid Nanofluid in a Differentially Heated Cavity

Adeola O. Borode

, 3 more and

Josua P. Meyer

This paper investigates the thermophysical properties and heat transfer performance of graphene nanoplatelet (GNP) and alumina hybrid nanofluids at different mixing ratios. The electrical conductivity and viscosity of the nanofluids were obtained at temperatures between 15–55°C. The thermal conductivity was measured at temperatures between 20–40°C. The natural convection properties, including Nusselt number, Rayleigh number, and heat transfer coefficient, were experimentally obtained at different temperature gradients (20, 25, 30, and 35°C) in a rectangular cavity. The Mouromtseff number was used to theoretically estimate all the nanofluids’ forced convective performance at temperatures between 20–40°C. The results indicated that the thermal conductivity and viscosity of water are increased with the hybrid nanomaterial. On the other hand, the viscosity and thermal conductivity of the hybrid nanofluids are lesser than that of mono-GNP nanofluids. Notwithstanding, of all the hybrid nanofluids, GNP-alumina hybrid nanofluid with a mixing ratio of 50:50 and 75:25 were found to have the highest thermal conductivity and viscosity, enhancing thermal conductivity by 4.23% and increasing viscosity by 15.79%, compared to water. Further, the addition of the hybrid nanomaterials improved the natural convective performance of water while it deteriorates with mono-GNP. The maximum augmentation of 6.44 and 10.48% were obtained for Nu_average and h_average of GNP-Alumina (50:50) hybrid nanofluid compared to water, respectively. This study shows that hybrid nanofluids are more effective for heat transfer than water and mono-GNP nanofluid.

3,275 views

21 citations

The variations of pressure drop at (A)φ = 1%, (B)φ = 2%, and (C)φ = 3%.

Original Research

23 July 2021

The Influence of Combined Turbulators on the Hydraulic-Thermal Performance and Exergy Efficiency of MWCNT-Cu/Water Nanofluid in a Parabolic Solar Collector: A Numerical Approach

Yacine Khetib

, 1 more and

Radi Alsulami

1,563 views

2 citations

Original Research

20 July 2021

Loading PCM Into Buildings Envelope to Decrease Heat Gain-Performing Transient Thermal Analysis on Nanofluid Filled Solar System

Aslam Amirahmad

, 2 more and

Goshtasp Cheraghian

The high share of buildings in energy consumption and carbon dioxide emission has led researchers to seek techniques to reduce energy consumption in this sector. In this study, considering a hot and arid climate region, the wall’s heat gain was investigated. To reduce energy demand, three techniques of adding PCM, combining absorption chiller with a solar system and dispersing nanoparticles were used and the results were evaluated transiently. In July, the addition of PCM to the building's walls reduced the heat exchange between interior and exterior spaces up to 21%. To cool the interior spaces, the combination of absorption chiller + fan coil was used and several flat plate collectors were integrated with it to reduce energy demand. By collecting energy in solar collectors and using a stratified tank, energy consumption in the generator section was reduced by 450 kWh. Nanoparticles were used to improve the solar system performance and it was found that loading ZnO and Al₂O₃ nanoparticles is useful. Dispersing ZnO into water increased the energy-saving by 9.5% while the second nanoparticle improved it by 14.5%.

6,710 views

48 citations

Original Research

23 June 2021

Transient Thermal Analysis of a Solar-Assisted AHU by Focusing on Heat Recovery and Nanoparticles: Jeddah Climate Zone

Yacine Khetib

1,912 views

8 citations