Showing papers by "Josua P. Meyer published in 2021"

Influence of base fluid, temperature, and concentration on the thermophysical properties of hybrid nanofluids of alumina–ferrofluid: experimental data, modeling through enhanced ANN, ANFIS, and curve fitting

Abstract: Recently, the suspension of hybrid nanoparticles in conventional fluids has been investigated as a technique for improving the thermophysical properties of nanofluids. The dearth of documentation on the trio influence of volume concentration, base fluid, and temperature on the electrical conductivity and viscosity of hybrid alumina–ferrofluids [Al2O3–Fe2O3 (25:75 mass%)] has led to this study. The effective viscosity and electrical conductivity of the deionized water (DW)-based and ethylene glycol (EG)–DW-based (50:50 vol%) hybrid alumina–ferrofluids were measured at temperatures of 20–50 °C and volume concentrations of 0.05–0.75%. Based on the importance of soft computing methods to engineers, adaptive neuro-fuzzy inference system (ANFIS) and artificial neural network (ANN) were used for predicting the relative viscosity and electrical conductivity of the two types of hybrid ferrofluids. The measured data for viscosity and electrical conductivity were used in the modeling. Model performances were evaluated using the root mean squared error index. Viscosity was enhanced by 3.23–43.64% and 2.79–49.38%, while electrical conductivity was increased by 163.37–1692.16% and 717.14–7618.89% for the DW- and EG–DIW-based hybrid ferrofluids, respectively, compared with the respective base fluids. Increasing volume concentration augmented the viscosity and electrical conductivity of all the hybrid alumina–ferrofluids, whereas a rise in temperature enhanced their electrical conductivity and detracted the viscosity. DW-based hybrid alumina–ferrofluid was observed to have a lower viscosity and higher electrical conductivity than the EG–DW-based counterpart. The results showed that the optimum ANN and ANFIS models have a maximum error of less than 4.5% and 3.9% for relative viscosity and electrical conductivity, respectively, which were lower than those proposed using regression analysis. With the hybrid alumina–ferrofluids possessing a lower viscosity relative to single-particle ferrofluids, they are recommended for engineering application.

A review of magnetic field influence on natural convection heat transfer performance of nanofluids in square cavities

Abstract: The emergence of nanofluids as high-performance thermal transport media has drawn great research attention in the field of heat transfer. Owning to the huge importance of natural convection applications in environmental, agricultural, manufacturing, electronics, aviation, power plants, and industrial processes, heat transfer and flow characteristics of these special fluids in various cavities have been extensively researched. This review paper has paid serious attention to the benefits of controlling the natural convection heat transfer and flow performance of nanofluids in square cavities using magnetic field sources in addition to the aspect ratio, porous media, cavity and magnetic field inclination, hybrid nanofluids, etc. The influence of several variables such as heat distribution methods, thermal and concentration boundary conditions, governing parameters, magnetic field types, numerical schemes, thermophysical correlation types, nanofluid types, slip conditions, Brownian motion, and thermophoresis on the magnetohydrodynamic (MHD) natural convection behaviours of nanofluids in square cavities has been reviewed. The paper focused on the application of numerical and experimental methods to hydromagnetic behaviours of nanofluids in square-shaped enclosures. The concept of bioconvection, bio-nanofluid (green nanofluid), ionic nanofluid, and hybrid nanofluid has also been reviewed in relation to natural convection for the first time. Special cases of MHD natural convection in cavities involving micropolar and hybrid nanofluids are also presented herein. Convective heat transfer in square cavities has been demonstrated to be altered due to the presence of magnetic fields.

Experimental measurement of viscosity and electrical conductivity of water-based γ-Al2O3/MWCNT hybrid nanofluids with various particle mass ratios

Abstract: The hybridization of nanoparticles is a concept employed for the improvement of the thermal properties of nanofluids. Presently, there is a scarcity of studies in the open literature concerning the influence of particle mass ratios of hybrid nanofluids on the thermal properties. Thus, this paper investigated the effect of temperatures (15–55 °C) and particle mass ratios (90:10, 80:20, 60:40, 40:60, and 20:80) on the viscosity and electrical conductivity of deionized water (DIW)-based γ-Al2O3 and MWCNT hybrid nanofluids. A two-process strategy was deployed to prepare the hybrid nanofluids at a volume concentration of 0.1%. The hybrid nanofluids were characterized for their morphology using a transmission electron microscope. Hybrid nanofluid stability was monitored using UV visible spectrophotometer, viscosity, and visual inspection methods. The prepared nanofluids were observed to be stable with relatively constant viscosity and absorbance values. At 55 °C, maximum enhancements of 442.9% and 26.3%, and 288.0% and 19.3% were recorded for the electrical conductivity and viscosity of Al2O3–MWCNT/DIW nanofluids at particle mass ratios of 90:10 and 20:80, respectively, in relation to DIW. Temperature increase was observed to significantly reduce the viscosity of hybrid nanofluids while the particle mass ratio considerably and positively impacted the electrical conductivity. The relatively low viscosity of the hybrid nanofluids coupled with its reduction under increasing temperature and its insignificance increase as the particle mass ratio of the Al2O3 nanoparticles increased to make them viable coolants for engineering applications. New correlations were proposed to accurately estimate the viscosity and electrical conductivity of the hybrid nanofluids.

Influence of nanoparticles size, per cent mass ratio, and temperature on the thermal properties of water-based MgO–ZnO nanofluid: an experimental approach

Abstract: This paper experiments the trio influence of nanoparticles size (NS), per cent mass ratio (PWR), and temperature (T) on the thermal properties of MgO–ZnO/deionised water (DIW) nanofluids. MgO nanoparticles (20 nm and 100 nm) were hybridised with ZnO nanoparticles (20 nm) and suspended in DIW to formulate 0.1 vol% hybrid nanofluids at PWRs of 20:80, 40:60, 60:40, and 80:20 (MgO/ZnO). The pH, electrical conductivity (σ), viscosity (μ), and thermal conductivity (κ) of the hybrid nanofluids were experimentally determined at temperatures of 20–50 °C. The stability was monitored, while the morphology was examined using standard instruments. Findings showed that the suspension of the hybrid nanoparticles enhanced the pH and thermal properties of DIW. The hybrid nanofluids with 100 nm-MgO nanoparticles were observed to possess slightly higher values of pH, σ, and μ than those with 20 nm-MgO nanoparticles except for κ. An increase in temperature augmented κ and σ of MgO–ZnO/DIW nanofluids, while it detracted pH and μ. Maximum enhancements of 453.70–550.62% (40:60), 14.95–22.33% (40:60), and 8.29–17.46% (60:40) were evaluated for σ, κ, and μ, respectively. The influence of PWR, NS, and temperature on the σ, κ, μ, and pH of the hybrid nanofluids was in the order of PWR > NS > T, NS > PWR > T, T > NS > PWR, and T > NS > PWR, respectively. Subject to the experimental data obtained, correlations were developed for each hybrid nanofluid and thermal property as a function of temperature. The MgO–ZnO/DIW nanofluids with a 40:60 PWR appeared to be the best in terms of heat transfer capability.

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

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.

Experimental Investigation into Natural Convection of Zinc Oxide/Water Nanofluids in a Square Cavity

Abstract: The public domain is inundated with discrepancies in numerical and experimental findings on the natural convection heat transfer performance of nanofluids in a cavity. This paper presents the exper...

Thermodynamics and heat transfer study of a circular tube embedded with novel perforated angular-cut alternate segmental baffles

Abstract: Baffles are used for heat transfer enhancement in heat exchanger tubes. However, they also increase the friction factor in the flow channel. Perforation in baffles further augments the heat transfer. Moreover, it was also noticed that the perforations in the baffles strongly reduce the associated pressure drop in the tube. Some novel ideas for baffles therefore need to be produced, which can cumulatively intensify the performance of the heat exchanger conduit. Therefore, in the present study novel design of perforated angular-cut baffles is considered for the experimental investigation in the turbulent flow regime for thermodynamic and heat transfer investigation. Air is taken as the working fluid with Reynolds number varying from 10,000 to 52,000. Two arrangements of baffles, viz. inline and alternate, are considered for the experimentation. The parameters considered for the investigation are as follows: three perforation ratios (H), two angles of attack, (α) and two pitch ratios (P). The results obtained from the investigation show an enhancement in Nusselt number, Nu, and friction factor, f, both. The highest augmentation in heat transfer is noted for alternate segmental baffles (ASB) with a perforation ratio (H) of 0.15, a pitch ratio (P) of 0.1 and an angle of attack (α) of 45°, while for segmental baffles (SB), a perforation ratio (H) of 0.20, a pitch ratio (P) of 0.2 and an angle of attack (α) of 30° give the minimum heat transfer. An increase in heat transfer coefficient is also noticed with an increase in angle of attack (α). ASB show superior heat transfer compared to SB, and ASB have an enhanced Nu compared to SB for a pitch ratio of 0.1, an angle of attack of 45° and a perforation ratio (H) of 0, 0.15 and 0.2, which is about 39.5%, 37.9% and 42.18%, respectively. Nusselt number, Nu, and friction factor, f, correlations were proposed, and a good agreement was found between the test obtained data and predicted data. The thermo-hydraulic performance parameter for all the examined cases was greater than unity.

Experimental investigation of thermo-convection behaviour of aqueous binary nanofluids of MgO-ZnO in a square cavity

Abstract: An innovative way of advancing thermo-convection performance of thermal management systems is the application of binary nanofluids (BNFs) as thermal working fluids. This paper experimentally investigated for the first time the thermo-convection behaviour of MgO-ZnO nanoparticles dispersed in deionised water (DIW) for concentrations of 0.05 vol.% and 0.1 vol.% at percentage weight ratios (PWRs) of 20:80, 40:60, 60:40, 80:20 (MgO-ZnO) in a square cavity. Several parameters such as Ra, Nuav, hav, and Qav at different temperatures gradients (20°C to 50°C) were investigated. Viscosity and thermal conductivity of the BNFs and DIW were experimentally obtained for the studied temperatures. Temperature gradient and PWRs of hybrid nanoparticles in the BNFs were noticed to enhance Nuav, hav, and Qav. In addition, maximum enhancement achieved were 72.6% (Nuav), 76.01% (hav), and 72.2% (Qav). The use of BNFs in a square cavity proved to yield good enhancement for thermo-convection performance. A new model linked to φand PWRs has been introduced to predict Nuav. The novel outcomes of this study further corroborate the synergetic advantage of using BNFs over NFs.

Thermal–hydraulic efficiency management of spiral heat exchanger filled with Cu–ZnO/water hybrid nanofluid

Abstract: In this paper, the effect of different channel spacing in spiral heat exchanger filled with Cu–ZnO–water hybrid nanofluid was investigated to find the optimum thermal–hydraulic performance. The hot water flow enters into the test section from central aperture of heat exchanger, and the cold hybrid nanofluid flow enters into the test section from the outer aperture of the heat exchanger. The effects of different flow velocities, nanoparticles φ and channel spacing values have been analyzed. Results have been presented on Nusselt number, outlet temperature, pressure drop and PEC. According to the obtained results, channel spacing decrease in constant flow velocity values is more effective than volume fraction increase on outlet temperature improvement. Also, an increase in inlet flow velocity leads to lower heat transfer between cold and hot channels, but the growth of volume fraction can improve the thermal efficiency of the heat exchanger at high velocities. On the other hand, the reduction in channel spacing leads to more pressure drop penalty. Especially for the hot water flow, this behavior reduces the hydraulic performance of heat exchanger. The less the channel spacing, the more the pressure drop. The highest average Nusselt number occurs at a velocity of 0.45 (m s−1) and φ = 4% at a channel spacing of 35 mm. The maximum value of the pressure drop occurs at b = 2.5–5 mm. Besides considering the PEC value, 2% volume fraction is recommended for the spiral heat exchanger.

Modelling of heat transfer coefficients during condensation inside an enhanced inclined tube

Abstract: In this study, experiments were conducted for the flow of R-134a condensing in an enhanced inclined tube at a saturation condensing temperature of 40 °C. The enhanced tube had a helix angle of 14° with a mean internal diameter of 8.71 mm. The mass velocities were varied from 200 to 600 kg m−2 s−1, while the inclination angles were varied from − 90° to + 90°. It was found that the inclination angle had a considerable effect on the flow patterns and the thermal performance. It was also found that the maximum heat transfer coefficients were obtained at tube inclinations of between − 15° and − 5° (downward flows). By using the experimental data and artificial neural networks (ANN), a model was proposed to predict the heat transfer coefficients during condensation inside the enhanced inclined tube. By using four statistical criteria, the performance of the proposed model was examined against experimental data, and it was found that ANN was a useful tool for the prediction of the heat transfer coefficients based on the effective parameters of vapour quality, mass velocity and inclination angle.

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

Abstract: This paper investigates the thermophysical properties and heat transfer performance of GNP-alumina hybrid nanofluids at different mixing ratios. The electrical conductivity and viscosity of the nanofluids were obtained at temperatures between 15 – 55oC. The thermal conductivity was measured at temperatures between 20 – 40oC. The natural convection properties, including Nusselt number, Rayleigh number, and heat transfer coefficient, were experimentally obtained at different temperature gradients (20, 25, 30, and 35oC) in a rectangular cavity. The Mouromtseff number was used to theoretically estimate all the nanofluids’ forced convective performance at temperatures between 20 – 40oC. 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 Nuaverage and haverage 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.

Effect of Various Surfactants on the Viscosity, Thermal and Electrical Conductivity of Graphene Nanoplatelets Nanofluid

Abstract: The effects of surfactants on the stability and thermophysical properties of graphene nanoplatelets nanofluids are experimentally studied at different temperatures. Graphene nanoplatelets (GNP) nanofluids were prepared with various surfactants, including sodium dodecylbenzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), Gum Arabic (GA), and Tween 80 at different GNP-surfactant ratios (2:1, 1:1, and 1:2). The best dispersion and stabilization over 2 weeks was found to be with a GNP-surfactant ratio of 2:1 for SDBS-based nanofluids and 1:1 for nanofluids with other surfactants. A comparative study of the effects of the different surfactants on the electrical conductivity, pH, thermal conductivity, and viscosity was carried out. The study observed that all nanofluids’ electrical conductivity and thermal conductivity are augmented at elevated temperatures while the pH and viscosity deteriorate at higher temperatures. The electrical conductivity measurements of the GNP nanofluids show that SDBS addition contributes the highest enhancement of 154.33 % compared to water. This was followed by SDS, GA, and Tween 80-based nanofluid, which has an electrical conductivity enhancement of 153.25 %, 21.48 %, and 2.83 %, respectively. In comparison to water, the thermal conductivity results revealed that SDBS, GA, SDS, and Tween 80-based nanofluid has a maximum enhancement of 5.50 %,5.66 %, 6.45 %, and 8.96 %, respectively, at 45 °C. This shows that a higher thermal conductivity enhancement is achieved using Tween 80 as the dispersant. The experimental results further revealed that the viscosity of the nanofluids greatly increased with the use of GA compared to other surfactants. Compared to water, a maximum viscosity increase of 5.79 %, 17.54 %, 19.30 %, and 22.81 % was obtained for SDBS-GNP, GA-GNP, SDS-GNP, and Tween 80-GNP, respectively at 55 °C.

A Computational Fluid Dynamic Study on Efficiency of a Wavy Microchannel/Heat Sink Containing Various Nanoparticles.

Abstract: In this paper, a common and widely used micro-heat sink (H/S) was redesigned and simulated using computational fluid dynamics methods. This H/S has a large number of microchannels in which the walls are wavy (wavy microchannel heat sink: WMCHS). To improve cooling, two (Al2O3 and CuO) water-based nanofluids (NFs) were used as cooling fluids, and their performance was compared. For this purpose, studies were carried out at three Reynolds numbers (Re) of 500, 1000, and 1500 when the volume percent (φ) of the nanoparticles (NPs) was increased to 2%. The mixture two-phase (T-P) model was utilized to simulate the NFs. Results showed that using the designed WMCHS compared to the common H/S reduces the average and maximum temperatures (T-Max) up to 2 °C. Moreover, using the Al2O3 NF is more suitable in terms of WMCHS temperature uniformity as well as its thermal resistance compared to the CuO NF. Increasing the φ is desirable in terms of temperature, but it enhances the pumping power (PP). Besides, the Figure of Merit (FOM) was investigated, and it was found that the value is greater at a higher volume percentage.

Convection Heat Transfer, Entropy Generation Analysis and Thermodynamic Optimization of Nanofluid Flow in Spiral Coil Tube

Abstract: In this study, heat transfer, flow characteristics, and entropy generation of turbulent TiO2/water nanofluid flow in the spiral coil tube were analytically investigated considering the nanoparticle...

Study on the Effect of Hole Size of Trombe Wall in the Presence of Phase Change Material for Different Times of a Day in Winter and Summer

Abstract: In this article, a numerical study is performed on a Trobme wall in a tropical city for two seasons, summer and winter. A 1×1.5 m Trobme wall with a thickness of 15 cm is designed and analyzed. A 1-inch-diameter tube filled with PCM is used to enhance efficiency. The wall is analyzed at different times of the day for the two cold and hot seasons for different sizes of wall holes in the range of 70 to 17.5 cm when the wall height is 20 cm. A fluid simulation software is employed for the simulations. The problem variables include different hours of the day in the two cold and hot seasons, the presence or absence of PCM, as well as the size of the wall hole. The results of this simulation demonstrate that the maximum outlet temperature of the Trobme wall occurs at 2 P.M. Using PCM on the wall can allow the wall to operate for longer hours in the afternoon. However, the use of PCM reduces the outlet wall temperature in the morning. The smaller the size of the wall hole, the more air can be expelled from the wall.

Modeling Of Heat Transfer Coefficients During Condensation At Low Mass Fluxes Inside Horizontal And Inclined Smooth Tubes

Abstract: In this study, in-tube condensation was conducted for mass fluxes of 100, 75 and 50 kg/m2s, and temperature differences of 1, 3, 5, 8 and 10 °C. Measurements and flow regimes were captured at vario...

On numerical investigation of heat transfer augmentation of flat target surface under impingement of steady air jet for varying heat flux boundary condition

Abstract: The prediction of flow pattern for the proposed range of Reynolds number and nozzle–target spacing is carried out using SST + Gamma–Theta turbulence model. The simulations of the flow field in a computational domain are carried out using CFX as a base solver with $$10^{-6}$$ being the converging criteria. The present work aims to determine the local Nusselt number magnitude for varying heat flux input boundary conditions. Not only this, the impinging Reynolds numbers and nozzle–target spacing are also varied to record sufficient data, enough to predict a semi-empirical correlation. The proposed correlation for calculating the cooling characteristic (Nusselt number magnitude) under the impingement of air jet is presented in terms of profile heat flux parameter, impinging Reynolds number, and target to nozzle exit spacing. The corresponding mathematical parameter representing the profile heat flux boundary condition is the slope in heat flux magnitude versus the target surface's radial distance. The Nusselt number profile, which describes the cooling characteristic under different impinging Reynolds numbers and nozzle–target spacing, initially increases, takes a peek, and decreases. The rise in the cooling rate near the stagnation region is due to the turbulence palpitation, resulting from imbalance adverse pressure gradient and onset transition of Reynolds number. The local heat transfer under such boundary conditions increases with nozzle–target spacing and least depends on Reynolds number. However, the Nusselt profile for a constant heat flux magnitude but varying slope (non-uniform) shows an enhancement with a decrease in the slope from unit value.