Thermal Conductivity Ratio Research Articles

COMPARISON OF THERMOPHYSICAL PROPERTY MODELS OF NANOFLUIDS FOR THERMAL PERFORMANCE IN A MICROCHANNEL

Different thermophysical property models for nanofluids and several dimensionless parameters have been compared in the case of heat transfer for laminar flow in a microchannel. Addition of nanoparticles, including Al<sub>2</sub>O<sub>3</sub>, CuO, and TiO<sub>2</sub>, to water has been considered for volumetric concentrations up to φ = 7%. The numerical analyses have been conducted via the finite difference method for a transient regime. The heat transfer results have been obtained in terms of the interfacial heat flux, bulk temperature, and the Nusselt number. The parametrical effects of Péclet number values, wall thickness ratios, thermal diffusivity ratios, thermal conductivity ratios, and Brinkman number values have been evaluated. Based on the results, the influence of axial conduction has been clearly observed for lower Péclet numbers. Furthermore, the increment of the thermal conductivity ratio and the decrement of the wall thickness ratio have enhanced thermal performance. Nevertheless, the thermal characteristics have not been significantly influenced by the thermal diffusivity ratio. The viscous dissipation has altered the heat transfer direction due to the change in the Brinkman number. The required time to reach the steady state for numerical solution increased because of decreasing Brinkman number values. Heat transfer augmentation has been obviously obtained due to ascending nanofluid volumetric concentrations. The CuO nanoparticles have been recommended owing to their higher thermal performance for the fixed volumetric concentration. According to the thermophysical models compared for each type of nanoparticles, the models for Al<sub>2</sub>O<sub>3</sub> nanoparticles presented the closest results to each other. Nonetheless, it has been observed that one model for CuO nanoparticles and one model for TiO<sub>2</sub> nanoparticles are inadequate.

Effective Thermal Conductivity of Cyclohexane-Based Nanofluids Containing Cerium Dioxide Nanoparticles with Chemisorbed Organic Shell

In the present study, the effective thermal conductivity λeff of nanofluids containing metal oxide nanoparticles with a chemisorbed organic shell was investigated experimentally and theoretically. The model systems synthesized by a continuous-flow hydrothermal method consist of cyclohexane as organic base fluid and dispersed nearly spherical cerium dioxide (CeO2) core nanoparticles with a decanoic acid shell chemically attached to their surface. From the differences between the hydrodynamic diameters of the two core–shell nanoparticle types with (8.6 or 9.1) nm determined by dynamic light scattering (DLS) and the nearly spherical CeO2 core diameters obtained by analytical ultracentrifugation (AUC) and transmission electron microscopy (TEM), an estimation for the thickness of the entire hydrodynamic layer around the particle core in the range of about (1.1 to 1.3) nm could be deduced. Experimental data for λeff of the nanofluids and the thermal conductivity of the base fluid λbf were determined with a steady-state guarded parallel-plate instrument (GPPI) with an expanded (k = 2) relative uncertainty of 0.026 at atmospheric pressure over a temperature range from (283.15 to 313.15) K in steps of 10 K. The measurement results for the thermal-conductivity ratio λeff ·λbf–1 are independent of temperature and increase with increasing volume fraction of the CeO2 core nanoparticles up to about 0.023. It was found that the experimental results can be described by the Hamilton–Crosser model within their experimental uncertainties for all temperatures investigated.

Experimental and explainable machine learning approach on thermal conductivity and viscosity of water based graphene oxide based mono and hybrid nanofluids

This study explores the thermal conductivity and viscosity of water-based nanofluids containing silicon dioxide, graphene oxide, titanium dioxide, and their hybrids across various concentrations (0 to 1 vol%) and temperatures (30 to 60 °C). The nanofluids, characterized using multiple methods, exhibited increased viscosity and thermal conductivity compared to water, with hybrid nanofluids showing superior performance. Graphene oxide nanofluids displayed the highest thermal conductivity and viscosity ratios, with increases of 52% and 177% at 60 °C and 30 °C, respectively, for a concentration of 1 vol% compared to base fluid. Similarly, graphene oxide-TiO2 hybrid nanofluids achieved thermal conductivity and viscosity ratios exceeding 43% and 144% compared to the base fluid at similar conditions. This data highlights the significance of nanofluid concentration in influencing thermal conductivity, while temperature was found to have a more pronounced effect on viscosity. To tackle the challenge of modeling the thermophysical properties of these hybrid nanofluids, advanced machine learning models were applied. The Random Forest (RF) model outperformed others (Gradient Boosting and Decision Tree) in both the cases of thermal conductivity and viscosity with greater adaptability to handle fresh data during model testing. Further analysis using shapely additive explanations based on cooperative game theory revealed that relative to temperature, nanofluid concentration contributes more to the predictions of the thermal conductivity ratio model. However, the effect of nanofluid concentration was more dominant in the case of viscosity ratio model.

BIOT NUMBER ERROR IN LOW TEMPERATURE INCONEL OVERALL EFFECTIVENESS EXPERIMENTS

Abstract To predict the performance of turbine materials at engine conditions, experiments are performed at lower temperature laboratory conditions. To ensure the results accurately predict the nondimensionalized surface temperature, the Biot number must be matched, requiring the ratio of the thermal conductivity of the material to that of air is matched. With alloys such as Inconel, it is sometimes assumed that the Biot number is matched since Inconel's thermal conductivity variation scales similarly to that of air. However, the thermal conductivity ratio does not scale perfectly sosome Biot number error exists, with the problem exacerbated at lower temperatures. To date, there has been no quantification of the error in the overall effectiveness, ϕ, that might be caused by this Biot number error. Ti-6Al-4V is predicted to allow for a better Biot number match, better simulating Inconel at engine conditions in a low temperature experiment. In this research, we utilized geometrically identical models constructed of Ti-6Al-4V and Inconel 718 to evaluate the error in ϕ that might occur through using an actual engine nickel alloy part at experimental conditions. While the Ti-6Al-4V model has nearly perfectly matched Biot number, the Inconel model's value was 73% higher. The theoretically more Biot number appropriate Ti-6Al-4V model produced area averaged ϕ values that differed by only 0.01 from its Inconel counterpart. These results suggest that typical nickel superalloy turbine components may be tested at low temperature without the use of a surrogate material.

Effects of Solid-to-Fluid Conductivity Ratio on Thermal Convection in Fluid-Saturated Porous Media at Low Darcy Number

Abstract This study presents experimental data on the effects of the solid-to-fluid thermal conductivity ratio on natural convective heat transfer in a fluid-saturated porous medium heated from below. Argon is used as the saturating fluid, while a bed of glass, steel, or aluminum spheres constitutes the solid porous matrix. Emphasis is placed on attaining high Rayleigh numbers while maintaining low Darcy numbers (5.68 × 10−8 ≤Da≤5.22 × 10−7). At low modified Rayleigh numbers (Ra*) corresponding to the Darcy regime, the Nusselt number is independent of the medium conductivity. As Ra* increases and the system transitions into Forchheimer regime, the data diverge, with Nusselt numbers decreasing with increased thermal conductivity ratio at a fixed Ra*. This non-intuitive result is shown to be the result of the traditional choice of Ra* and Da as the controlling parameters since the heat transfer coefficient appears independent of the conductivity ratio. Scaling arguments are used to identify transition points between the regimes, which yield the transition criterion Ra* ~ Prp, where Prp is the modified Prandtl number. When the data are expressed by scaling with Prp, it is shown that the data for multiple parameter combinations collapse onto a single curve, which also agrees well with theoretical predictions. In light of this finding, the data from available literature are assessed, and it is proposed that deviations from theory are likely the result of the strong porous medium condition (low Da) not being satisfied.

Effect of Phenolic Resin Pyrolysis on Thermal Properties of SiFRP Composites under High Heating Rates

Abstract During the ablation process of resin-based composite materials, residual carbon generated from pyrolysis of phenolic resin change the thermal performance of the material. Phenolic resin pyrolysis process depends on temperature and heating rate. Based on the mass loss curves of phenolic resin under high heating rates (5K/s, 50K/s, 100K/s), the study analyzes the variations in thermal performance parameters of SiFRP composite materials with temperature assuming phenolic resin and silica fibres are in parallel in heat transferring. As temperature rising, the pyrolysis conversation ratio of phenolic resin increases, thermal conductivity and specific heat capacity of the composites increase accordingly. The greater the heating rates, the smaller the change of thermal conductivity and specific heat capacity of composites at the same temperature. The complete pyrolysis temperature of phenolic resin is positively correlated with the temperature rise rate. When the temperature rise rate is very large (such as 100K/s), the influence of pyrolysis on the thermal properties of composites can be ignored at medium and low temperature.

Viscous dissipation impacts on a developing thermal field in a saturated porous medium: An effective thermal management

In this study, we investigate the impacts of two viscous dissipation models—the form drag (FD) model and the clear fluid compatible (CFC) model—on the thermal behavior of fluid flow within a porous medium in a parallel plate channel. We analyze temperature distributions under constant heat flux conditions by employing the local thermal non-equilibrium model and assuming unidirectional flow governed by the Darcy–Brinkman model. Our results indicate that an increase in the Brinkman number, Biot number, and thermal conductivity ratio enhances the temperature distribution. Notably, the CFC model demonstrates a higher local Nusselt number compared to that in the FD model, highlighting its potential for applications in heat exchanger design where efficient heat transfer is crucial. Our analysis aids in predicting thermal performance and efficiency, emphasizing the importance of selecting appropriate viscous dissipation models to achieve optimal thermal outcomes. The findings have significant applications in thermal management technologies. A comparative analysis with experimental and computational studies further strengthens these insights, making them applicable to a wide range of thermal systems (see Sec. V B). This study can assist engineers in accounting for viscous dissipation when designing systems that involve fluid flow through porous media, such as heat exchanger devices, particularly in the entrance region of ducts, where the thermal field begins to develop.

Thermal Conductivity and Thermal Hall Effect in Dense Electron-Ion Plasma

In this study, we examine thermal conductivity and the thermal Hall effect in electron-ion plasmas relevant to hot neutron stars, white dwarfs, and binary neutron star mergers, focusing on densities found in the outer crusts of neutron stars and the interiors of white dwarfs. We consider plasma consisting of single species of ions, which could be either iron [56]Fe or carbon [12]C nuclei. The temperature range explored is from the melting temperature of the solid T∼109 K up to 1011 K. This covers both degenerate and non-degenerate electron regimes. We find that thermal conductivity increases with density and temperature for which we provide analytical scaling relations valid in different regimes. The impact of magnetic fields on thermal conductivity is also analyzed, showing anisotropy in low-density regions and the presence of the thermal Hall effect characterized by the Righi–Leduc coefficient. The transition froma degenerate to non-degenerate regime is characterized by a minimum ratio of thermal conductivity to temperature, which is analogous to the minimum observed already in the case of electrical conductivity. We provide also formulas fit to our numerical results, which can be used in dissipative magneto-hydrodynamics simulations of warm compact stars.

Thermo-economic performance analysis and multi-objective optimization of viscosity ratio and thermal conductivity ratio of copper oxide–palm oil nanolubricants

Through experimental research, this work explores the thermophysical properties, cooling efficiency, and economic viability of copper oxide–palm oil nanolubricants in tribology applications. The viscosity and thermal conductivity of the nanolubricants were tested at three different volume concentrations (0.1, 0.3, and 0.5 vol. %) throughout a temperature range of 30 °C to 80 °C at intervals of 10 °C. Researchers looked attentively at how the viscosity and thermal conductivity ratios of the nanolubricants were affected by temperature and volume concentration. A significant increase in thermal conductivity was noted with increasing concentration and temperature. On the other hand, as temperature increased, viscosity reduced and was dependent on volume concentration. The property enhancement ratio was used to evaluate the nanolubricants' cooling capacity before an economic analysis of their cooling efficacy was conducted. Based on experimental data, the study led to the creation of novel correlations between the viscosity ratio and thermal conductivity ratio. These models showed a high degree of agreement (R2 values of 99.47% for the thermal conductivity ratio and 97.78% for the viscosity ratio) between the expected and actual outcomes. The ideal values of the viscosity and thermal conductivity ratios were 1.10 and 1.62, respectively. These values corresponded to a critical temperature of 37.32 °C and a volume concentration of 0.16 vol. % for nanoadditives. The findings offer valuable insights into optimizing nanolubricants for enhanced cooling performance in tribological systems, with potential applications in improving energy efficiency and reducing operational costs in industrial processes.

Both edge substitution effects on thermal conductivity of armchair graphene nanoribbons under tensile strain: From equilibrium molecular dynamics simulations

Thermal conductivity and phonon spectra change of graphene nanoribbon as function of both side edges substitution and strain is investigated using equilibrium molecular dynamics. Under small strain, the edge’s partial substitution by graphane plays effect role to change the phonon mode of GNR. Under large tensile strain, reduction ratio of thermal conductivity is the largest in case of fluorographane hybrid and the smallest in case of graphane hybrid. Especially, under 16 % strain, the thermal conductivity of GNR is reduced until 13 % by edges substitution of graphane. The phonon spectra shift peaks towards low frequency at high frequency range (>50 THz).

Analysis of thermal performance and irreversibility of double-diffusive buoyancy-driven nano-suspension subject to local thermal non-equilibrium model

In fact, local thermal equilibrium (LTE) would be unsuitable when it comes to nuclear reactors, electronic equipment, space devices, geothermal engineering, and high-conductivity foams, due to prominent temperature discrepancy between the two constituents (solid and nanofluid) in porous material. Local thermal non-equilibrium (LTNE) situation may be considered in above real world applications. In view of above relevance, the effects of LTNE model on double-diffusive natural convection (DDNC) within a fluid-saturated porous container loaded with the TiO2-H2O nanofluid and emplacing four cooling and hot channels in Forchheimer-Brinkman-extended Darcy medium have been investigated in the present study. The momentum, heat and mass equations are solved by finite element method. Irreversibility in the two constituents (nanofluid and solid) of the porous structure has been analyzed. The significant outcomes are that fluid circulations enhance due to rise in porosity of the medium. Fluid friction entropy EnFF,T ameliorates significantly by 1514.16 % and 872.97 % with increase in Rayleigh number and porosity of the medium. It is clear that Nuloc,nf,Nuave,nf, Nuloc,s&Nuave,s enhance significantly with rise of buoyancy and thermal conductivity ratio, interstitial solid/fluid heat transfer coefficient.

Thermal conductivity of 3D-printed block-copolymer-inspired structures

This study primarily focuses on examining the impact that geometric structure has on thermal conductivity of multi-phase constructs in different 3D-printed poly(lactic acid), PLA, samples. The investigated structures are inspired by morphologies formed by diblock copolymers: lamellae, hexagonally packed cylinders, and gyroid. This research also investigates how volume percentage and material combination influence the thermal conductivity of these structures. The samples can be tailored to simulate various thermal management structures observed in practical applications, such as thermal interface materials in electronic devices. Thermal conductivity ratio is controlled using air, the least conductive material at 0.026 W/(m K), PLA at 0.136 W/(m K), and thermal paste at 5.11 W/(m K). Different models were tested against thermal conductivity measurements in order to capture the effect of material type (PLA-Air versus PLA-Thermal Paste), volume percentage, structure, and orientation. Simple, effective medium models were good predictions of thermal conductivity in lamellar structures, but it was necessary to develop models for conduction through cylindrical and gyroid structures. Finally, all results were normalized to find a universal model that is independent of structure and material. This approach provides a simple method to predict how to reduce or enhance transport properties and heat management capabilities of 3D printed objects.

Convective heat transfer in porous channel with multi-layer fractures under Local thermal non-equilibrium condition

Based on Brinkman-extended-Darcy model and Local thermal non-equilibrium (LTNE) model, analytical solutions of velocity and temperature fields, pressure drop and Nusselt number of porous channels containing different number of fracture layers are obtained. The characteristics of fluid flow and heat transfer in multi-layer parallel fractured channels are further studied. Results show that for a single-layer or multi-layer fractured channel, the pressure drop changes sensitively at small hollow ratio and increases as the number of fracture layers increases with decreasing increase degree, but the pressure drop tends to be consistent regardless of the number of fracture layers when Darcy number is high. For small ratio of effective thermal conductivity, LTE model is valid regardless of Biot number, and the heat transfer intensity in multi-layer fractured channels is always higher than that in single-layer fractured channel at any hollow ratio, but the heat transfer intensity is still low. For large ratio of effective thermal conductivity, increasing Biot number or fracture layer number makes the Nusselt number increase under very small hollow ratio for both single and multiple fracture cases, and when both the ratio of effective thermal conductivity and Biot number are high, there is an intersection point occurs at hollow ratio near 0.1, which makes same heat transfer effect under different fracture numbers.

Effects of viscous dissipation, temperature dependent thermal conductivity, and local thermal non‐equilibrium on the heat transfer in a porous channel to Casson fluid

AbstractThe current paper deals with viscous dissipation effects in a permeable (or porous) channel filled with non‐Newtonian Casson fluid by considering the local thermal non‐equilibrium (LTNE) model. The dependency of the effective thermal conductivities of the solid and fluid phases on the respective temperatures has been studied along with the spatially varying Biot number. The Brinkman number Casson fluid parameter , thermal conductivity variation parameter , porosity Darcy number , and the ratio of fluid and solid phase thermal conductivities are the main governing parameters. The Darcy–Brinkman model is employed to govern the fluid flow in permeable media and the velocity profile has been obtained analytically. Moreover, the energy equations for both phases along with suitable boundary conditions are derived and solved with the fourth order boundary value solver. The findings of the current study depict that the Nusselt number increases with the increment in Casson fluid parameter and decreases with the increment in Brinkman number and thermal conductivity variation parameter. Overall, the heat transmission between the solid and fluid phases increases with the decrement in Brinkman number and thermal conductivity variation parameter. On the other hand, the heat transmission between both the phases magnifies by increasing the value of Casson fluid parameter.

Numerical analysis of transient MHD natural convection in a channel with four heat-generating cylindrical solids filled with in a non-Newtonian Fe3O4 ferrofluid

This article presents a numerical investigation and analysis of the cooling effectiveness of thermomagnetic transient natural convection in a long channel, equipped with four cylindrical heat-generating blocks. A non-Newtonian power-law ferrofluid was employed for the present investigation to achieve optimum cooling. The governing equations are the continuity equation, the momentum equation and the energy equation. The finite volume method was used to solve the resulting algebraic system. From an energy-saving point of view, this configuration can provide a good approximation for selecting effective physical and geometrical parameters to design a reliable thermal system. For this purpose, the study was carried out for various geometric and thermophysical parameters. Different values of thermal conductivity, power law index, Rayleigh number, Hartmann number and ferrofluid volume fraction, were considered. The results are illustrated in the form of streamlines, isotherms, average Nusselt and a spatio-temporal characterization of the mean ferrofluid velocity. From the results presented, we can conclude that the choice of non-Newtonian, pseudoplastic ferrofluid with a low thermal conductivity ratio subjected to a uniform magnetic field proves to be a crucial solution for efficient and stable cooling of heat-generating cylindrical blocks, which will have to be close to the cold walls of the channel.

The influence of fracture connectivity on heat extraction performance of geothermal doublet systems based on a coupled thermo-hydro-mechanical model

The fracture connectivity in enhanced geothermal systems plays a vital role in the process of heat extraction. In this paper, a coupled thermo-hydro-mechanical model with discrete fractures is developed to investigate the influence of fracture connectivity on the heat extraction performance of a geothermal doublet system. The proposed model adopts the assumptions of a one-dimensional fracture element and thin elastic layer. The influences of spacing or connectivity of two discrete fractures on heat extraction efficiency are investigated under varying thermal conductivity and permeability ratios. The evolutions of fracture aperture, production temperature, and heat extraction rate are analyzed. The simulations indicate that the key factors influencing thermal recovery, listed in order of decreasing impact, are the permeability ratio, fracture connectivity, and bedrock thermal conductivity. When the permeability ratio exceeds 10−6, thermal convection becomes the dominant factor, thereby diminishing the impact of fracture connectivity. In contrast, when the bedrock thermal conductivity is greater than 3 W/(m·K), thermal conduction takes precedence, and the efficiency of geothermal heat extraction is enhanced by the preferential flow paths resulting from fracture connectivity. The research results have important guiding significance for the optimization design of production strategy in the heat extraction process of enhanced geothermal reservoirs.

Magnetohydrodynamic convection in a heat-generating ferrofluid within a corrugated cavity containing a rotating cylinder

This study introduces a novel approach by combining magnetohydrodynamic flow with Joule heating effects to investigate the conjugate mixed convective flow of ferrofluid in a non-homogenously warmed wavy-walled squared-shaped chamber with a spinning cylindrical object positioned at the center of the chamber. The current study seeks to maximize heat transmission effectiveness by scrutinizing optimum system attributes and conducting entropy production analysis. Numerical solutions are achieved by employing the Galerkin finite element weighted residual approach to solve the two-dimensional Navier–Stokes and heat energy equations representing the mathematical model. The parametric alterations encompass Grashof (103 ≤ Gr ≤ 106), Reynolds (31.62 ≤ Re ≤ 1000), and Hartmann (5.623 ≤ Ha ≤ 31.623) numbers, volumetric heat generation coefficient (0 ≤ Δ ≤ 10), thermal conductivity ratio (K = 20.07, 95.14), corrugation frequency (6.5 ≤ f ≤ 8.5), dimensionless corrugation amplitude (0.02 ≤ A ≤ 0.04), and dimensionless cylinder diameter (0.3 ≤ D ≤ 0.5). The study assesses the thermal characteristics of a heat source and the entropy generated within the computational domain while considering varying corrugation frequency and amplitude, cylinder diameter, thermal conductivity, strength of magnetism, and heat generation. The findings are quantitatively showcased through the Nusselt number of the hot wall, mean fluid temperature, overall entropy production, and thermal performance criterion (TPC) across the domain. After extensive analysis, it is evident that minimum cylinder diameter (= 0.3), corrugation frequency (= 6.5), and amplitude (= 0.02) while the maximum thermal conductivity ratio (= 95.14) ensure optimal system performance. Surprisingly, incorporating interior heat production diminishes thermal performance significantly while increasing TPC. Understanding the impacts of the magnetic field, Joule heating, and interior heat production on convective flow offers key perceptions into temperature variation, heat transport, velocity profile, and irreversible energy loss in numerous engineering applications.

A robust lattice Boltzmann scheme for high-throughput predicting effective thermal conductivity of reinforced composites

Accurately predicting effective thermal conductivity is of great importance for the design and performance evaluation of emerging composites. In this paper, an efficient and implementation-friendly lattice Boltzmann (LB) scheme for predicting the effective thermal conductivity of 3D complex structures is proposed. The key innovation is that the optimum convergence parameter of the 3D thermal LB method is found, which enables the LB equation to converge to steady heat conduction equation with the fastest speed and without losing any accuracy. To deal with the thermal contact resistance between different components, an interface treatment scheme is derived. In comparison with the existing schemes, the present scheme enjoys several hundred times higher computational efficiency. By virtue of this LB scheme, the effective thermal conductivity of the reinforced composites with different dimensional fillers are systematically calculated, and a comprehensive machine learning model is developed. This work provides a powerful numerical tool for high-throughput simulations of the 3D representative volume elements with high thermal conductivity ratios and large grid numbers. It may facilitate the application of data-driven techniques in study of the thermal transport properties of emerging composite materials and structures.

Influence of periodicity on natural convection in a square porous cavity due to non-uniform heat under LTNE state

In this article, the influence of the local thermal non-equilibrium (LTNE) state on free convection in a square cavity filled with fluid-saturated porous medium is investigated numerically. The steady-state flow is induced due to sinusoidal heat distributed on the side walls of the cavity and insulated of the horizontal walls. The coupled flow governing equations are solved numerically by using the finite volume method (FVM) consisting of the SIMPLER (Semi-Implicit Method for Pressure Linked Equation Revised) Algorithm. The numerical simulations of temperature and stream-function contours are carried out for the non-Darcy model. The developed code is validated with existing numerical and present computed results for the case of a square enclosure associated with non-uniform heat source. Then, the present numerical results are analyzed over a range of physical parameters, like periodicity parameter ( N ≥ 1 ), interface heat transfer coefficient ( 10 − 2 ≤ H ≤ 10 2 ), porosity scaled thermal conductivity ratio ( 10 − 2 ≤ γ ≤ 10 2 ), with a fixed Rayleigh number ( Ra = 10 6 ), Darcy number ( Da = 10 − 4 ), Prandtl number (Pr = 0.71), and porosity ( ε = 0.8 ). To study the impacts of these key parameters on the fluid flow behavior and isotherm patterns of fluid as well as solid phase in the porous-square enclosure. From present numerical experiments that the structure of flow is controlled by multicellular structure with rotating clockwise and anticlockwise directions in the entire results. The flow dynamics are highly affected by the periodicity parameter (N) under LTNE circumstances. The characteristics of the local Nusselt number have the point of inflection and the maximum magnitude of it increases with N. The significant effect of H is found on the heat transfer rate of fluid phase but it is negligible on the heat transfer rate of solid phase. However, the influence of γ is found reverse in nature on the heat transfer rate of fluid as well as solid phase when as compared to the effect of H.

Experimental study on preparation and heat transfer efficiency of ethylene glycol/water-based hybrid nanofluids enhanced by graphene oxide/MXene nanoparticles

In this study, the preparation and heat transfer efficiencies of ethylene glycol (EG)/water-based (50:50) hybrid nanofluids were enhanced using graphene oxide (GO)/MXene (1:1) nanoparticles. The stability of the nanofluids was analyzed, and the thermal conductivity and viscosity were tested at 20–60 °C. A correlation equation for the thermal conductivity ratio of the nanofluids was proposed. The heat transfer efficiency of the nanofluids was evaluated using the performance enhancement ratio (PER) and Mouromtseff number (Mo). The prepared EG/water-based GO/MXene nanofluids exhibited good chemical and dispersion stability. The thermal conductivity and viscosity of the nanofluids gradually increased with the GO/MXene dosage. The nanofluid containing 0.3 wt% GO/MXene nanoparticles exhibited the largest thermal conductivity increment of 33.49 % at 60 °C compared with EG/water and maintained the low viscosity. The proposed prediction equation based on the temperature and mass dosage was highly accurate. The PER and Mo demonstrated the suitability of the GO/MXene nanofluids for heat transfer applications.