This paper presents a steady-state heat transfer model for the natural convection of mixed Newtonian-Non-Newtonian (Alumina-water) and pure non-Newtonian (Alumina-0.5 wt% Carboxymethyl Cellulose (CMC)/water) nanofluids in a square enclosure with adiabatic horizontal walls and isothermal vertical walls, the left wall being hot and the right wall cold. In the first case, the nanofluid changes its Newtonian character to non-Newtonian past 2.78% volume fraction of the nanoparticles. In the second case, the base fluid itself is non-Newtonian and the nanofluid behaves as a pure non-Newtonian fluid. The power-law viscosity model has been adopted for the non-Newtonian nanofluids. A finite-difference based numerical study with the Stream function-Vorticity-Temperature formulation has been carried out. The homogeneous flow model has been used for modeling the nanofluids. The present results have been extensively validated with earlier works. In Case I, the results indicate that Alumina-water nanofluid shows 4% enhancement in heat transfer at 2.78% nanoparticle concentration. Following that there is a sharp decline in heat transfer with respect to that in base fluid for nanoparticle volume fractions equal to and greater than 3%. In Case II, Alumina-CMC/water nanofluid shows 17% deterioration in heat transfer with respect to that in base fluid at 1.5% nanoparticle concentration. An enhancement in heat transfer is observed for increase in hot wall temperature at a fixed volume fraction of nanoparticles, for both types of nanofluid.

This paper presents a numerical investigation on heat transfer and flow behavior for non-Newtonian nanofluids with different nanoparticles (Al 2 O 3 and CuO) and carboxymethyl cellulose (CMC) with water as a base fluid. The analysis has been carried out in an elliptical tube. Power-law model is adopted to depict the non-Newtonian nature of nanofluid. The present study has been done with a range of nanosized particles 0–4% by volume, and the variation of Reynolds number is kept under the laminar condition. The physical model covers two concentric tubes used to create an annular space. The effects of volume fraction, particle type, and base fluid have been investigated at different Reynolds numbers numerically. Also, the effect of pressure and heat transfer coefficient on the flow behavior of non-Newtonian nanofluids is analyzed. The results concluded that Al 2 O 3 particles showed 219% and CuO particles give 195% higher heat transfer coefficient as compared with pure water.

Thermal Response of Dielectric Nanoparticle Infused Tissue Phantoms during Microwave Assisted Hyperthermia treatment. In this paper, an experimental investigation of microwave assisted thermal heating (MWATH) of tissue phantom using a domestic microwave oven has been reported. Computer simulations using finite element method based tools was also carried out to support the experimental observations and probe insight on the thermal transport aspects deep within the tissue phantom. A good agreement between predicted and measured temperature were achieved. Furthermore, experiments were conducted to investigate the efficacy of dielectric nanoparticles viz. alumina (Al 2 O 3 ) and titanium oxide (TiO 2 ) during the MWATH of nanoparticle infused tumor phantoms. A deep seated tumor injected with nanoparticle solution was specifically mimicked in the experiments. Interesting results were obtained in terms of spatiotemporal thermal history of the nanoparticle infused tissue phantoms. An elevation in the temperature distribution was achieved in the vicinity of the targeted zone due to the presence of nanoparticles, and the spatial distribution of temperature was grossly morphed. We conclusively show, using experiments and simulations that unlike other nanoparticle mediated hyperthermia techniques, direct injection of the nanoparticles within the tumor leads to enhanced heat generation in the neighboring healthy tissues. The inhomogeneity of the hyperthermia event is evident from the local occurrence of hot spots and cold spots respectively. The present findings may have far reaching implications as a framework in predicting temperature distributions during MWA.

The authors regret in the published paper referenced above and agree with the discussion by Pantokratoras [1]. In this corrigendum, non-similar mathematical model is developed to describe the mixed convective nanofluid flow over vertical sheet which is stretching at an exponential rate. In the published article referenced above similarity transformations are utilized to convert the governing nonlinear partial differential equations (PDE's) into ordinary differential equations (ODE's). The important physical numbers such as magnetic field, Brownian motion parameter, thermophoresis, Eckert number, ratio of mass transfer Grashof to heat transfer Grashof, buoyancy parameter and Reynolds number appearing in the dimensionless ODE's are still functions of coordinate "x", therefore the problem is non-similar. In this corrigendum, non-similar model is developed by using non-similarity and pseudo-similarity variables. The dimensionless non-similar model is numerically simulated by employing local non-similarity via bvp4c. The graphical results show no change in behavior. The important thermal and mass transport quantities such as Nusselt number and Sherwood number have been computed for the non-similar model and results are compared with the published article.

Experiments were conducted to evaluate the thermal entropy generation, frictional entropy generation, and exergy efficiency of reduced graphene oxide (rGO)–Fe 3 O 4 –TiO 2 hybrid nanofluid flow in a circular tube under laminar flow. The ternary nanoparticles were synthesized using the sol–gel technique and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR). The stable ethylene glycol-based ternary hybrid nanofluid was prepared and its thermophysical properties, heat transfer, friction factor, and pumping power at various values of particle weight concentrations (0.05–0.2%) and Reynolds number (211–2200) were studied experimentally. Nusselt number, heat transfer coefficient, friction factor, and exergy efficiency augment with increasing values of particle loading and Reynolds number. Results show the thermal conductivity and viscosity increase, as compared to the base fluid, by 10.6% and 108.3% at ψ = 0.2% and 60 °C. Similarly, for ψ = 0.2% and Reynolds number of 1548, and in comparison to the base fluid data, the Nusselt number and heat transfer coefficient enhancement are 17.78% and 24.76%, respectively, the thermal entropy generation reduction is 19.85%, and the exergy efficiency enhancement is 6.23%. At Reynolds number of 221.1, the rise in pressure drop, pumping power, and friction factor is 13.65%, 11.33%, and 16%, respectively, for ψ = 0.2% as compared to the base fluid data. The overall thermal performance of the system is enhanced by 14.32%. New equations are developed for the evaluation of the thermophysical properties, Nusselt number, and friction factor.

This paper reports on numerical simulations of passive cooling of an electronic component. The strategy is based on the fusion of a nano-enhanced phase change material (NePCM) by insertion of hybrid Cu-Al 2 O 3 nanoparticles. This study analyzes the combined effects of the position of the electronic component and the inclination of the heat sink for rectangular and square geometries on the heat transfer and flow structure of liquid NePCM. The heat sink is heated by a protuberant heat source simulating the role of an electronic component generating a volumetric power. The electronic component is mounted on a substrate modeling the role of a motherboard. The development of a 2D mathematical model is based on the equations of conservation of mass, momentum, and energy. This system of equations is solved using the finite volume method and the SIMPLE algorithm for velocity–pressure coupling. The enthalpy-porosity approach is adopted to model the phase change. The results obtained show that the position of the electronic component and the inclination of the enclosure have important effects on the efficiency of the cooling strategy. The inclination of 90 deg and the position of δ = 0.5 represent the case where the cooling of the electronic component is efficient and operates safely with a minimum temperature difference recorded along it. The electronic component is well cooled in a rectangular heat sink than in a square one.

This study presents a thermal performance comparison of various working fluids operating in a parabolic trough collector. Fluids such as gases (helium, carbon dioxide, and air), liquid sodium, and liquids (pressurized water, Therminol VP1, and Syltherm 800) are evaluated. This study also examines the efficiency enhancement obtained from the dispersion of copper nanoparticles in water, Therminol VP1, and Syltherm 800 base fluids. The optimum parameters for nanoparticle concentration, volume flowrate, and inlet temperature to obtain the maximum efficiencies for each working fluid were evaluated in this study. The thermal model used in this study was modeled after the commercially available LS-2 collector, which is designed in the engineering equation solver (EES) and validated with results found in the literature. The results of the study show that the Cu/Syltherm 800 nanofluid showed the most enhancement in thermal efficiency with 0.141%, while Cu/water and Cu/Therminol VP1 had enhancements of 0.037% and 0.088% respectively.

Three-dimensional numerical study is presented in this work that deals with thermo-hydrodynamic and entropy generation analysis of water-based nanofluids in recharging microchannel (RMC). Four different water-based nanofluids (Al 2 O 3 , CuO, SiO 2 , and ZnO) are considered with volume concentrations of 1–5% and nanoparticle diameters of 10–50 nm to understand their effect on thermo-hydrodynamic performance and entropy generation. Substrate bottom surface is subjected to a constant wall heat flux of 100 W/cm 2 while coolant with Reynolds number range of 100–500 flows through the RMC. It is revealed that among all the nanofluids under investigation, water/Al 2 O 3 provides enhanced thermal performance with higher effectiveness parameter (η), and it also shows reduced entropy generation. With increasing volume concentration of water/Al 2 O 3 nanofluid, heat transfer coefficient increases, effectiveness parameter increases, and entropy generation reduces. Water/Al 2 O 3 nanofluid with smaller nanoparticle diameter shows enhanced heat transfer coefficient and reduced entropy generation, whereas it shows decreased effectiveness parameter. This is attributed to increased pressure drop with decreasing particle diameter. This study suggests that an optimized combination of particle diameter and volume concentration should be chosen for using nanofluid-based coolants for high heat flux removal.

Steady-state and transient behaviors of single-phase natural circulation loop (SPNCL) are investigated using four thermal oils (Therminol VP1, Paratherm CR, Dowtherm A, and Dowtherm Q) and water-based ternary hybrid (various combinations of different nature and shaped nanoparticles: Al 2 O 3 , Cu, carbon nanotube (CNT) and graphene) nanofluids as loop fluid. The influences of nanoparticle volume concentration and loop height-to-width ratio on the mass flow rate and total entropy generation rate of SPNCL are investigated. Results disclose that ternary hybrid nanofluids enhance flow initiation, reduce fluctuation and are expected to attain a steady-state faster than water. Steady-state mass flow rate increases/decreases for ternary hybrid nanofluid depending on the shape of the nanoparticle, and the total entropy generation rate decreases as compared to water. Thermal oil shows a higher mass flow rate and total entropy generation rate as compared to water. Al 2 O 3 –Cu–CNT–water and Paratherm CR show the best result among all ternary hybrid nanofluids and thermal oils, respectively. The nanoparticle shape decides the optimum nanoparticle volume fraction. Increasing the height-to-width ratio decreases the total entropy generation and upsurges the mass flow rate at specified input power. The optimum height-to-width ratio depends on the loop fluid.

This work assesses the thermal performance of gold nanofluid as a cooling liquid in a shell and helically coiled tube (SHCT) heat exchanger (HE) built at the bench scale. Tests planned under a multi-level factorial experimental design were carried out to evaluate the effects of the volumetric fraction of the gold nanoparticles, the volumetric flowrate of the working fluid, and the inlet temperature of the hot fluid (water) on the SHCT heat exchanger effectiveness. Spherical gold nanoparticles with a mean diameter of 14 ± 2 nm were produced using Turkevich’s method to be used at two concentrations of approximately 10 −5 vol%. The heat transfer tests were performed at volumetric flowrates of 20, 30, and 40 l/h for both working fluids using heated water at inlet temperatures of 40, 50, and 60 °C. Results showed that the less concentrated nanofluids were comparatively more efficient, suggesting the presence of a range of gold concentration values for improving the heat transfer effectiveness.

The flow of alumina–water nanofluid across heated circular tubes arranged in inline and staggered arrays in a heat exchanger has been studied numerically using the finite volume method (FVM). For calculating the nanofluid’s thermophysical properties such as effective thermal conductivity and effective viscosity, Corcione’s correlations are utilized. Corcione’s correlations consider nanoparticles size, their Brownian motion, and operating temperature while calculating these effective properties of nanofluids. The impact of three parameters on heat transfer characteristics across inline and staggered arrays of heated circular cylinders has been examined. These parameters are nanoparticle diameter d p , which is varied between 10 nm and 50 nm, nanoparticle volume fraction ɸ varying from 0.01 to 0.05, and Reynolds number Re ranging from 10 to 200. It is observed that heat transfer augmentation across both inline and staggered arrays occurs when nanoparticle concentration is increased and smaller diameter nanoparticles are used. Mean Nusselt number Nu M is increased by 31% when ɸ is increased from 0.01 to 0.05 at Re = 200 and d p = 10 nm in an inline array and by 25% in a staggered array. Nu M is enhanced by 20% for the inline array and 16% for the staggering array when d p decreases from 50 nm to 10 nm at Re = 200 and ɸ = 0.05. At any given value of d p , ɸ, and Re, the mean Nusselt number is always higher for staggered array in comparison with the inline array. The results reported in the present study can be utilized for the optimal design of various heat exchange systems under the given operating conditions. The present results are extensively validated with the available experimental/numerical studies.

This study is concerned with studying the performance of SiO 2 –water nanofluid flow through a three-dimensional straight mini-channel with different values of aspect ratio (AR) of (0.5, 1.0, and 1.6) and a fixed hydraulic diameter under a uniform heat flux. The governing equations are developed and solved numerically using the finite volume method for a single-phase flow with standard Kappa-Epsilon ( ҡ –ɛ) turbulence model via a user-defined function (UDF) over the Reynolds number (Re) range of (10,000–35,000). Numerical results indicated that the average Nusselt number ratio increases as the Reynolds number and volume concentration of the nanoparticles increase for all values of the channel aspect ratio. The results indicated that the maximum enhancement of the heat transfer coefficient (benefit) achieved is 94.69% at AR = 0.5, along with the lowest increase of pressure drop (penalty) of 13.1%. The highest performance evaluation criterion (PEC) of 1.64 is found at AR = 0.5, Re = 35,000, and 5% concentration.

The thermal performance analysis of a radiator with a dissimilar shape nanoparticles, i.e., cylindrical (CNT)–platelet (graphene), spherical (Al 2 O 3 )–platelet (graphene), and spherical (Al 2 O 3 )–cylindrical (CNT) composition-based hybrid nanofluid for a coolant flowrate of 6 l/min, air velocity of 10.6 m/s, and 1.3% vol. faction of nanofluid has been studied and compared. Results revealed that a hybrid nanofluid as a coolant enhances the exergy–energy performance of the radiator. In this study, the cylindrical (CNT)–platelet (graphene) hybrid nanofluid results a decrement in the performance while the spherical (Al 2 O 3 )–platelet (graphene) hybrid nanofluid yields a better performance with coolant flowrate and air velocity. Particle shape has influenced a significant effect on the second law efficiency, exergy change, and irreversibility, which increases with an increase in air velocity, and volume fraction of hybrid nanofluid. However, the spherical (Al 2 O 3 )–platelet (graphene) hybrid nanofluid has 3.5%, 3.6%, and 1.12% higher performance index, exergy change in coolant, and second law efficiency, respectively, compared to the cylindrical (CNT)-platelet(graphene)-based hybrid nanofluid. Furthermore, results divulge that the nanoparticle shape has a notable impact on the performance of an automobile radiator. The spherical (Al 2 O 3 )–platelet (graphene) hybrid nanofluid exhibits supercilious over other shapes considered, and hence, it is more effective to use as a radiator coolant for enhancing the thermal performance.

This study used numerical analysis to investigate the effects of nonlinear radiation and variable viscosity on free convection of a power-law nanofluid over a vertical truncated cone in porous media with Rosseland diffusion approximation considering zero nanoparticles flux and internal heat generation. The internal heat generation is of an exponential decaying form and the viscosity of the fluid is assumed to follow Reynolds viscosity model. The surface boundary conditions of vertical truncated cone is maintained at the uniform wall temperature (UWT) and the zero nanoparticle flux (ZNF) to cause the results to be more realistic and useful. The nanofluid model considered the effects of Brownian motion and thermophoresis. The nonsimilar governing equations are obtained by using a suitable coordinate transformation and then solved by Keller box method (KBM). Comparisons with previously published work obtained good agreement. Graphical and tabular presentations of numerical data for the dimensionless temperature profile and the local Nusselt number were presented for main parameters: dimensionless streamwise coordinate, thermophoresis parameter, Lewis number, radiation parameter, surface temperature parameter, viscosity parameter, power-law index of the non-Newtonian fluid, and internal heat generation coefficient. The local Nusselt number increased when the following parameters were increased: radiation parameter, surface temperature parameter, viscosity parameter, power-law index of the non-Newtonian fluid, and dimensionless streamwise coordinate. In contrast, the local Nusselt number decreased when the following parameters were increased: internal heat generation coefficient, thermophoresis parameter, and Lewis number. Besides, the physical aspects of the problem are discussed in details.

The present investigation deals with the flow dynamics and heat transport of the nanofluid flow over a rotating disk. The flow is considered to be laminar and steady. Active–passive controls of tiny nanoparticles influenced by the Brownian motion and thermophoretic migration are included to reveal the variations in the hydrothermal behaviour. Thermal radiation, velocity slip, and thermal slip are also introduced to model the flow. The foremost governing equations are converted into its dimensionless form after applying the requisite similarity transformation. The spectral quasi-linearization method (SQLM) has been employed to extract the numeric outcomes of the flow. Effects of the underlying parameters on the flow and heat-mass transport are revealed through graphs and tables. Several three-dimensional (3D) and streamlines plots are depicted to enrich the Result and Discussion section. Results assured that the velocities in every direction reduce for velocity slip parameter and magnetic parameter. Temperature increases for thermophoresis and Brownian motion, but reduces for velocity and thermal slip parameter. Active flow reveals high temperature than passive flow. The Brownian motion and thermophoresis provide dual scenario for concentration profile. Heat and mass transport always sustain high magnitude for passive flow.

Comparative analysis of the thermal and hydraulic performance of three-fluid tubular heat exchanger has been carried out numerically. Single-phase and multi-phase approaches for the turbulent flow of CuO–water nanofluids have been applied. The effect of Reynolds number (2500–10,000) and volume concentration of nanoparticles (0–3%) on the overall performance of the selected heat exchanger has been investigated. The numerical simulation has been performed using a finite volume approach in commercial computational fluid dynamics (CFD) software for two flow arrangements (parallel and counter). Nusselt number was found to increase with the growth in Reynolds number as well as volume concentration of nanoparticles in both the flow arrangements. Particularly, for a maximum volume concentration of nanoparticles (φ = 3%), single-phase approach resulted in an increase of 8.94% for parallel and 11.52% for counterflow arrangements. However, multi-phase approach produced a remarkable increase of 30.37% for parallel and 32.04% for counterflow arrangement. Single-phase approach was applied for treating the nanofluids as homogenous fluids with effective thermophysical properties, meaning that the entire suspension is assumed to act as a single unit with the same velocity. However, the multi-phase model was applied to separately treat the two phases with different velocities.

In this study, the impact of thermal radiation and partial slip on magnetohydrodynamic flow of the Jeffrey nanofluid comprising motile gyrotactic microorganisms via vertical stretching surface is analyzed. The governing partial differential equations are reformed to a system of coupled ordinary differential equations by utilizing the similarity transformations. The transformed equations are of order four, which are complex to solve analytically and hence, the coupled system is solved computationally by using the shooting technique along the Runge–Kutta integrated scheme. The ramifications of different thermophysical parameters on the density of gyrotactic microorganisms, Jeffrey nanofluid velocity, nanoparticles concentration, temperature, Sherwood number, and Nusselt number are illustrated graphically. Comparing this study with the results already published favors the validity of this study. It is established that the Nusselt number is boosted on enhancing the thermal radiation parameter, and the reverse trend has been observed on increasing the Richardson number, whereas the gyrotactic microorganisms density is more in case of viscous nanofluid compared to the Jeffrey nanofluid.

The present study reports an experimental evaluation of thermal conductivity of Al 2 O 3 /pure coconut oil nano fluids with solid volume fraction varying from 0.1% to 1.2% at a temperature ranging from 303 K to 413 K, respectively. Additionally, the thermophysical properties such as thermal diffusivity, density, and specific heat were also measured. The effect of solid volume fraction and temperature on thermophysical properties of nano fluids was examined. The results confirmed that the thermal conductivity of nano fluids was higher than that of the base fluid with an increase in the solid volume fraction and temperature. Apart from this, the efficiency of nano fluids for the heat transfer application has been evaluated for optimization based on different figures of merit. Further, the experimental thermal conductivity data were compared with different existing models and correlations as the thermal conductivity enhancement of the nano fluid is directly or indirectly a function of almost all thermophysical properties. Hence, a novel dimensionless correlation was developed for predicting the thermal conductivity of pure coconut oil/Al 2 O 3 nano fluids in terms of almost all the thermophysical parameters calculated from the experimental data.

Fabrication of micro- and nanoscale electronic components has become increasingly demanding due to device and interconnect scaling combined with advanced packaging and assembly for electronic, aerospace, and medical applications. Recent advances in additive manufacturing have made it possible to fabricate microscale, 3D interconnect structures but heat transfer during the fabrication process is one of the most important phenomena influencing the reliable manufacturing of these interconnect structures. In this study, optical absorption and scattering by three-dimensional (3D) nanoparticle packings are investigated to gain insight into micro/nano heat transport within the nanoparticles. Because drying of colloidal solutions creates different configurations of nanoparticles, the plasmonic coupling in three different copper nanoparticle packing configurations was investigated: simple cubic (SC), face-centered cubic (FCC), and hexagonal close packing (HCP). Single-scatter albedo (ω) was analyzed as a function of nanoparticle size, packing density, and configuration to assess effect for thermo-optical properties and plasmonic coupling of the Cu nanoparticles within the nanoparticle packings. This analysis provides insight into plasmonically enhanced absorption in copper nanoparticle particles and its consequences for laser heating of nanoparticle assemblies.

Two Semi-Implicit-Method for Pressure-Linked-Equations (SIMPLE) techniques have been performed to solve the dimensionless equations governing a dusty hybrid nanofluid flow in wavy enclosures contain a volumetric heat source. These techniques are applied to evaluate the pressure terms for both the hybrid nanofluid and the dusty particles based on the control volume solver. Two systems of equations are proposed to simulate the hybrid nanofluid phase and the dusty particles phase. In addition, a body-fitted method is applied to map the irregular domain into a rectangular domain, and an inverse map technique is used to present the obtained data inside the given wavy domain. The hybrid mixture, here, is consisting of water as a base fluid, and the nanoparticles are Al 2 O 3 and Cu. The controlling parameters are the Rayleigh numbers Ra E and Ra l , the ratio of the densities of the mixture D s , the dusty parameter α s , and the total nanoparticles volume fraction. The results revealed that the absolute values of the stream function are reduced by 54.5% when the heating modes are switched from (Ra l /Ra E ) < 1 to (Ra l /Ra E ) > 1. Also, the average Nusselt is enhanced by 5.2% at a = 0.9, 6.74% at a = 0.95, and 11.36% at a = 1.1 when the nanoparticles volume fraction is increased from 1% to 5%.