Heat Transfer Enhancement Of Nanofluids Research Articles

Heat transfer enhancement of nanofluids in concentric cylindrical heat exchanger

Two models of heat transfer channels for concentric cylindrical heat exchangers with porous ribs are developed herein to optimize the transfer efficiency of the heat storage reactor channels. Rings and spiral ribs are added to the smooth circular tube inside the reactor. Spoiler holes are arranged in the ribs to reduce the stagnation area around the ribs. The effects of coolant (SiO2–H2O nanofluids), rib shapes, and the number of holes in the rib on the overall performance of the heat storage system were numerically investigated. Results revealed that the 0.5% mass fraction nanofluids are the most suitable working fluid for channel thermal transport in the simulated Reynolds number range. Both ring ribs and spiral ribs reinforce the heat exchange of the pipe to varying degrees. Spiral perforated ribs have superior heat transfer and drag reduction performance compared with ring ribs. The comprehensive performances of spiral ribs are always higher than those of ring ribs under all conditions.

Microfluidic controllable production and morphology-independent phase-change heat transfer of boehmite nanofluids

Enhanced boiling heat transfer through nanofluids represents a significant approach to improving the cooling performance of electronic devices. However, the preparation of nanofluids poses challenges regarding production efficiency, morphology control, and structural stability. In addition, the underlying mechanism of flow boiling heat transfer enhancement of nanofluids, particularly changes in vapor behavior, remains a limited understanding. This study presents a facile and straightforward microfluidic strategy for the controllable synthesis of nanofluids toward efficient heat transfer enhancement. The microfluidic flow synthesis approach effectively enhances mixing efficiency at various flow rates, enabling continuous and high-throughput synthesis of boehmite nanofluids with different morphologies. The synthesized nanofluids exhibit long-term stability (>50 days) at room temperature. Both rod- and sphere-shaped nanofluids under equivalent concentrations can significantly improve critical heat flux (CHF) and maximum heat transfer coefficient (HTC) across various operating parameters, but with similar enhancement characteristics. Analysis of the period of bubble growth and burst, bubble size distributions, number of bubbles, and vapor phase fractions reveals that rod- and sphere-shaped nanofluids could shorten the period, enhance surface wetting, increase nucleation sites, and reduce bubble size efficiently and similarly. Furthermore, the effect of the concentration of nanofluid on phase-change heat transfer performance is systematically explored. 0.01 wt% nanofluid behaves the most remarkable enhancement, CHF and maximum HTC are improved by 24 % and 14.4 %, respectively. These findings not only shed new light on the controllable synthesis of functional nanomaterials but also provide important guidelines for the rational design of nanofluids for efficient two-phase cooling of electronic devices.

Heat transfer enhancement of nanofluids in a four-blade LPD static mixer

The heat transfer performance of nanofluids within a four-bladed LPD static mixer was investigated using a combination of experiments and simulations under constant heat flow boundary conditions with Re ranging from 3519 to 16719. Al2O3-H2O nanofluid with volume fraction φ = 0.3 % was prepared experimentally and the stability of the nanofluid was analyzed by settling observation method and Dynamic light scattering (DLS). Numerical simulations were adopted to analyze the effects of nanoparticle types, volume fractions and types of mixing nanofluids on the heat transfer enhancement inside the four-bladed LPD static mixer. The results show that the maximum error of Nusselt number (Nu) between the predicted values of Mixture model and experimental values was 7.39 %. Because of the combined heat transfer performance coefficient PEC more than 1 with the increasing of Re, the mixers with α = 30° and β = 45° instead of KSM could be recommended when Re > 5279. The PEC of Al2O3-H2O nanofluids gradually increases with the increasing φ. At the same Re and φ, the flied synergy number Fc and PEC of the mixed nanofluids are 1.01–1.47 times and 1.15–3.35 times higher than those of the single nanofluids.

Comparative analysis of CFD and ANFIS for predicting heat transfer enhancement in water-Fe2O3 nanofluids across various flow regions

Models for enhancement of heat transfer in nanofluids made wide use of adaptive neural fuzzy inference system (ANFIS) and the multi-phase mixture model in recent years. These models originate from two separate but complementary branches of engineering: computational mechanics and machine intelligence. Not only have prior studies used only a small subset of nanofluid and flow parameters in their analyses, but no one has ever compared the two methods to determine which one is more applicable to certain flow regimes to forecast how much heat transfer development nanofluids will exhibit. The purpose of this study was to compare the accuracy of two methods ? CFD and ANFIS in predicting the heat transfer improvement of water-Fe2O3 nanofluid for variety of nanofluid formations and flow characteristics, and recommend the method that would be most useful in predicting this enhancement for each flow regime. While ANFIS consistently outperforms the mixture models in prediction of nanofluid heat transfer enhancement, the latter can sometimes produce results that differ greatly from experimental correlation; however, for nanofluid configurations, the mixture model?s predictions can be dependable (with 1% error).

Numeričko ispitivanje prenosa toplote prirodnom konvekcijom korišćenjem nanofluida TiO₂/Al₂O₃-voda

Recently, nanofluids have been used as an alternative in several industries to improve the heat transfer process. This paper focuses on the numerical modeling of the performance of the natural convection process through TiO₂/Al₂O₃-water nanofluids in a square cavity containing a heated block. The lattice Boltzmann method is used in this study to present the nanofluid heat transfer enhancement. Results are presented in terms of streamlines, isothermal contours, and Nusselt number profiles. The findings demonstrate that by raising the Rayleigh number and solid nanoparticle concentration, the average Nusselt number increases, and they reveal that the heated block enormously affects the flow structure and heat transfer. It is also demonstrated that the type of nanoparticles significantly impacts the natural convection heat transfer.

Theoretical Examination of the Volume Concentration and Nanoparticles Density Influence on the Convective Heat Transfer Enhancement of Nanofluid in 2D Cavity Including the Square Heater

Nanofluid is one of the solutions of heat transfer, which can apply in devices fields as nuclear power, Nano-electronics systems, and solar fluid heating. In this work, the natural convection of Cuwater nanofluid is examined using the Lattice Boltzmann Method (LBM) as a mesoscopic approach. The main objectives of this work are to study the performance and pattern of Cu-water nanofluid and to demonstrate that the nanofluids behave differently while improving their energy transfer compared to pure fluids. The set goal was achieved by solving the tasks: based on the streamlines and isotherms profiles to demonstrate how the convection process and temperature gradients improve. Also, conducting study on heat transfer of nanofluid by calculate the Nusselt number. Depending on the nanoparticle volume percentage, the Grashof number Gr , and the hot obstacle have a significant impact on the convection flow and rate of heat transfer. The most important result is the enhancement of heat transfer with the increasing of volume fraction for a particular Grashof number, also it improves with the rising of Grashof number for a particular nanoparticles volume fraction. Therefore, the aspect ratios of the enclosure have played a significant part in Nusselt number variation. In addition, we found that the Nusselt number avg Nu is higher in the case of cavity without hot obstacle more than for cavity with hot obstacle, so the heat transfer improves in the case of cavity without hot obstacle. The significance of the obtained results consists that the nanofluid is one of the ways to improve heat transfer due to its specific characteristics and properties.

Friction Factor and Heat Transfer Enhancement of Hybrid Nanofluids in a Heated Circular Tube

Friction Factor and Heat Transfer Enhancement of Hybrid Nanofluids in a Heated Circular Tube

Time-dependent analysis of heat transfer enhancement and entropy generation of hybrid nanofluids in a tube with a solid and elliptical‑cut twisted tape insert with non-uniform heat flux

ABSTRACT This numerical study investigates the improvement of transient heat transfer in a plain tube using hybrid nanofluids consisting of solid particles and twisted tapes with elliptical cuts, under non-uniform heat flux conditions. The analysis includes the calculation of the Bejan number and entropy production. Different working fluids, including water, CuO/water nanofluid, and a hybrid nanofluid with a 2% volume concentration of Al2O3-Cu/water, are used with varying concentrations of the hybrid nanofluid ranging from 1% to 4%. Effects of heat flux distribution and local concentration ratio (LCR) are investigated. The computational results indicate that conventional and elliptical cut twisted tapes enhance transient heat transmission. A slight rise in the heat transfer coefficient is observed when the fluid has higher thermal conductivity. The flow velocity gradually stabilizes over time. The hybrid nanofluid of (Al2O3-Cu/water) significantly affects transient heat transmission, reducing the maximum temperature difference by approximately 4.1% compared to water and 6.2% compared to the nanofluid. Transient heat transmission is further intensified by TECT. Moreover, frictional entropy production dominates the system’s irreversibility. This study contributes to the understanding of transient heat transfer enhancement and its dependence on hybrid nanofluids, providing insights for engineering applications.

Secondary vortex drag reduction and heat transfer enhancement of nanofluids in hierarchical microchannels applied to thermal management of electronic components

In order to improve the heat dissipation performance of electronic components, two hierarchical microchannel structures with curve and straight corners are proposed, and semi-circular and trapezoidal secondary flow structures are introduced into the structure with the best performance. The effects of coolant (Fe3O4-water nanofluid), layered structure and secondary flow structure on the comprehensive performance of MCHS were studied by numerical simulation. Results showed that deionized water is more suitable for the heat dissipation of microchannels at this scale. The hierarchical structure has the effect of enhancing heat transfer, and Nu can be increased by up to 67.32 %. The introduction of secondary flow structure has drag reduction effect in a certain Reynolds number range. The hierarchical MCHS with semi-circular secondary flow structure has drag reduction effect in the Reynolds number range of Re = 200–400, and the pressure drop can be reduced by up to 1.89 %. The hierarchical MCHS with trapezoidal secondary flow structure always has a drag reduction effect in the range of Reynolds number Re = 200–600, and the maximum pressure drop can be reduced by 2.46 %, showing excellent drag reduction ability. In addition, the introduction of trapezoidal secondary flow in MCHS increases the Nusselt number by 9.70 %, the comprehensive performance index reaches 1.10, and the cooling performance and comprehensive performance are optimal. The combination of hierarchical structure and secondary flow structure has excellent drag reduction and heat transfer enhancement effects, and has broad application prospects in the field of thermal management of electronic devices.

Localized magnetic fields and their effects on heat transfer enhancement and vortices generation in tri-hybrid nanofluids: A novel investigation

A localized magnetic field is a vector field that alters in space because of magnetic materials or electric currents. Some examples of localized magnetic fields are indoor localization, magnetic anomaly detection, magnetoencephalography, and quantum physics. Magnetic fields can be used to estimate the orientation and position of a device inside a building by measuring the changes in the magnetic field caused by ferromagnetic substances. On the other hand, a Tri-hybrid nanofluid can transfer heat better than a normal hybrid nanofluid by mixing three different nanoparticles with synergistic effects. It can have more varied physical and thermal properties by choosing different combinations of nanoparticles. That's why it has more possible uses in various fields such as solar thermal, biomedical, and industrial processes. Therefore, the goal of this research is to explore the complex dynamics of the localized magnetized force that affects the rotation of nanostructures and the vortex formation in the tri-hybrid nanofluid flow regime using the single-phase model, while the governing partial differential equations are discretized numerically. With the help of our self-developed computer codes in MATLAB language, we intend to understand the way these parameters affect the flow and thermal properties of the nanofluids. Additionally, the current work provides a novel analysis that makes it possible to investigate the flow lines and isotherms associated with the magnetic strips inside a flow field. It is discovered that the spinning of tri-hybrid nano-particles, which creates the intricate structure of vortices inside the flow regime, results from the magnetized field. Further, the investigations reveal that both the local skin friction (CfRe) and the Nusselt number (Nu) increased by up to 46% and 99% when the magnetic field is strengthened. Finally, adding more nanosized particles in the flow field result in increased both Nu and CfRe, but differently for different nanoparticles. Silver (Ag) had the highest increase in both Nu (55%) and CfRe (110%), showing strong thermal-fluid coupling. Alumina Al2O3 and Titanium Dioxide (TiO2) had lower increases in both Nu (33% and 25%) and CfRe (13% and 9%), showing weaker coupling in the flow regime.

Numerical Investigation of Heat Transfer Enhancement of Al2O3 Nanofluid in Microchannel Heat Sink

This study focusses on using computational fluid dynamics (CFD) to study the enhancement of heat transfer from the use of AL2O3 nanofluid in a microchannel heat sink (MCHS) to develop a more efficient cooling device for high-power integrated circuits. The objective is to investigate the heat transfer performance, parameters, and enhancement rate using Ansys Fluent software, and to compare the results with experiments to show the effectiveness of this method. This study will also focus on the relationship between the friction fraction and nanoparticles volume fraction to improve the heat transfer enhancement in the MCHS. The temperature, pressure, heat transfer coefficient, Nusselt number, and friction coefficient are analysed in this study. The results showed that an increase in the volume fraction of the nanofluid leads to an increase in the average heat transfer coefficient. The results showed that for 4% nanofluid volume concentration, the Nusselt Number has improved by 10% compared to pure water. However, an increase in volume concentration also resulted in an increase in pressure drop.

Comment on “Investigation of heat transfer enhancement of Cu-water nanofluid by different configurations of double rotating cylinders in a vented cavity with different inlet and outlet ports” [International Communications in Heat and Mass Transfer, 126 (2021) 105432]

The following comments address a few missing information that resulted in inaccurate qualitative and quantitative findings in the aforementioned article. This analysis, therefore, serves as a comparison and correction to the publication “Investigation of heat transfer enhancement of Cu-water nanofluid by different configurations of double rotating cylinders in a vented cavity with different inlet and outlet ports” by H. Moayedi, Int. Comm. Heat Mass Transfer 126 (2021) 105432.

Numerical Investigation of Heat Transfer Enhancement of Nanofluids with Rod-Like Particles in Micro Pin Fin Heat Sink Channel

Numerical Investigation of Heat Transfer Enhancement of Nanofluids with Rod-Like Particles in Micro Pin Fin Heat Sink Channel

Turbulent natural convection heat transfer enhancement of nanofluids

This study investigates the enhancement of heat transfer for the fluid with the addition of nano-particles in a two-dimensional rectangular cavity. Thermo-physical properties of such fluids and volume fraction of nano-particles in those fluids and its heat transfer characteristics are studied. ANSYS Fluent code is utilized for this purpose. Validation of the computational model has been carried out against the benchmark data available from the literature. A heat transfer correlation in terms of the Nusselt number (Nu) average as a function of Grashoff number and volume fraction of the nano-particles in the base fluid for the turbulent flow is developed and formulated in this study.

A Study on Accuracy Range of Multiphase Mixture Model for Turbulent Convective Heat Transfer Enhancement Simulation of Water-Al2O3 Nanofluid

Because of complications and cost of experimental studies, simulating heat transfer of nanofluids using the methods of computational fluid dynamics (CFD) has become a reliable approach to work with them. As Mixture model remains as one of the most heavily used CFD models to examine the heat transfer enhancement of nanofluids according to literature, finding out the range of nanofluid configurations for which the Mixture model is able to provide satisfactory results is a necessity. In this study, turbulent flow of water-Al2O3 inside a circular pipe under uniform wall temperature has been simulated in order to find out the conditions for Mixture model to yield reliable results in terms of predicting heat transfer enhancement of nanofluids. Along with depicting significant increase in heat transfer with particle concentration hike, the results suggested that Mixture model predicts heat transfer enhancement the most accurately for nanoparticle concentration of around 3% with an average discrepancy of less than 1% from experimental data, though the results for particle concentration range of 2.5% to 3.5% are quite satisfactory yielding average error lower than 8%.

Effect of Wall Electrical Conductivity on Heat Transfer Enhancement of Swirling Nanofluid-Flow

Effects of electrical conductivity of cylindrical walls on both heat transfer enhancement in nanofluid swirling flow and fluid layers produced in a cylindrical container are numerically analyzed. A temperature gradient and external magnetic field are imposed in the axial direction on the rotating flow which is moved by the bottom disk. The governing equations that describe the combined problem (MHD and mixed convection) under the adoptive assumptions are solved numerically by the finite volume technique. Calculations were made for fixed Reynolds number (Re = 1000), Richardson number (0 ≤ Ri ≤ 2), aspect ratio (H/R = 2), Hartmann number (0 ≤ Ha ≤ 60), and solid nanoparticle (copper) with volume fraction (Φ = 0.1). A decrease in the mean Nusselt number was found with the increase of the Richardson number due to stratification layers. These latter limits the heat transfers between the hot and cold zones of the cylinder. The results indicate that the Nusselt number gets bigger within a certain range of Hartmann numbers, and especially when the rotating lid is electrically conducting. Indeed, average Nusselt number decreases while the Hartmann number increase after it exceeds a critical value. Finally, the electrical conductivity of the rotating lid plays an important role in heat transfer enhancement in nanofluid swirling flow.

Thermal performance investigation of LiBr solution–based nanofluids in plate heat exchangers

ABSTRACT The poor heat transfer performance of LiBr solution is one of the main obstacles to improving the performance of absorption cooling systems. In this study, the combined effects of the heat transfer enhancement and pressure loss increment of LiBr solution-based nanofluids in plate heat exchangers are investigated theoretically. First, a correlation for predicting the Nusselt number of the LiBr solution in a chevron plate heat exchanger with different chevron angles is developed based on the experimental data, and the prediction error is in the range of−3.8% to 6.0%. Second, the heat transfer coefficients and friction factors of Al2O3 nanofluid and MWCNT nanofluid are numerically calculated. The nanofluids have higher heat transfer rates than the LiBr solution. The heat transfer enhancement of the nanofluid in the 30°Chevron type plate heat exchanger is similar to that in the 60°Chevron type plate heat exchanger. The Nusselt number and heat transfer coefficient of the Al2O3 nanofluid with a 2.5% volume fraction are about 2.2% and 9% higher than those of the LiBr solution. The Nusselt number and heat transfer coefficient of the MWCNT nanofluid with 0.05% volume fraction are about 7.8% and 8.1% higher than those of the LiBr solution. The friction factor increases with the rising nanofluid volume fraction because the viscosity increases. When the nanofluid volume fractions are one-third and two-thirds of the equivalent value, the performance coefficient improvement of MWCNT nanofluid is about two to four times higher than that of the Al2O3 nanofluid. When the volume fraction is one-third of the equivalent value, the performance coefficient improvement of Al2O3 is about 30% to 40% higher than that of the MWCNT nanofluid. When the volume fraction of MWCNT nanofluid is between 0.01% vol. and 0.02% vol. and that of Al2O3 nanofluid is between 1% vol. and 1.5% vol. the heat transfer performance and economic performance of the two nanofluids can be regarded as equivalent. Finally, the appropriate selections of LiBr-solution based nanofluids for different application requirements are presented.

Study on heat transfer enhancement of nanofluid in a new type of heat exchangers

As one of the essential equipment in industrial production, improving the efficiency of heat exchangers to slow down energy consumption has become a popular topic. In this paper, the structure of a conventional fixed tube plate heat exchanger is optimized by numerical simulation, replacing the straight tube with a wavy wall tube. The impact of particle size of Cu-water nanofluid on the performance in the new heat exchanger (HEX) is also investigated. The results indicate that using the wavy wall tube enhances the flow field perturbation and improves the working mass’s flow state; adding nanoparticles in water can improve the heat transfer capacity of the fluid. It is also found that the shell process pressure drops (ΔP) and the heat transfer effect of the HEX increased with increasing of the fluid volume flow rate; at the same volume flow rate and the volume fraction of 0.5%, the ΔP of the Cu-water nanofluid in the HEX increases with increasing of the particle size. The heat transfer performance decreases gradually with increasing of the particle size. The smaller particle size of Cu nanoparticles can improve the efficiency of enhanced heat transfer to a larger extent.

Influences of electrical conductivity of the cylindrical walls on heat transfer enhancement of nanofluid swirling flow

The swirling nanofluid flow driven by a revolving bottom disk of a cylindrical container under magnetic field effect and temperature gradient is examined in this study. The effects of the electrical conductivity of cylindrical walls’ on heat transfer enhancement are quantitatively investigated. The finite volume approach is used to solve the governing equations under the appropriate assumptions. This study considers four cases of combined electric conducting and insulating walls. The solid nanoparticle (copper) with volume fraction (ϕ = 0.1) is added to water. Calculations were done for fixed Reynolds number (Re=1000), Richardson number (0≤Ri ≤2), and various Hartmann numbers. The mean Nusselt number decreased as the Richardson number increased owing to stratification layers. These latter restrict heat exchanges between the cylinder’s hot and cold zones. The results show that within a particular range of Hartmann numbers, the Nusselt number increases, especially when the revolving lid is electrically conducting. The best heat transfer occurs when all of the walls are electrically conductive, which results in a 100% improvement at low Richardson values. Finally, the electrical conductivity of the revolving lid was a key factor in enhancing heat transfer.

Turbulent convective heat transfer enhancement modeling of water-Al2O3 nanofluid using CFD mixture model and adaptive neural fuzzy inference system

ANFIS and multiphase Mixture model, two different methods from two very distinct engineering domains: Machine Intelligence and Computational Mechanics, have been put into a good amount of use over the past few years for modeling of nanofluids heat transfer enhancement. However, not only the previous investigations using both of these approaches suffer from the use of narrow range of nanofluid and flow properties, but also never have these two particular approaches been juxtaposed to point at a superior approach for specific flow regimes for predicting nanofluids heat transfer enhancement. In this study, water-Al2O3 nanofluid has been simulated using CFD multiphase Mixture model and ANFIS in order to assess the precision of both approaches to predict heat transfer enhancement of water-Al2O3 nanofluid for a very wide range of nanofluid configurations and flow properties, and to suggest the better approach for prediction of heat transfer enhancement for each specific flow regime. The results suggest that almost in every single case ANFIS is able to predict the heat transfer enhancement of nanofluids very efficiently with a maximum error of 0.35%, but the Mixture models’ predictions deviate significantly from the experimental correlation in some cases, though for intermediate nanofluid configurations, yielded results by Mixture model could be reliable with error around 1%.