Heat Transfer Enhancement Of Nanofluids Research Articles

Validity of Performance Factors Used in Recent Studies on Heat Transfer Enhancement of Nanofluids

Abstract Many previous studies used the performance factors for the evaluation of heat transfer enhancement of nanofluids under the identical pumping power. The validity of the performance factors was not examined yet. The validity of the performance factors used in previous studies examined considered only flows in a circular tube based on the empirical correlations and experimental data. It was found that the performance factors used in the previous studies are not valid for the evaluation of heat transfer enhancement of nanofluids. Furthermore, this paper shows that the direct comparison of heat transfer rates without the assumptions of equal surface area and the equal temperature difference is suitable for the evaluation of heat transfer enhancement of single-phase fluids.

Magneto-nanofluid coolants past heated shrinking/stretching surfaces: Dual solutions and stability analysis

Recent advancement in nanotechnology has provides a veritable platform for the emergence of a better ultrahigh-performance coolant known as nanofluid for many engineering and industrial technologies. In this study, we examine the influence of magnetic field on heat transfer enhancement of nanofluids coolants consisting of Cu-water, Al2O3-water, and Fe3O4-water over a slippery but convectively heated shrinking and stretching surfaces. Based on some realistic assumptions, the nonlinear model differential equations are obtained and numerically tackled using shooting procedure with Runge-Kutta-Fehlberg integration scheme. The existence dual solutions in the specific range of shrinking surface parameters is found. Temporal stability analysis to small disturbances is performed on these dual solutions. It is detected that the upper solution branch is stable, substantially realistic with positive smallest eigenvalues while the lower solution branch is unstable with negative smallest eigenvalues. Influence of numerous emerging parameters on the momentum and thermal boundary layer profiles, skin friction, Nusselt number and heat transfer enhancement rate are depicted graphically and quantitatively discussed.

Technology for Optimizing Flue Gas Pollutant Emission Reduction in Oil Field Heating Furnace Combustion

The energy consumption of the heating furnace is an important part of the energy consumption of the oilfield gathering and transportation system. The low energy efficiency of the heating furnace will directly lead to the increase of oilfield production costs. In response to the national energy-saving and emission-reduction policy, the oilfield has implemented energy-saving practices in heating furnace load adjustment, efficient combustion, excess air coefficient control, flue gas waste heat utilization, and furnace modification. It is clear that the energy efficiency of oilfield heating furnaces is still lower than foreign advanced levels. There is an urgent need for further energy conservation and efficiency enhancement. MVR low-temperature flue gas heat recovery technology, flame shape matching technology, nanofluid heat transfer enhancement technology, solar auxiliary heating technology and other new technologies that can be used for energy saving and consumption reduction of oilfield heating furnaces provide a reference for oilfield heating furnaces to tap the potential and increase efficiency.

Heat transfer properties of metal, metal oxides, and carbon water-based nanofluids in the ethanol condensation process

This work investigates the convective heat transfer enhancement of water-based nanofluids in pipe heat exchanger used for the ethanol condensation process. The nanofluids were produced with different nature of nanoparticles, Cu, Fe3O4, MWCNT, and graphene, in the volume concentration 0.01–0.1%, using different surfactants. These nanoparticles are characterized by X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), specific surface area (BET), and Dynamic light scattering (DLS). Density, thermal conductivity, and viscosity of base fluids and nanofluids were experimentally determined at a relevant temperature of 20 °C. Convective heat transfer enhancement under laminar regime was evaluated from a well-designed experimental setup. As the main results, the thermal conductivity of nanofluids increases up to 3–5% and the viscosity can increase or decrease with nanoparticle concentration, showing a lubricating effect of nanoparticles coupled with respective surfactant. It was shown that the heat transfer properties, heat transfer coefficient, and Nusselt number, are increased with nanofluids compared to water and base-fluids, up to 20%, in the range of Pe 2000–10000. Experimental heat transfer properties are shown to be greater than theoretical ones. Finally, copper nanofluid at low concentration appear to be the best candidate for the application and pipe flow geometry considered.

Computational study on heat transfer and MHD‐electrified flow of fractional Maxwell nanofluids suspended with SWCNT and MWCNT

AbstractRecent developments in fluid dynamics have been focusing on nanofluids, which preserve significant thermal conductivity properties and magnify heat transport in fluids. Classical nanofluid studies are generally confined to models described by partial differential equations of an integer order, where the memory effect and hereditary properties of materials are neglected. To overcome these downsides, the present work focuses on studying nanofluids with fractional derivatives formed by differential equations with Caputo time derivatives that provide memory effect on nanofluid characteristics. Further, heat transfer enhancement and boundary layer flow of fractional Maxwell nanofluid with single‐wall and multiple walls carbon nanotubes are investigated. The Maxwell nanofluid saturates the porous medium. Also, buoyancy, magnetic, electric, and heating effects are considered. Governing continuity, momentum, and energy equations involving Caputo time‐fractional derivatives reduced nondimensional forms using suitable dimensionless quantities. Numerical solutions for arising nonlinear problems are developed using finite difference approximation combined with L1 algorithm. The influence of involved physical parameters on flow and heat transfer characteristics is analyzed and depicted graphically. Our simulations found out that surface drag of Maxwell nanofluid with single‐walled carbon nanotubes dominates nanofluids with multiple walls carbon nanotubes, but the reverse trend is noticed for larger Grashof number values.

Two-phase model for mixed convection and flow enhancement of a nanofluid in an inclined channel patterned with heated slip stripes

PurposeThe purpose of this study is to analyze the heat transfer and flow enhancement of an Al2O3-water nanofluid filling an inclined channel whose lower wall is embedded with periodically placed discrete hydrophobic heat sources. Formation of a thin depletion layer of low viscosity over each hydrophobic heated patch leads to the velocity slip and temperature jump condition at the interface of the hydrophobic patch.Design/methodology/approachThe mixed convection of the nanofluid is analysed based on the two-phase non-homogeneous model. The governing equations are solved numerically through a control volume approach. A periodic boundary condition is adopted along the longitudinal direction of the modulated channel. A velocity slip and temperature jump condition are imposed along with the hydrophobic heated stripes. The paper has validated the present non-homogeneous model with existing experimental and numerical results for particular cases. The impact of temperature jump condition and slip velocity on the flow and thermal field of the nanofluid in mixed convection is analysed for a wide range of governing parameters, namely, Reynolds number (50 ≤ Re ≤ 150), Grashof number (), nanoparticle bulk volume fraction (5), nanoparticle diameter () and the angle of inclination ().FindingsThe presence of the thin depletion layer above the heated stripes reduces the heat transfer and augments the volume flow rate. Consideration of the nanofluid as a coolant enhances the rate of heat transfer, as well as the entropy generation and friction factor compared to the clear fluid. However, the rate of increment in heat transfer suppresses by a significant margin of the loss due to enhanced entropy generation and friction factor. Heat transfer performance of the channel diminishes as the channel inclination angle with the horizontal is increased. The paper has also compared the non-homogeneous model with the corresponding homogeneous model. In the non-homogeneous formulation, the nanoparticle distribution is directly affected by the slip conditions by virtue of the no-normal flux of nanoparticles on the slip planes. For this, the slip stripes augment the impact of nanoparticle volume fraction compared to the no-slip case.Originality/valueThis paper finds that the periodically arranged hydrophobic heat sources on the lower wall of the channel create a significant augmentation in the volume flow rate, which may be crucial to augment the transport process in mini- or micro-channels. This type of configuration has not been addressed in the existing literature.

Experimental Study on Thermophysical Properties of Propylene Glycol-Based Graphene Nanofluids

This study determined the optimal dispersion conditions of nanofluids by orthogonal experiments. Stable graphene/propylene glycol nanofluids are successfully prepared by a "two-step method" using a 60 wt % propylene glycol deionized water solution as the base fluid, and its thermal conductivity and viscosity are evaluated. Additionally, the effects of the graphene mass concentration and nanofluid temperature on thermal conductivity and viscosity are expounded, and a model for the prediction of thermophysical properties is established. The combined effect of thermal conductivity and viscosity on the heat transfer enhancement of nanofluids is analyzed theoretically, and the optimum mass concentration of graphene is determined. The results show that the thermal conductivity of nanofluids increases with the increase of the graphene concentration and nanofluid temperature. Also, the viscosity of nanofluid increases with the increase of the graphene concentration and decreases significantly with the increase of the nanofluid temperature. When the mass concentration of graphene is higher than 0.2 wt %, the increase in thermal conductivity caused by the increase of the graphene mass concentration decreases significantly, while the increase of viscosity increases significantly, and the effect of the heat transfer enhancement is almost not improved.

Numerical study of heat transfer enhancement of non-Newtonian nanofluid in porous blocks in a channel partially

This study investigated heat transfer enhancement and pressure drop for forced convection in a parallel channel partially filled with porous blocks and non-Newtonian nanofluid. There are four porous types in the channel are inserted to partially fill the channelthat used non-Newtonian nanofluid. The effect of the Brownian motion term in forced convection on the flow is examined. CuO-Water has been considered as nanoparticles.Simulation is based on two energy equations for solid and fluid regions and Darcy model in the porous blocks and a single-phase model for mixture of nano particle and based fluid. Effects of parameters has been discussed such as index of power law, Reynolds number, thermal conductivity ratio and nano-particle volume fraction. The numerical analysis assumed that the channel is subjected to heat flux in one side. The results showed that Reynolds number increased led to an improvement in heat transfer for 300 to 400 and it can be improve the Nusselt number by 31% for power-law index 1.5 in compared with Newtonian fluid. Heat transfer coefficient is increased by 12.8% for the power low index 1.5 compared with Newtonian fluid with increasing nano particle.

A Review on Thermophysical Properties and Nusselt Number Behavior of Al2O3 Nanofluids in Heat Exchangers

During the last several years, the increase in cooling power requirements for heat exchangers have led to an escalation in heat transfer studies being performed on the use of nanofluids as heat transfer fluids. However, limited effort has been attempted to relate and interpret these findings or the anomalies associated with them. The paper compiles test data from several studies conducted on different types of heat exchangers. In this review, a concentrated effort is spent to clarify the ambiguities regarding the effect of nanoparticle size on the nanofluid thermal conductivity and Nusselt number. Results show that the nanofluid thermal conductivity is not influenced by the nanoparticle size, but by the clustering of the particles themselves. The less compact the structure of the nanoparticle clustering is, the greater the enhancement in the nanofluid thermal conductivity is. Data were also compiled to interpret the relation between the nanofluid flow pattern, nanoparticles volume fraction in the base fluid, and the convective heat transfer. The results from the majority of the heat exchanger studies show an increase in the heat transfer coefficient with the increase in nanoparticle volume fraction. However, studies conducted on plate heat exchanges display some inconsistencies. In the majority of the heat exchanger studies with the exception of few, the decrease in the nanoparticle size is shown to result in an enhancement of the bulk fluid Nusselt number. Compiled test data also reveal that the effectiveness of the alumina nanoparticles is dependent on the flow pattern. The increase in the nanoparticles concentration is shown to result in an increase in the nanofluid heat transfer enhancement as the fluid is transitioning from laminar to turbulent flow. In general, the smaller the nanoparticle size is, the greater the enhancement in the fluid Nusselt number is.

The Impact of Nanofluids on Droplet/Spray Cooling of a Heated Surface: A Critical Review

Cooling by impinging droplets has been the subject of several studies for decades and still is, and, in the last few years, the potential heat transfer enhancement obtained thanks to nanofluids’ use has received increased interest. Indeed, the use of high thermal conductivity fluids, such as nanofluids’, is considered today as a possible way to strongly enhance this heat transfer process. This enhancement is related to several physical mechanisms. It is linked to the nanofluids’ rheology, their degree of stabilization, and how the presence of the nanoparticles impact the droplet/substrate dynamics. Although there are several articles on droplet impact dynamics and nanofluid heat transfer enhancement, there is a lack of review studies that couple these two topics. As such, this review aims to provide an analysis of the available literature dedicated to the dynamics between a single nanofluid droplet and a hot substrate, and the consequent enhancement or reduction of heat transfer. Finally, we also conduct a review of the available publications on nanofluids spray cooling. Although using nanofluids in spray cooling may seem a promising option, the few works present in the literature are not yet conclusive, and the mechanism of enhancement needs to be clarified.

A Review on Heat Transfer of Nanofluids by Applied Electric Field or Magnetic Field.

Nanofluids are considered to be a next-generation heat transfer medium due to their excellent thermal performance. To investigate the effect of electric fields and magnetic fields on heat transfer of nanofluids, this paper analyzes the mechanism of thermal conductivity enhancement of nanofluids, the chaotic convection and the heat transfer enhancement of nanofluids in the presence of an applied electric field or magnetic field through the method of literature review. The studies we searched showed that applied electric field and magnetic field can significantly affect the heat transfer performance of nanofluids, although there are still many different opinions about the effect and mechanism of heat transfer. In a word, this review is supposed to be useful for the researchers who want to understand the research state of heat transfer of nanofluids.

Overview on the Preparation and Heat Transfer Enhancement of Nanofluids

Due to the great advantages of high thermal conductivity and strong heat exchange capacity, nanofluids have attracted great intrest in many heat exchange fields, such as thermal power plant, solar energy, automobile cooling, nuclear power facilities and so on. In this paper, it reviews the research progress of nanofluids including preparation process, suspension stability, thermal conductivity, viscosity,and gives emphasis to analyse the influence factor of nanofluid convective heat transfer.

The surfactants effect on the heat transfer enhancement and stability of nanofluid at constant wall temperature

Surfactants role in the enhancement of the heat transfer and stability of alumina oxide – distilled water nanofluid was introduced in this research, where there are limited studies that conjugate between the stability improvement and its effect on the heat transfer coefficients. Four weight concentrations for the experiment were used (0.1, 0.3, 0.6, and 0.9%) with 20 nm particle size under a constant wall temperature. The selection of appropriate surfactants weight was tested too by implementing three weight concentrations (0.5, 1, 1.5, and 2 %) related to each nanofluid concentration via measuring their effect on the zeta potential value. The heat transfer augmentation was tested through a double horizontal pipe under a constant wall temperature at entrance region with Reynolds number range (4000–11800). The results manifested the use of nanofluid worked on enhancement the heat transfer performance better than water, and the stable nanofluid elucidated better results.

A review on the thermal performance of nanofluid inside circular tube with twisted tape inserts

Working fluid with higher thermal conductivity and tube with better fluid mixing are two crucial elements for heat transfer enhancement in heat exchanger system. Hence, several methods and techniques have been explored to improve heat transfer efficiency, including dispersing nanoparticles into conventional heat transfer fluid and inserting instruments inside the tube of the heat exchanger. Studies have shown that nanofluid can improve heat transfer efficiency of the system due to its higher thermal conductivity and drastic Brownian motion of nanoparticles while inserts within tube can improve heat transfer efficiency by increasing axial velocity of working fluid for better fluid mixing. This article summarized 109 of journals from recent research on heat transfer enhancement of nanofluid flowing inside the tube with inserts as well as discussing the significant parameters that affected the system’s efficiency such as nanoparticles’ volume fraction, Reynolds number and types and configurations of inserts. Ultimately, analysis will be carried out to determine the most suitable modification of twisted tape inserts with the most optimum value of nanoparticle volume fraction for turbulence flow regime. Finally, some problems that need to be solved for future research such as agglomeration and pressure drop are discussed.

Experimental study of Zn-water nanofluid heat transfer enhancement through an oval twin impingement jet

An oval cross-sectional-area twin jet were studies experimentally studied under constant heat flux conditions to clarify the effect of both Zn-water nanofluid along with such oval twin jet on the thermal characteristic and provide the lack data in such field. The validation was conducted with comparable study and it showed acceptable deviation. The emerged results referred to that the Nusselt number is remarkably increase as the nanoparticle concentration, Reynold number and the distance between nozzles increase. The higher enhancement was found to be 2.1% at high Reynold number value (Re=1000), S/D=5 and nanoparticle concentration ϕ=0.5.

Dynamic stability, sedimentation, and time-dependent heat transfer characteristics of TiO2 and CNT nanofluids

Nowadays, the stability and heat transfer properties of nanofluids have been extensively studied. However, for the practical application, the dynamic stability, sedimentation, and fouling characteristics are also important issues. Whether nanofluids can maintain stable heat transfer characteristics during intermittent operation in the system is also a worthwhile issue. In this paper, the dynamic stability, sedimentation, and fouling characteristics as well as the time-dependent heat transfer characteristics of TiO2 and CNT nanofluids are investigated sequentially. The results show that compared with static condition, the dispersion stability of nanofluids is much better, and the sedimentation and fouling on solid surface are much less in dynamic condition. For the nanofluids in this paper, the sedimentation and fouling on solid surface are loose and can easily washed out after slight flushing. Rough surfaces are easier to adsorb the nanoparticles sedimentation and form fouling, but it can be greatly removed using ultrasonication. Long-term shutdown reduces the convective heat transfer enhancement of nanofluids, but it can be well restored after the action of ultrasonication.

Natural convection heat transfer enhancement of different nanofluids by adding dimple fins on a vertical channel wall

Abstract In this numerical study, natural flow and heat transfer of nanofluids with Al2O3, TiO2, Cu and CNT nanoparticles in a vertical channel with dimpled fins at Rayleigh number (Ra) of Ra = 3.25 × 107 to Ra = 1 × 108 are investigated by using the finite volume method. The obtained results revealed that, using CNT in volume fractions of 2% and 4% leads to significant heat transfer and at φ = 6%, using TiO2 nanoparticles has a great effect on Nu number enhancement. Also, using solid nanoparticles in base fluid causes more uniform heat transfer distribution, especially in areas close to heated surface and by adding more volume fraction in base fluid, temperature level reduces. In general, according to temperature contours, reduction of wall temperature depends on the increase of Ra and volume fraction and the type of solid nanoparticles.

Application of neural network on heat transfer enhancement of magnetohydrodynamic nanofluid

AbstractThe applications of neural networks (NNs) on engineering problems have been increased for obtaining high precision results. In this study, a new type of NN known as the group method of data handling (GMDH) is applied to obtain a formulation of a heat transfer rate. The numerical method of control volume‐based finite element method (CVFEM) is applied as a robust and reliable numerical approach for simulation of magnetohydrodynamic (MHD) flow of a nanofluid inside an inclined enclosure with a sinusoidal wall. A water‐based nanofluid with Cu nanoparticles is used as main fluid in our model. Maxwell–Garnetts (MG) and Brinkman models are applied to calculate effective thermal conductivity and viscosity of nanofluid, respectively. This study tries to find that GMDH‐type NN is a reliable technique for calculation of MHD nanofluid convective based on specified variables. Our findings clearly demonstrate that GMDH‐type NN is more reliable than the CVFEM approach and this technique could efficiently identify the patterns in data and precisely estimate a performance. Comprehensive parametric studies are done to disclose the impact of significant factors such as electromagnetic force, buoyancy, nanoparticle volume fraction, and direction of enclosure on heat transfer rates. According to obtained results, heat transfer rate rises with the growth of buoyancy effects, the concentration of nanoparticles, and slope of domain while it reduces when Hartmann number is increased.

Effect of Various Evaluation Criteria on Heat Transfer Enhancement of Nanofluids: A Case Study of Water-Based Cu2O Nanofluids

The numerical study investigates the effect of various comparison criteria on the forced convective heat transfer of water-based cuprous oxide nanofluids in a horizontal mini tube under uniform heat flux conditions. The forced convective flow regime was validated, and it was ensured that the free convection effects were not present. The temperature-dependent thermophysical properties were considered for the numerical simulation. The volume concentrations of the nanofluids were kept below 2% (i.e., 0.6%, 1.3% and 1.9%) as higher concentrations lead to agglomeration and sedimentation of nanoparticles. The various comparison criteria employed for the assessment of heat transfer enhancement were equal pumping power, equal velocity, equal mass flow rate and equal Reynolds number criterion. The enhancements in heat transfer coefficient (at ϕv = 1.9% and base fluid Re = 1380) were 7.7%, 4.9%, 3.6% and 3.3% when assessed on the basis of equal Reynolds number, equal velocity, equal mass flow rate and equal pumping power, respectively. It was found that the enhanced heat transfer of the nanofluids should preferably be examined on the basis of equal pumping power criterion instead of above-mentioned other three criteria. The discussion on the invalidity of three evaluation criteria based on Reynolds number, velocity and mass flow rate has also been made.

Experimental investigation on heat transfer characteristics of various nanofluids in an indoor electric heater

Heat transfer characteristics of an electric heater were experimentally investigated by using various fluids in this paper, including Cu-EGW (a mixture of ethylene glycol and DI-water), Al2O3-EGW, Fe3O4-EGW nanofluids. A 4:6 mixture of ethylene glycol and deionized water was used as the base liquid. All these nanofluids were prepared by ultrasonic treatment, and nanoparticle mass concentration of samples varies from 0.5% to 2%. In addition, natural convective heat transfer of Fe3O4-EGW nanofluid in an electric heater was carried out by considering an effect of different magnetic fields. The results indicated that heat transfer performance of Cu-EGW nanofluid was significantly higher than the Al2O3-EGW and Fe3O4-EGW nanofluids, and the heating efficiency of the Cu-EGW nanofluid increased with the mass concentration of Cu particles. Compared with that of the base fluid, equilibrium temperature values of electric heaters filled with 2.0% Cu-EGW, 1.0% Al2O3-EGW and 1.0% Fe3O4-EGW nanofluids increase by 13.18%, 3.77% and 4.52%, respectively. It was also found that the magnetic field had a positive effect on the heat transfer enhancement of the Fe3O4-EGW nanofluid. In addition, for the 0.5% Fe3O4 nanofluid under a magnetic intensity of 100 mT, the equilibrium temperature on the middle fin increases by 14.68%.