Effect Of Nanofluid Concentration Research Articles

Improving sensible heat storage in a vertical annular pipe subject to variable inlet boundary condition using TiO2/water nanofluid: Numerical study

A computational fluid dynamics (CFD) analysis is conducted to investigate the thermal performance of unsteady free convection of TiO2/water nanofluids. The study process within a coaxial heat exchanger system. The model is based on the mixture Buongiorno approach. Due to the axisymmetric conditions, the study is carried out in two dimensions, and the conservation equations are reformulated in dimensionless form. The obtained PDE system is Discretized using the finite element method. The TiO2 concentration heterogeneity, resulting from thermophoresis and Brownian motion is considered. The presentation of the results encompassed isotherms, nanoparticle volume fraction distributions, and streamlines. The validation of the model shows a good agreement with the experimental results. The impact of the mass fraction’s nanoparticles ( 0.01 ≤ ϕ ≤ 0.04 ) and the Rayleigh number ( 10 3 ≤ Ra ≤ 10 8 ) on the heat transfer performance are analyzed. The parametric study shows that an increase in the Rayleigh number has no effect on heat transfer enhancement. Unlike for Ra = 10 6 where an increase in Nusselt number is observed. It was found also that the effect of nanofluid concentration on the Nusselt number was more noticeable in high Rayleigh cases due to the convection-driven heat transfer.

Experimental Study on the Effect of TiO2–Water Nanofluid on Heat Transfer and Pressure Drop in Heat Exchanger with Varying Helical Coil Diameter

The growing demand for efficient heat exchangers has promoted extensive research in exploring advanced heat transfer fluids and novel geometries. This paper investigates the heat transfer and pressure drop characteristics in helical coil heat exchanger employing water-based TiO2 as nanofluid. The utilization of nanofluids offers promising enhancements in thermal conductivity and convective heat transfer in heat exchanger applications. The effect of nanofluid concentration and flow rate on heat transfer and pressure drop with varying helical coil diameter performance is investigated. Experimental tests were conducted using a heat exchanger with different helical coil pipe diameters of 9.53mm, 12.7mm and 15.88mm with constant pitch of 30mm and varying concentrations of TiO2 nanoparticles in water (ranging from 0.1% to 0.5% by volume). The heat transfer coefficient and pressure drop were measured at different operating conditions. The results shows that the addition of TiO2 nanoparticles to water significantly enhanced the heat transfer performance in the helical coil heat exchanger. There is an enhancement in heat transfer coefficient with increasing nanofluid concentration and with increase in pipe diameter. The maximum enhancement in heat transfer coefficient is observed at nanofluid concentration of 0.5% and for pipe diameter of 15.88 mm. However, there is increase in pressure drop with increase in nanofluid concentration and with decreasing pipe diameter. The pressure drop found to be higher for nanofluids compared to pure water. The maximum pressure drop is observed at a concentration of 0.5% and for pipe diameter 9.53mm. In conclusion, the use of a water-based TiO2 nanofluid in a helical coil heat exchanger offers improved heat transfer performance compared to pure water. However, the pressure drop also increases with nanofluid concentration and decreasing pipe diameter. Therefore, a trade-off between heat transfer enhancement and pressure drop should be considered in the design and operation of such heat exchangers.

Effect of SiO2 nanofluid with different concentrations on the wettability of coal

Water-based SiO2 nanofluid, a wetting agent, has been proved to be feasible in improving the control effect of coal seam water injection against coal and gas outburst. However, the effect of nanofluid concentration on the control effect is not clear. Therefore, it is necessary to investigate the wettability-enhancing effect of nanofluid with different concentrations. In this paper, firstly, the effect of SiO2 nanofluid with different concentrations on water adsorption capacity of coal was obtained. Then, the wettability-enhancing effect of SiO2 nanofluid with different concentrations was investigated by contact angle tests. Finally, the effect of nanofluid concentration on the wettability enhancement of coal was revealed. The results showed that increasing the nanofluid concentration can enhance the water adsorption capacity and wettability of coal. In addition, the wettability-enhancing effect of nanofluid gradually got worse with time, while the stability of wettability-enhancing effect gradually got better. Furthermore, the 0.5 wt% nanofluid had the best sustainability and stability of the wettability-enhancing effect, while 1.0 wt% had the worst sustainability and stability. The research achievements could provide important basis for the selection of nanofluid concentrations in coal seam water injection.

Numerical simulation and multi-objective optimization of heat transfer of Al2O3/water nanofluid in rectangular ducts

Laminar flow of Al2O3/water nanofluids in rectangular ducts with different aspect ratios (AR) were simulated numerically. Both heat transfer coefficient and pressure drop of nanofluids are higher than the base fluid and increase with nanofluid concentration in ducts of all aspect ratios. For a duct with AR = 2, the heat transfer coefficient of nanofluids with a concentration of 5% vol. is on average 22% higher than the base fluid. Its pressure drop is about 2.5 times of the base fluids. The effect of nanofluid concentration on the heat transfer coefficient is more significant in ducts with a lower aspect ratio. The heat transfer coefficient of a 5% vol. nanofluid in a duct with AR = 1 is about 24% larger than the base fluid; this value is about 18% for a duct with AR = 6. The effect of nanofluid concentration on the pressure drop of all ducts is identical. The results of the numerical simulation were used for training a multi-Layer perceptron artificial neural network (MLP-ANN) model. The ANN model predicts the pressure drop and heat transfer coefficient of nanofluids in rectangular ducts very accurately. The maximum differences between the values of heat transfer coefficient predicted by the ANN and those obtained from the numerical simulation is about 0.11%, and that of the pressure drop is about 0.65%. Multi-objective NSGA-II optimization algorithm was applied to optimize the nanofluid flow in rectangular ducts. In optimization, the goal was to maximize the heat transfer coefficient and minimize the pressure drop. The values of objective functions were evaluated by the resulting ANN model. Optimization for ducts with each aspect ratio was performed. Optimization was also done for all channels. Pareto fronts were obtained from optimization. The best solution for each optimization is determined by two decision-making methods. For the overall optimal solution, nanofluid concentration, Reynolds number, and the duct aspect ratio are 2.28% vol., 400, and 6, respectively which are the same as the optimal solution of the duct with an aspect ratio of six.

Experimental Study on Supercooling Phenomenon and Supercooling Degree of Nanofluids

In recent years, nanofluid has gradually entered people's field of vision due to its unique cold storage performance. Hybrid nanofluid has a more prominent effect. In order to reduce the supercooling degree of the nanofluid and obtain a practical and effective method to reduce the supercooling degree, the nano-particle graphene oxide and Al2O3 are added into deionized water ultrasonically to configure the nanofluid, and then the temperature is cooled. The effect of nanofluid concentration and different initial fluid temperature on the nanofluid subcooling degree is obtained when the ultrasonic time is 120min; when the nanofluid concentration is 0.15%wt, the nanofluid subcooling degree is the lowest, and the nanofluid is supercooled at this time The temperature is 2.8°C, which is the optimal condition for undercooling research.

Statistical modelling for the Ultrasonic photodegradation of Rhodamine B dye using aqueous based Bi-metal doped TiO2 supported montmorillonite hybrid nanofluid via RSM

In this study, a novel aqueous based 10% w/w copper (Cu)-nickel (Ni) doped titania (TiO2) supported montmorillonite – k 10(MMT- k 10) clay based hybrid nanofluid at various mixing ratios (Cu: Ni) of 100:0, 75:25, 50:50, 25:75, and 0:100 are prepared using hydrothermal process. The photocatalyst activity has been analysed by degrading the Rhodamine B in a photoreactor under a visible-light source. The Diffuse reflectance spectrum results showed a maximum of 19% reduction in the TiO2 band gap energy by the addition of the metals in the ratio of 75:25. Furthermore, the clay addition improved the adsorption surface area and porosity of the photocatalyst. The effect of nanofluid concentration (1 to 2 vol%), ultrasonication time (before photocatalysis – 15 to 30 min), reaction time (20 to 50 min) and the distance between reactant and the lamp (4 to 10 cm), on the photocatalytic degradation of dye solution are analysed using response surface methodology (RSM). The fine-tuning of the input parameters shows 97% photocatalytic degradation of the effluent within 60 min of reaction time. Simultaneously, Analysis of variance (ANOVA) study has been performed to understand the significant effect of the input parameters on the variation of response variable. Based on the results, a new quadratic correlation and a possible photocatalytic degradation mechanism are proposed.

Mixed convection heat transfer of AL2O3 nanofluid in a horizontal channel subjected with two heat sources

Mixed convection flow is investigated numerically for nanofluid flow and heat transfer in a horizontal channel considering two localized heat sources compared with pure fluid. The channel’s walls are insulated and the heat sources are at the center of the channel. Al2O3 nanoparticles are employed to modify the thermal conductivity of the base fluid. The effect of different parameters including Richardson number, Reynolds number, thermal conductivity, sources separation distance and the length-to-height ratio of heat sources is investigated. The results indicate that by enhancing the Richardson number from 1 to 10, the heat transfer from the source surfaces slightly increases; however, no significant effect is observed on thermal behavior. Increasing Reynolds number modifies heat transfer from sources and has a large effect on the streamlines and isotherms. In Richardson number of 5, for Reynolds number of 5, 50, 100, 150, the Nusselt number is 1.01, 4.50, 14.11 and 22.13, respectively. Furthermore, for a higher sources thermal conductivity, heat transfer increases due to the lower thermal resistance. The increase in average Nusselt number with changing the dimensionless thermal conductivity in the range of $$1 \le \bar{k} \le 100$$ is 314%. By examining the length-to-height ratio of heat sources, the results show that heat transfer decreases initially and then increases for higher values of length-to-height ratios. Furthermore, the heat sources separation distance shows a pronounce influence on heat transfer and thermal distribution. Besides, the results show that the effect of nanofluid concentration on average Nusselt number is more significant at low Reynolds number. The increase of average Nusselt number for Reynolds numbers of 5, 80 and 150 is 25%, 15% and 6.5%, respectively.

Natural Convection Heat Transfer in a Shell and Helical Coil Heat Exchanger Using non-Newtonian Nanofluids

AbstractNanofluids have gained much attention due to excellent thermal properties. In this study, natural convection heat transfer behavior of three different types of non-Newtonian nanofluids in a shell and helical coil heat exchanger has been investigated experimentally under unsteady state conditions. Nanofluids were prepared by dispersion of Al2O3, Fe2O3 and CuO nanoparticles in an aqueous solution of carboxymethyl cellulose (CMC) (base fluid). Nanofluids of different concentrations (0.2, 0.4, 0.6, 0.8 and 1.0 wt%) were prepared by dispersing Al2O3, Fe2O3 and CuO nanoparticles in base fluid using probe sonication process. In the present study, the effect of shell-side nanofluid concentration, tube-side fluid (heating medium) temperature and flow rate parameters on heat transfer has been investigated.Results indicated that the addition of nanofluid has intensified heat transfer as indicated by the higher temperature of nanofluid when compared to base fluid. Out of the three materials used in the study, CuO nanofluid attained the highest temperature because of its higher thermal conductivity. Heat transfer rate decreased with time continuously for all the experimental conditions. Enhancement in heat transfer initially was higher compared to later times. At longer time the enhancement is less due to the lower buoyancy forces prevailing due to lower driving force. A maximum enhancement in heat transfer rate of 29.5 % has been obtained initially. The effect of nanofluid concentration on heat transfer rate with time exhibited different behavior compared to the effect of inlet temperature and flow rate.

Numerical Simulation of Flow and Heat Transfer Characteristics of CuO-Water Nanofluids in a Flat Tube

In this paper, water and CuO-water nanofluids are selected as working fluids. The characteristics of fluid flow and heat transfer in a heat transfer tube are analyzed by means of numerical simulation. The effect of nanofluid concentration on the flow and heat transfer characteristics of the flat tube under the condition with a Reynolds number of 6000~10000 is analyzed and compared with that of the circular tube. The results show that the addition of nanoparticles in the nanofluid has little effect on the velocity and temperature distribution in the flow channel. With the increase of nanofluid concentration, the heat transfer coefficient and flow resistance of the fluid increased. And the comprehensive evaluation factor was 2.51~3.29, which had the effect of enhancing heat exchange. There is a similar trend in the same concentration with different Reynolds numbers. Compared with the circular tube, the nanofluid has a better ability to enhance heat transfer when it flows in the flat tube. Under conditions with the same fluid concentration, the effect of the application of the nanofluids on the flat tube is better.

STUDY ON EFFECT OF NANOFLUIDSON HEAT TRANSFER CHARACTERSTIC OF HEAT PIPE

With the increase in requirement of advanced technical equipmentnn , of which there basic initial workn is carried out on the applications,n which used heat pipes for heat transfer. Heat pipes are one specific type of heat exchangers, having very wide application in electronics and other fields, because of its compactess,n high efficiency, less number of components and no need for external circulation of working fluid. This heat pipes previously carryingnn conventionalnn fluid as working medium inside them. But in recent yearsn nanofluidsnn in heat pipesn have attracted a notable attention due to its superior heat transfer properties. .nn Addition of nano size solid particles having high thermal conductivity to the working fluid of low conductivity, will enhance the overall heat transfer coefficient of the system and in turn the efficiency.n The effect of filling ratio, volume fraction of nano particles on thermal performance in various kind of heat pipes with different base fluids under various operating conditions has been discussed . This paper discusses relativity of total heat resistance between the heat pipe with nano fluid and with existing fluids. Also the basic work of heat pipe nanofluid and the effect of nanofluid concentration on heat pipe are discussed. The studied results have shown a remarkable influence on decrease in thermal resistance of the heat pipe wall.nn

Two-phase mixture model for nanofluid turbulent flow and heat transfer: Effect of heterogeneous distribution of nanoparticles

In this work, a two-phase mixture model for evaluation of flow and heat transfer performance of SiO2/water nanofluids under turbulent flow was proposed by considering the heterogeneity of concentration due to crossed effect and the influences of shear rate, viscosity gradient, thermophoresis and Brownian motion on the diffusion of the nanoparticles. The effects of Peclet number, Reynolds number, nanoparticle size and nanofluid mean concentration on the distribution of nanoparticles have been evaluated. The values of thermal conductivity and viscosity as the main thermophysical properties of nanofluids changed across different layers of the liquid due to the heterogeneous distribution of concentration. It was observed that an increase in the Peclet number caused heterogeneity in the distribution of the properties. The achieved nanoparticle distribution has been implemented for analysis of nanofluid using two-phase mixture model. It was found that the effect of nanofluid concentration on the Nusselt number was more noticeable in lower Reynolds numbers due to the insignificant effect of flow momentum on heat transfer. The maximum of 43.9% enhancement in convection heat transfer was achieved by dispersion of 4% SiO2 nanoparticles inside DI-water at Re=25,000.

Exergy analysis of a shell-and-tube heat exchanger using graphene oxide nanofluids

Nanofluids are the new-generation heat transfer fluids largely used in heat exchangers for thermal energy transport applications. In this paper, graphene oxide was prepared in-house and used for nanofluid development and characterization. The graphene oxide was prepared by oxidizing purified natural flake graphite via the modified Hummers method. The morphology and structure of fabricated graphene oxide were characterized using X-ray diffraction analysis (XRD) and a scanning electron microscope (SEM). The graphene oxide nanofluids were prepared at 0.01 and 0.1wt.% concentrations. The particle size and zeta potential of nanofluids were measured using the dynamic light scattering (DLS) technique. The rheological behaviors of nanofluids were investigated at 25 and 40°C at different shear rates (10–1001/s). Thermal conductivity of nanofluids was measured using the transient hot wire method at 25 and 40°C. Exergy analysis showed that increasing the graphene oxide concentration from 0.01wt.% to 0.1wt.% resulted in 8.7% and 18.9% thermal conductivity enhancement at 25 and 40°C, respectively. Furthermore, the thermal performance of graphene oxide nanoparticles in a shell-and-tube heat exchanger was studied experimentally. The effect of nanofluid concentration, flow rates, temperature inlet and flow regime on the system’s exergy loss was studied experimentally. The results showed that using graphene oxide nanofluids as the hot fluid resulted in less exergy loss in the shell-and-tube heat exchanger under both laminar and turbulent conditions. Comparing the exergy loss of graphene oxide nanofluids to distilled (DI) water showed that DI water caused 22% and 109% higher exergy loss than in laminar conditions.

Effect of nanofluid concentration on two-phase thermosyphon heat exchanger performance

Abstract An approach - relaying on application of nanofluid as a working fluid, to improve performance of the two-phase thermosyphon heat exchanger (TPTHEx) has been proposed. The prototype heat exchanger consists of two horizontal cylindrical vessels connected by two risers and a downcomer. Tube bundles placed in the lower and upper cylinders work as an evaporator and a condenser, respectively. Distilled water and nanofluid water-Al2O3 solution were used as working fluids. Nanoparticles were tested at the concentration of 0.01% and 0.1% by weight. A modified Peclet equation and Wilson method were used to estimate the overall heat transfer coefficient of the tested TPTHEx. The obtained results indicate better performance of the TPTHEx with nanofluids as working fluid compared to distilled water, independent of nanoparticle concentration tested. However, increase in nanoparticle concentration results in overall heat transfer coefficient decrease of the TPTHEx examined. It has been observed that, independent of nanoparticle concentration tested, decrease in operating pressure results in evaporation heat transfer coefficient increase.

Effect of nanofluid concentration and composition on laminar jet impinged cooling of heated steel plate

In this paper, an experimental investigation of heated steel surface cooled by laminar nanofluid jets and its comparison with water jets are presented. The effects of concentration and jet velocity of TiO2 based nanofluid on cooling rate are evaluated experimentally. Further, the cooling rates of TiO2, Al2O3, and SiO2 nanofluids with same concentration and velocity are compared. The total heat flux is deduced from the experimentally obtained cooling curves by using a one-dimensional finite volume method based transient inverse heat transfer model. It is found that heat transfer is enhanced using nanofluid jets when compared to water. Increase in concentration of TiO2 nanoparticle in nanofluid leads to an increase in CHF. Further, it is also observed that the shift from film boiling to transition boiling is faster for nanofluid jet cooled surface.

The Effect of Nanofluid Concentration on the Cooling System of Vehicles Radiator

Experimental investigation on forced convection heat transfer is applied to vehicles’ radiator filled with AL2O3 water nanofluid with different concentrations: 0.1%, 0.5%, 1%, 1.5%, and 2% by volume. The experiments are done for three cases, each case corresponds to different heat load, coolant flow rate, and air flow rate to simulate the vehicle engine cooling system at various loads relevant to the cooling system of Toyota Yaris 2007. The coolant and air heat transfer coefficients, Nusselt numbers, heat rate lost by the coolant and absorbed by the air, heat exchanger effectiveness, overall heat transfer coefficients, Reynolds number, and the pumping power are calculated. Log mean temperature difference (LMTD) and effectiveness-number of transfer units ( ε-NTU) are used to determine the outside air heat transfer coefficient. Results show gradual enhancement in the heat transfer with concentrations 0.1%, 0.5%, and 1% by volume (optimum at 1%); however deterioration occurs at concentrations 1.5% and 2%.

Effect of nanofluid concentration on the performance of circular heat pipe

The goal of this paper is to experimentally study the behavior of nanofluid to improve the performance of a circular heat pipe. Pure water and Al 2O 3-water based nanofluid are used as working fluids. An experimental setup is designed and constructed to study the heat pipe performance under different operating conditions. The effect of filling ratio, volume fraction of nano-particles in the base fluid, and heat input rate on the thermal resistance is investigated. Total thermal resistance of the heat pipe for pure water and Al 2O 3-water based nanofluid is also predicted. An experimental correlation is obtained to predict the influence of Prandtl number and dimensionless heat transfer rate, K q on thermal resistance. Thermal resistance decreases with increasing Al 2O 3-water based nanofluid compared to that of pure water. The experimental data is compared to the available data from previous work. The agreement is found to be fairly good.