Different Concentrations Of Nanofluids Research Articles

Stability Evaluation of Nanofluids Suitable for Enhanced Oil Recovery

The evaluation of metal oxides nanoparticles stability in the base fluids has become a major aspect in enhanced oil recovery process in recent years. Physical and chemical properties of ZnO nanofluids have caught attention of many researchers because they are easily dispersed in the base fluids, better convective coefficient of heat transfer, and wider bandgap which make them remarkable nanofluids candidate compared to other metal oxides. In this study, the stability of nanofluid of zinc oxide nanoparticles was evaluated using different stability tests and analysis. However, ZnO nanoparticles were synthesized using sol-gel method and nanofluids of different concentrations were prepared. The prepared nanoparticles were characterized using various characterization techniques such as XRD, FTIR, TEM, and Zeta sizer. The stability of prepared nanofluids was investigated using sedimentation test, UV-vis spectrophotometer, and zeta analyzer. Based on physical investigation and UV-vis spectra observations, ZnO nanoparticles in base fluids have shown a good colloidal stability in addition to their high zeta potential values of-43.7 (mV) after seven days which makes it a successful potential candidate for enhanced oil recovery applications.

Experimental study and ANFIS modelling of the thermophysical properties and efficacy of GNP-Al2O3 hybrid nanofluids of different concentrations and temperatures

This study delves into an extensive investigation of the thermophysical properties and heat transfer efficacy of a hybrid nanofluid incorporating graphene nanoplatelets and γ-Al2O3 nanoparticles dispersed in deionised water. The nanofluids were characterised for their viscosity (µ), thermal conductivity (λ), and electrical conductivity (σ) over a 15–40 °C temperature range for varying nanoparticle loading (0.1–0.4 vol%). The experimental results revealed notable enhancements in µ, λ, and σ with increasing nanoparticle concentration, while µ decreased at elevated temperatures as λ and σ increased. At the highest concentration (0.4 vol%), µ increased by 21.74%, while λ and σ exhibited peak enhancements of 17.82% and 393.36% at 40 °C. An Adaptive Neuro-fuzzy Inference System (ANFIS) model was devised to enhance predictive precision by meticulously optimising the number of membership functions (MFs) and input MF type. The ANFIS architecture that exhibited the most remarkable agreement with the experimental data for µ, λ, and σ was found to utilise the Product of Sigmas, Difference of Sigmas, and Generalized Bell MFs, respectively, with corresponding input MF numbers being 2–3, 3–2, and 3–2. The optimal ANFIS model for µ, λ, and σ exhibits a higher prediction accuracy with an R2 value of 0.99965, 0.99424 and 0.99995, respectively. The Figure of Merit analysis using Mouromtseff Number identified an optimal nanoparticle concentration range of 0.1–0.2 vol% for enhanced heat transfer performance with a reasonable µ increase. This range guides practitioners in utilising hybrid nanofluids effectively while managing potential drawbacks.

Doped CeO2/water nanofluids analyzed the performance of thermal conductivity and heat transfer: An experimental and theoretical investigations

A combined experimental and theoretical study on thermal conductivity, heat transfer specific heat, and electronic properties has been done for doped CeO2/water nanofluid. First, the sol-gel method was implemented for the synthesis of doped CeO2 nanoparticles and then a mixture of nanoparticles with different concentrations of nanofluid. X-ray diffraction and SEM analysis confirm the structural phase purity and homogeneous mixing of nanofluids. Experimental thermal conductivity and specific heat of pure and 4f-doped CeO2 were estimated and found very close to our theoretical calculations. Experimental investigations have been carried out for the measurement of heat transfer using pure and doped CeO2/water nanofluid as the coolant. The experiments were aimed at determining the heat transfer and other thermal properties with different concentrations and with various fluid with Reynolds number 2500 and 3500. The heat transfer coefficient of nanofluids increases not only with an increase in the volume flow rate of the hot water but also increases with increase in the atomic number of dopant elements in CeO2. Electronic states show variation in band gap with doping which may also play an important role in the improvement of solar collectors. It is clear from experimental and theoretical findings that the thermal and electronic properties depend on number of valance electrons. Hence doping of 4f-element in CeO2 plays a vital role to increase the thermal conductivity and tuning of electronic properties leads to many applications in thermal sensors and solar cell-based industries.

Ac-Susceptibility Studies of the Energy Barrier to Magnetization Reversal in Frozen Magnetic Nanofluids of Different Concentrations

We used ac-susceptibility to measure the blocking temperature, TB, and energy barrier to the magnetization reversal, EB, of nanomagnetic fluids of different concentrations, c. We collected data on five samples synthesized by dispersing Fe3O4 nanoparticles of average diameter ⟨D⟩ = 8 nm in different volumes of carrier fluid (hexane). We found that TB increases with the increase in c, a behavior predicted by the Dormann–Bessais–Fiorani (DBF) theory. In addition, our observed TB vs. c dependence is excellently described by a power law TB = A∙cγ, with A = 64 K and γ = 0.056. Our data also show that a Néel–Brown activation law τT=τ0exp⁡EBkBT describes the superspin dynamics in the most diluted sample, whereas an additional energy barrier term, Ead, is needed at higher concentrations, according to the DBF model: τT=τrexp⁡EB+EadkBT. We found EB/kB = 366 K and additional energy barriers Ead/kB that increase linearly with the common logarithm of the volume concentration, from 138 K at c = 8.3 × 10−4% to 745 K at c = 4 × 10−2%. These results add to our understanding of the contributions by different factors to the superspin dynamics. In addition, the quantitative relations that we established between the TB, Ead, and c support the current efforts towards the rational design of functional nanomaterials.

Investigation of the effect of Fe3O4/SiO2 nanofluid on asphaltene adsorption and wettability alteration in hydrocarbon reservoirs: Optimization of nanocomposite composition and nanofluid concentration

One of the most efficient ways to extract hydrocarbons is to use nanoparticles for wettability alteration, to address dwindling reservoirs and growing energy demand. Another crucial factor is inhibiting asphaltene precipitation, which can cause damage to production components and alter the rock's wettability and permeability. This study investigates the impact of synthesized Fe3O4, SiO2, and Fe3O4/SiO2 nanomaterials on wettability alteration and asphaltene removal in an oil/water system at two temperatures (25 °C and 80 °C). The nanocomposites with various ratios were manufactured with the aid of the sol-gel method and characterized using FTIR, XRD, and dynamic light scattering analysis. The stability of different concentrations of nanofluids was assessed via sedimentation tests and zeta potential measurements. According to the results, there was a reduction in both surface energy and oil area fraction from 89.46 to 8.13 mN/m and from about 1–0.075, respectively. Maximum wettability alteration (from 155° to 32°) was achieved at the optimum condition (0.075 wt% of C1000 at 80 °C). The C1000 nanocomposite played a significant role as an inhibitor in shifting the onset point to higher concentrations of n-heptane compared to Fe3O4 and SiO2 nanoparticles. Furthermore, nanomaterials have a better association with the Langmuir model, and the asphaltene particles are adsorbed homogeneously and in the form of one layer of adsorbents. The results of this study can assist the petroleum sector in better controlling asphaltene precipitation and enhancing oil recovery by C1000 nanoparticles, leading to a higher recovery rate and a more cost-effective production approach.

Study on Heat Transfer Characteristics of Graphene Nanofluids in Mini-Channels of Thermal Integrated Building.

Two kinds of rectangular mini-channels of different sizes were designed and fabricated for testing the convective heat transfer characteristics of graphene nanofluids. The experimental results show that the average wall temperature decreases with the increases in graphene concentration and Re number at the same heating power. Within the experimental Re number range, the average wall temperature of 0.03% graphene nanofluids in the same rectangular channel decreases by 16% compared with that of water. At the same heating power, the convective heat transfer coefficient increases with the increase in the Re number. The average heat transfer coefficient of water can be increased by 46.7% when the mass concentration of graphene nanofluids is 0.03% and the rib-to-rib ratio is 1:2. In order to better predict the convection heat transfer characteristics of graphene nanofluids in small rectangular channels of different sizes, the convection heat transfer equations applicable to graphene nanofluids of different concentrations in small rectangular channels with different channel rib ratios were fitted, based on factors such as flow Re number, graphene concentration, channel rib ratio, Pr number, and Pe number; the average relative error (MRE) was 8.2%. The mean relative error (MRE) was 8.2%. The equations can thus describe the heat transfer characteristics of graphene nanofluids in rectangular channels with different groove-to-rib ratios.

Numerical Study on the Heat Transfer Characteristics of Cu-Water and TiO2-Water Nanofluid in a Circular Horizontal Tube

A numerical simulation of convective heat transfer coefficient (hconv) was studied with Cu-Water and TiO2-Water nanofluids flowing through a circular tube subjected to uniform wall heat flux boundary conditions under laminar and turbulent regimes. Four different concentrations of nanofluids (ɸ = 0.5, 1, 1.5 and 2%) were used for the analysis and the Reynolds number (Re) was varied from laminar (500 to 2000) to turbulent flow regime (5000 to 20,000). The dependence of hconv on Re and ɸ was investigated using a single-phase Newtonian approach. In comparison to base fluid, average hconv enhancements of 10.4% and 7.3% were noted, respectively, for the maximum concentration (ɸ = 2%) and Re = 2000 for Cu-Water and TiO2—water nanofluids in the laminar regime. For the same ɸ under the turbulent regime (Re = 20,000), the enhancements were noted to be 14.6% and 13.2% for both the nanofluids, respectively. The random motion (Brownian motion) and heat diffusion (thermophoresis) by nanosized particles are the two major slip mechanisms that have more influence on the enhancement of hconv. In addition, the Nusselt number (Nu) of the present work was validated for water with the Shah and Dittus Boelter equation and found to have good agreement for both the regimes.

Interfacial tension reduction of hybrid crude-oil/mutual-solvent systems under the influence of water salinity, temperature and green SiO2/KCl/Xanthan nanocomposites

In order to maximize oil recovery, combined enhanced oil recovery (EOR) methods can be used, which benefit from several mechanisms simultaneously. The application of nanotechnology and mutual solvents were studied separately in recent years. Mutual solvents have the ability to dissolve in both aqueous and oil phases and can show similar performance to surfactants in the water–oil interface. In this study, the effect of ethanol and methyl ethyl ketone solvents with and without a new nanocomposite on the reduction of interfacial tension (IFT) as a mechanism of the main EOR has been examined. The addition of these solvents to nanofluids is a new strategy that enhances the reactions at the interface of the two phases and improves the performance of the IFT mechanism. Also, diluted formation water samples were used as the simplest and most accessible smart water and synergistic effects on the system were investigated. Mutual solvents were tested at 5, 10, and 15 % by volume with and without nanocomposite at 25, 50 and 75 °C. In this way, different parameters of salinity, temperature, different concentrations of solvents and nanocomposite on IFT reduction were investigated. According to the results, each of these processes separately has positive effects in reducing IFT. But the combination of smart water - mutual solvent - nanocomposite showed the best effect in reducing IFT. The addition of solvents to water and nanofluids has a good potential to reduce IFT in reservoirs with high temperature and high salinity conditions. The optimum concentration of nanocomposite in the presence and absence of solvent was 1000 ppm, which shows that the optimum concentration NCs for IFT reduction is not affected by the presence of the solvent. But adding solvent to different concentrations of nanofluid has positive effects in reducing IFT. In general, methyl ethyl ketone has a stronger effect on reducing IFT than ethanol. Finally, the minimum IFT was observed for a mixture of 1000 ppm nanocomposite and 15 % methyl ethyl ketone with 50 % formation water as the base fluid at the temperature of 75 °C.

Thermophysical properties and contact angle of ethylene glycol/2D graphitic carbon nitride nanofluids with different metal substrates for solar applications

In this work, two dimensional graphitic carbon nitride (2D g-C3N4) nanomaterials is prepared by the combustion approach. The synthesised material is analysed for its structural and morphological properties using X-ray diffractometer and Transmission electron microscopy instruments. Further, pure ethylene glycol (EG), 90:10%, 70:30%, and 50:50% combination of EG/Water are used as base fluid to prepare 0.01, 0.03 and 0.05 wt% concentrations of 2D g-C3N4 nanofluids. The main objectives of this study are to find thermal conductivity, viscosity and contact angle of 2D g-C3N4 based nanofluids. The thermal conductivity of nanofluids increases with the increase of wt.% of 2D g-C3N4 in EG/Water. The viscosity of nanofluids decreases with the increase of concentrations of 2D g-C3N4 in EG/Water. It is found that the 50:50% combination of EG/water with 0.05 wt% of 2D g-C3N4 nanofluids exhibit enhanced thermal conductivity and low viscosity than other combinations. Further, Different concentrations of nanofluids are dropped on copper, aluminium, mild steel and stainless steel substrates to study the static contact angle. Results reveal that aluminium substrate exhibit excellent wettability (θ = 7.7°) with the combination of 90:10% (EG/Water) with 0.05 wt% of 2D g-C3N4. This study can deliver the effective performance in solar collectors, solar steam generation, solar heating and cooling.

CFD analysis of a flat tube with semi‐circular fins using graphene nanofluid and to compare performance with square type of fins

AbstractCFD analysis on a flat tube with semi‐circular fins under laminar flow conditions was performed with graphene‐based nanofluids considering the nanofluids as incompressible. Different simulations were performed at four different concentrations of nanofluids (0.01%, 0.1%, 0.2%, and 0.4%) and at different volume flow rates (4, 6, 8, and 10 LPM) and at four different forced convective heat transfer coefficients at different wind velocities at 300 K (50, 100, 150, and 200 W/m2 K). It was observed that with an increase in the concentration of nanoparticles in nanofluids, the thermal conductivity of base fluid water was increased (at 353 K the nanofluid of 0.4% volume concentration, the thermal conductivity of nanofluid increased by 200% with respect to base fluid). Graphene‐based nanofluids have higher effectiveness than most nanofluids hence it is considered for the analysis, at 0.4% concentration of nanofluid the effectiveness observed was 36.84% at 4 LPM, and for water, the effectiveness was 28.22% under similar conditions. The effect of flow rate on temperature drop was significant. At 4 LPM and at 0.4% of nanofluid, an outlet coolant temperature of 333 K was observed whereas the water outlet temperature at 10 LPM is 346.13 K. The effect of forced convective air heat transfer coefficient was significantly high. At h = 50 W/m2 K the outlet temperature of 0.4% nanofluid at 4 LPM was 345.25 K and at h = 200 W/m2 K, the outlet coolant temperature was 333.47 K. A single tube of the radiator was considered for the analysis whereas the original radiator consists of 50 tubes due to problems of Ansys in meshing.

Experimental Core Flooding Investigation of New ZnO-γAl2O3 Nanocomposites for Enhanced Oil Recovery in Carbonate Reservoirs.

Generally, crude oil production in mature oil reservoirs is difficult. In this regard, some nanoparticles have been used to upgrade injected water into oil reservoirs. These nanoparticles can be used in a variety of injectable waters, including smart water (SMW) with special salinity. This study aims to evaluate the performance of the injection of SMW with ZnO-γAl2O3 nanoparticles in enhanced oil recovery (EOR). The performance of SMW with ZnO-γAl2O3 nanoparticles in regard to contact angle (CA), interfacial tension (IFT) reduction, and oil production with core flooding tests was investigated. The newly prepared ZnO-γAl2O3 structure was characterized by energy dispersive X-ray (EDX), Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) analyses in this research. The effects of different concentrations of nanofluids on zeta potential (ZP) and conductivity were investigated. The ZP test confirmed the results of the stability tests of the developed nanofluids in water-based solutions. After the introduction of ZnO-γAl2O3 nanoparticles into the formation of brine and SMW solutions, oil-water (O/W) IFT was reduced. Based on the results, the IFT decreased more when nanoparticles and ions were present in the system. The results of the present study showed that at the concentration of SW+300 ppm ZnO-γAl2O3, the IFT value reached 11 mN/m from 27.24 mN/m. The results of the CA tests showed that improving the capabilities of salt water in the presence of nanoparticles has resulted in a very effective reduction. Also, in this regard, very hydrophilic wettability was achieved using SMW with stable nanoparticles. Moreover, the results of the present study showed that at the concentration of SMW+300 ppm ZnO-γAl2O3 nanoparticles, the CA value reached 31 from 161°. In the end, the solution of SW+300 ppm ZnO-γAl2O3 improved the OR by 15 and 24%. This research indicated that it is possible to develop and implement different nanoparticles by combining SMW to manage reservoir rock wettability and maximize OR from carbonate reservoirs. Thus, this combination as an effective agent could significantly increase reservoir sweep efficiency. Thus, as a result, using the established hybrid technique has distinct advantages over using SMW flooding alone.

Techno ‐economic analysis of Al 2 O 3 / CuO nanofluid applied in various horizontal ground heat exchangers

A ground source heat pump (GSHP) is widely regarded as a promising technology for building heating, ventilation, and air conditioning because of its higher energy efficiency. Nanofluids (NFs) have also received extensive attention due to their excellent heat transfer characteristics. In this paper, CuO/Al2O3 particles mixed with propylene glycol/water (PG/W, volume ratio: 60/40) are applied to GSHPs as a heat transfer medium. The combination of different pipe types and different concentrations of NFs is studied by comparing the coefficient of performances (COPs) and outlet temperatures. The results show that the 2% CuO NF combined with the spiral type offers the best performance with a 28% rise in the outlet temperature in the pipe and an average COP value of 4.6. When the concentration of Al2O3 NF is 2%, the combined effect of the meander type is the best. The optimal combination of CuO (2%) and spiral type is used for economic analysis by comparing with the performance of natural gas boilers, air source pumps, and GSHPs under similar conditions. The levelized cost of heat analysis results indicate that the horizontal GSHP system coupled with NF can maximize heat exchange efficiency and mitigate environmental effects, but the cost is still high as ¥ 1355/MWh ($212.46/MWh).

Design and Analysis for Heat Transfer Through Twisted Tape with Nanoparticles

Different techniques have been used to achieve a high heat transfer rate. Among them, one of the advanced techniques is a suspension of nanoparticles in the base fluids as water and coated with aluminum and titanium. The present work has been carried out on a double pipe heat exchanger with twisted tape insert with twist ratio (y/w = 4 and 6) and thickness (0.8mm) for heat transfer investigation of water to water and nanofluid to water with counter flow arrangement under turbulent flow conditions. The computational fluid dynamic code simulates different concentrations of nanofluid (0.01% to 0.19%) in ANSYS FLUENT R 18.1 software. The overall heat transfer coefficients for all concentrations are measured as a function of the hot and cold stream's mass flow rates. The thermal performance parameter overall heat transfer coefficient is compared for nanofluids with water. The work concludes that there is a good enhancement in heat transfer rate using nanofluid.

Experimental Investigation of Heat Transfer Characteristics of Automobile Radiator using Tio2 Nanofluid Coolant

Abstract: The use of nanoparticle dispersed coolants in automobile radiators improves the heat transfer rate and facilitates overall reduction in size of the radiators. In this study, the heat transfer characteristics of water/propylene glycol based TiO2nanofluid was analyzed experimentally and compared with pure water and water/propylene glycol mixture. Two different concentrations of nano fluids were prepared by adding 0.1 vol. %, 0.2 vol. %, 0.3 vol. % and 0.4 vol. % of TiO2 nanoparticles into water/propylene glycol mixture (60:40). The experiments were conducted by varying the coolant flow rate between 3 to 6 lit./min. for various coolant temperatures (50°C, 60°C, 70°C, and 80°C) to understand the effect of coolant flow rate on heat transfer. The results showed that the Nusselt number of the Nano fluid coolant increases with increase in flow rate. At low inlet coolant temperature the water/propylene glycol mixture showed higher heat transfer rate when compared with Nano fluid coolant. However at higher operating temperature and higher coolant flow rate, 0.3 vol. % of TiO2nanofluid enhances the heat transfer rate by 8.5% when compared to base fluids. Keywords: Heat transfer enhancement, Propylene Glycol, Radiator, TiO2Nanofluid coolant

Effect of metal oxide nanofluids on the performance of passive solar still single slope for two different absorbent plates

This study aims to improve the performances of a solar still single slope using metal oxide nanofluid (Al2O3–water, Cu2O–water, and TiO2–water). The numerical study was carried out for the climatic conditions of Agadir, Morocco, with different concentrations of nanofluids inside a basin equipped with an absorber plate with two different absorptivities. The numerical study is based on thermal balance equations applied on different solar system components and solved using the Runge Kutta method. The numerical model is validated by comparing our results with the literature available data. A comparison study of the effect of these nanofluids on solar still productivity is done. The results show that the productivity of the solar still using nanoparticles Cu2O, TiO2, and Al2O3 are 7.38, 7.1, and 7.064 kg m−2 day−1, respectively. It is obtained that the maximum efficiency of the solar still is found to be 55.27% by using cuprous oxide nanoparticles. Furthermore, an enhancement in solar still productivity of 6.36%, 19.54%, and 33.25% is obtained by dispersing 1%, 3%, and 5% volume fraction of Cu2O nanoparticles in pure water, respectively compared to the conventional solar. Moreover, the impact of the absorptivity of the absorber plate on the solar still effectiveness is investigated. Two types of coatings are considered to change the absorber plate absorptivity. The results indicate that the efficiencies of the solar system are 58.81% and 51.77% using an absorber plate with 0.95 and 0.85 of absorptivity, respectively.

Sequestration and Storage of Carbon Dioxide Using Hydrate Formation Method in the Presence of Copper Oxide Nanoparticles

The nanofluid-based gas hydrate formation process employing copper oxide (CuO) nanoparticles have been experimentally investigated in this work. Different concentrations of nanofluids are injected into the reactor at the operating condition of 29 bar, 274.15 K, and impeller speed of 100 rpm. It was observed that the kinetics of the carbon dioxide hydrate formation process was greatly affected by the nanoparticles. The remarkable point was that at a very low concentration of 20 ppm, a considerable improvement on the carbon dioxide hydrate formation kinetic without using any surfactant was obtained. At the concentration of 20 ppm, the values of the initial rate of hydrate formation, growth time, and induction time were 0.0495, 194.5, and 4.4 min, respectively, which these results can be of great importance for the use of carbon dioxide hydrate in various industries. The results indicated that the kinetics of gas hydrate formation was also severely influenced by the impeller speed and initial gas pressure. The rate of CO2 captured in the hydrate crystalline lattice is also modeled by the first-order kinetic model. It was seen that this model can be used to predict the rate of hydrate formation with considerable accuracy.

Experimental investigation on thermal conductivity and stability of water-graphite nanofluid

Enhanced thermal conductivity of nanofluids has proven importance in enhancing heat transfer for many application. In this study, thermal conductivity of graphite nanopowder dispersed in water at different temperatures was studied experimentally. Stable nanofluids of different concentrations (0.2 vol%, 0.5 vol%, 0.8 vol%, 1 vol% and 1.5 vol%) are prepared using ultrasonic cleaner by sonicating for 3 hour. Thermal conductivity was measured from temperature 25 to 55 ºC with an interval of 5 ºC using KD2 Pro thermal properties analyser. Experimental results showed that thermal conductivity increases with increase in temperature and volume concentration. Thermal conductivity of Water – Graphite nanofluid showed enhancement of 5.6% to 20.42% for 0.2 vol% to 1.5 vol% of concentration at 25 ºC respectively. However, the maximum improvement of 39.72% was found at 1.5% of concentration at 55 ºC compared to water. A correlation was developed considering the effect of temperature and concentration using the regression method. The proposed correlation effectively predicts the thermal conductivity of Water – Graphite nanofluids with an accuracy of ±2.8%.

Study on viscosity of MWCNT dispersed in ethylene glycol at different operating conditions for thermal applications

In recent times the development of nanotechnology has taken place at an unprecedented rate. Nano-fluids are one of the remarkable outcomes of the development of new technologies that can be used to increase the efficiency of thermal systems. Nanofluids, which consist of particles in nanometre size and a base fluid, have been hailed as a superior alternative compared to a common heat transfer fluid like water due to their better thermal properties and having many potential applications in many fields, especially in HVAC, electronic cooling, solar heating and cooling etc., The MWCNT-based nanofluid with water-ethylene glycol as base fluid is prepared by two-step method, the water and ethylene glycol are mixed in the ratio 80:20 and four different concentrations of nanofluids: 0% wt, 0.015% wt, 0.15% wt, 1.5% wt are prepared. Rheology analysis are made by using rheometer with temperature ranging from from 10° C to 50° C with steps of 10° C and shear rate was controlled with shear stress varying from 0-10 N/m2. The base fluid shows the Newtonian behaviour being shifted to Non-Newtonian Behaviour, specifically shear thinning behaviour. Rate of change of shear also changes with change in temperature and change in shear stress results change in viscosity with higher concentration of nanoparticles showing higher viscosity.

Theoretical Study of Mixed Convection Cooling of Microprocessor Using CuO Nanofluid. (Dept. M)

Cooling of electronic equipments is playing an important role in the last decades as a world experiences a technological boom in all fields. In this study, a numerical study for mixed convection cooling of microprocessor is investigated by the use of pure water and CuO-water nanofluid at six different volume concentrations. The model is built, meshed and simulated by Ansys Fluent Package 16.0 and a mesh independence test is carried out. The study is performed by changing heat load (115W, 130W), inlet velocity, at different concentrations of nanofluids (Pure water, 0.5%, 0.86%, 1.5%, 2.25%, 3.5%, 5%). The present results showed that using CuO-water nanofluids over pure water provides an enhancement in heat transfer characteristics. The dimensionless parameters such as Nusselt number, Archimedes number, Prandtl number, friction factor and dimensionless temperature are studied and correlated. An enhancement of 36.5% in thermal hydraulic performance is found at 0.50% volume fraction at Re = 1679.212. The data are correlated with maximum error of 4.1%.

Heat and Fluid Flow in a Tube with Helical Tape around Rod (Dept.M)

Forced convective heat transfer and friction factor for nanofluid flows inside circular horizontal tube with inserting helical tape, is experimentally studied. Electric heater is wrapped around the outer surface of the tube to obtain a constant and uniform heat flux at the tube wall. Experiments are conducted with adding nano-particles (Al2O3) to water up to 0.35% by volume to obtain different concentrations of nanofluids. An experimental test loop equipped with the required measuring instruments was designed and constructed to assess the effects of nano-particles concentration, mass flow rate, and applied heat flux on the convection heat transfer process and pressure drop. The tested tube fitted with screw helical tape inserts to evaluate its effects on heat transfer rate and friction factor with nanofluid and pure water as a working fluid. The measurements of temperature, flow rate, applied volt and pressure drop are recorded and manipulated to calculate the convective heat transfer coefficient and friction factor. The obtained experimental results show that, wall temp erature is reduced by using nanofluid compared with pure water. Accordingly, the convection heat transfer coefficient increased when using nanofluid and it also increased with increasing heat flux and mass flow rate (Reynolds number). Higher rates of heat transfer and pressure drop are obtained from the tube fitted with screw helical tape insert compared to flow in a plain tube under similar conditions. This imp rovement in the convection heat transfer coefficient characterized by a swirling flow as a result of the secondary flow of the fluid flow inside tube with helical tape and the area of the tape inserted. The average value for the thermal hydraulic performance (ŋ) for tube with inserting helical tape was 1.4 for water only, and 1.8 for nanofluid at concentration 0.2%. Comparison with the previous work shows fairly agreement. A correlation is obtained between Nusselt number and op erating parameter.