TiO2-H2O Nanofluids Research Articles

Analysis of thermal performance and irreversibility of double-diffusive buoyancy-driven nano-suspension subject to local thermal non-equilibrium model

In fact, local thermal equilibrium (LTE) would be unsuitable when it comes to nuclear reactors, electronic equipment, space devices, geothermal engineering, and high-conductivity foams, due to prominent temperature discrepancy between the two constituents (solid and nanofluid) in porous material. Local thermal non-equilibrium (LTNE) situation may be considered in above real world applications. In view of above relevance, the effects of LTNE model on double-diffusive natural convection (DDNC) within a fluid-saturated porous container loaded with the TiO2-H2O nanofluid and emplacing four cooling and hot channels in Forchheimer-Brinkman-extended Darcy medium have been investigated in the present study. The momentum, heat and mass equations are solved by finite element method. Irreversibility in the two constituents (nanofluid and solid) of the porous structure has been analyzed. The significant outcomes are that fluid circulations enhance due to rise in porosity of the medium. Fluid friction entropy EnFF,T ameliorates significantly by 1514.16 % and 872.97 % with increase in Rayleigh number and porosity of the medium. It is clear that Nuloc,nf,Nuave,nf, Nuloc,s&Nuave,s enhance significantly with rise of buoyancy and thermal conductivity ratio, interstitial solid/fluid heat transfer coefficient.

Buoyancy-driven nano-suspension subject to interstitial solid/nanofluid heat transfer coefficient: Role of local thermal non-equilibrium (LTNE)

BackgroundBecause of the prominent temperature discrepancy between fluid and solid in porous material, local thermal equilibrium (LTE) is not suitable in case of high-conductivity foams and electronic equipment. In view of above situation, Darcy-Brinkman-Forchheimer model subject to local thermal non-equilibrium (LTNE) is implemented. LTNE technique finds real world applications include groundwater pollution, geothermal extraction, microwave heating, industrial separation process, and transpiration cooling featuring with porous structure. The present study aims at the investigation of the entropy and hydrothermal characteristics of buoyancy-driven TiO2-H2O nanofluid inside a cross-shaped domain embodying two hot and cold rings influenced by LTNE. MethodsFinite element method (FEM) has been considered to solve the dimensionless form of governing equations. Significant findingsAmplification of interstitial solid/nanofluid heat transfer coefficient accounts for the intensification of streamlines, velocities, and diminution of isothermal lines in both nanofluid and solid matrix phases under the influence of LTNE. Strengthening of medium porosity whittles down entropy due to thermal effects in both nanofluid and solid phases, and that ameliorates entropy due to fluid friction and porous medium irreversibilities. Local and average Nusselt numbers in nanofluid phase reduce by 29.31 %, 20.72 %, 17.16 %, and 14.78 % while that in solid phase decays by 13.18 %, 7.63 %, 4.9 %, and 2.8 % for rise in εfrom 0.1 to 0.3, 0.3 to 0.5, 0.5 to 0.7, and 0.7 to 0.9, respectively. Introduction of Darcy-Brinkman-Forchheimer model subject to LTNE yielded better results in hydrothermal behavior of TiO2-H2O nanofluid inside a cross-shaped domain emplacing two hot and cold rings than earlier published results.

Experimental analysis of convective boiling heat transfer and nanoparticle deposition effect of TiO2-H2O nanofluids in microchannels

The convective boiling heat transfer characteristics of TiO2-H2O nanofluids in microchannels were experimentally investigated in this paper. The effects of the mass flow rate, mass fraction and nanoparticle size on the average flow boiling heat transfer coefficient were examined at heat fluxes of 138.4–220.5 kW/m2. The results have shown that the average flow boiling heat transfer coefficient of TiO2-H2O nanofluids increases with the increase of the mass flow rate and nanoparticle size. When the mass fraction of TiO2-H2O nanofluids ranges from 0.01 % to 0.1 %, the maximum heat transfer efficiency has reached with the mass fraction of 0.025 %. Considering the movement and deposition of the TiO2 nanoparticles in the convective boiling process, the difference of the absorbance value of TiO2-H2O nanofluids and heating surface morphology after boiling were observed. It proved that the distribution density of the nanoparticle deposition gradually increases along the flow direction of the microchannel. Furthermore, the mass fraction of TiO2-H2O has great influence on the nanoparticles deposition morphology and the nucleation condition of the boiling surface.

Thermal performance of dual flow slotted fin mini channel heat sink using Al2O3-H2O and TiO2-H2O: a numerical and experimental approach

To overcome the extensive heat generation inside the microprocessors nanofluids have gained importance because of their better thermophysical properties as compared with air and water. This work proposes a two-pronged strategy for thermal performance enhancement of mini channel heat sinks. Firstly, a novel dual flow slotted fin mini channel heat sink flow configuration is proposed. Secondly, a detailed numerical investigation is performed to assess heat transfer enhancement property of Al2O3-H2O and TiO2-H2O nanofluids. Considering the first step, fin spacing, number of slots, slot thickness and slot angle are investigated in detail yielding to the selection of best structural parameters. Two slots per fin of 0.5 mm thickness at an angle of 45° is selected because it provides better thermal performance as compared with water. Further, numerical assessment of nano fluid behavior was carried out at volumetric concentrations of 0.005% and 0.01%. For the case of novel dual flow slotted fin mini channel heat sink, maximum numerical and experimental advantages in all targeted system properties is observed for Al2O3-H2O nano fluid at volumetric concentration of 0.01%, as compared with water. Al2O3-H2O nano fluid provides better thermal performance both numerically and experimentally as compared with TiO2-H2O nanofluids. Increment in the pressure drop is noted with increasing volumetric concentrations.

Numerical investigation with sensitivity study of MHD mixed convective hexagonal heat exchanger using TiO2–H2O nanofluid

This ongoing study is carried out to analyze the thermal performance with sensitivity study of a mixed convective hexagonal heat exchanger containing TiO2–H2O nanofluid. Magnetic force is regarded to be horizontal while all surrounding walls are adiabatic. The finite element method is used to simulate the regulatory equations. For the first time, response surface methodology is used to analyze the sensitivity of independent factors on a hexagonal heat exchanger. The findings are depicted for four parameters, Reynolds number (10 ≤ Re ≤ 200), Richardson number (0.01 ≤ Ri ≤ 10), Hartmann number (0 ≤ Ha ≤ 100), and nanoparticle volume fraction (0 ≤ φ ≤ 0.1) against velocity distribution, average Nusselt number (Nuav), streamlines, isotherm lines, and heatlines. The results indicate that the growing value of Re and φ strengthen the thermal performance of nanofluid whereas increasing Ha causes it to decrease. Moreover, φ and Re have positive sensitivity to the Nuav while Ha has negative sensitivity. When Ha is maintained at 0, the optimal value of Nuav reaches when Re = 200 and φ = 0.1. The use of TiO2–H2O nanofluid improves the water's heat transmission ability to 17.69%. Finally, the results of this study may offer advice for creating an effective mixed convective heat exchanger.

Performance investigation of an all glass evacuated tube solar collector with an innovative heat exchanger design using TiO2-H2O nanofluids- an experimental study

ABSTRACT The objective of the current study is to experimentally analyze the thermal performance of an all-glass evacuated tube solar collector (ETSC) with an innovative heat exchanger design by employing TiO2-H2O nanofluid as a heat transmission fluid. Different higher volume concentration (v/c) of TiO2 nanoparticles, i.e. 0.83%, 0.9%, and 0.94% are examined to explore the impact of the nanofluids on the ETSC performance in comparison with only water based ETSC. An outdoor experimental investigation has been carried out using nanofluid at 0.6, 0.7 and 0.8 l/min volumetric rates of flow and its impact using serpentine copper tube coil having uniform pitch distance of 14.3 cm with aluminum fins attached on both side of coil having diameter 12 mm and thickness 1 mm, respectively. The study indicates that thermal performance of ETSC increases with the rise in volumetric flow rate with higher v/c of nanoparticles. For this condition, the temperature rise of water using nanofluid is higher than simple water-based ETSC system, recording an increase in outlet temperature by 4.21%. The maximum thermal efficiency obtained is 52.33% at 0.9% v/c and 0.8 l/min. A comparative assessment between the obtained results and some of the published results reveals that by using serpentine copper coil attached with aluminum fins, with higher concentrations of TiO2 nanoparticles and maintaining higher volumetric flow rate, thermal efficiency of ETSC can be much improved.

Effects of metal foam filling heights and tilt angles on the cooling performance of a heat sink filled with nanofluids

To enhance the cooling performance of heat sink in the field of thermal management of electronic components, a novel heat exchanger system with different filling heights and tilt angles was proposed in this study. TiO2-H2O nanofluids (ω = 0.3 wt%) were selected as the cooling medium, and porous media metal foam (copper, ε = 90%, PPI = 30) was chosen as the enhanced heat dissipation structure. The effects of the different filling heights (H = 2 mm, 4 mm, 6 mm, 8 mm), different tilt angles (θ = 0°, 30°, 60°, 90°) on the cooling performance of nanofluids in a heat sink were studied experimentally, and a comprehensive performance evaluation criterion (PEC) was adopted to analyze the comprehensive performance of heat sink. Research outcomes showed that metal foam with filling height H = 6 mm instead of the highest filling height shows the best comprehensive performance, and the comprehensive performance firstly increases and then decreases with the increase of the filling height. Increasing tilt angle of heat sink is disadvantage to the cooling performance, and heat sink with a tilt angle of θ = 0° shows the best comprehensive performance. The results of this paper provide some reference for the application of nanofluids and porous media in the field of thermal management of electronic components.

Convective flow of a Williamson hybrid nanofluid in a porous medium through a cone and wedge with the effect of the shape of nanoparticles

AbstractThe performance of nanofluid in the heat transport phenomena showed satisfactory results, which have been considered by scientists and researchers. The dispersion of two nanoparticles to form a mixture which named as hybrid nanofluid. It has been proved experimentally that hybrid nanofluid has good thermal performance compared to unitary nanofluid. The present study inspected the convective flow of a Williamson hybrid nanofluid through a cone and wedge in a porous medium of different shapes of nanoparticles (cylindrical‐, spherical‐, blades‐, platelets‐, bricks‐) under the influence of a magnetic field. The partial differential equations were converted to an ordinary differential equation and the resulting equations were solved using the bvp4c MATLAB code. The effect of some important physical parameters on both the velocity and temperature profile was graphically plotted and the effect of the shape and size of nanoparticles was discussed, the numerical values of the friction coefficient and Nusselt number were obtained. As observed, the friction factor of Ag–TiO2–H2O hybrid nanofluid was more than that of TiO2–H2O nanofluid. A significant enhancement in bulk temperature is seen for the Ag–TiO2 hybrid and nanofluid formed by blade‐shaped nanoparticles followed by cylindrical, platelet, brick, and spherical nanoparticles. In addition, for a 5% volume fraction of using blade nanoparticles shape givean increase in skin friction factor about 4.8% compared tobrick hybrid nanoparticles. A comparative study of different forms for Ag‐TiO2was presented graphically.

Theoretical Analysis of Cu-H2O, Al2O3-H2O, and TiO2-H2O Nanofluid Flow Past a Rotating Disk with Velocity Slip and Convective Conditions

The nanofluids can be used in the subsequent precise areas like chemical nanofluids, environmental nanofluids, heat transfer nanofluids, pharmaceutical nanofluids, drug delivery nanofluids, and process/extraction nanofluids. In short, the number of engineering and industrial applications of nanofluid technologies, as well as their emphasis on particular industrial applications, has been increased recently. Therefore, this exploration is carried out to analyze the nanofluid flow past a rotating disk with velocity slip and convective conditions. The water-based spherical-shaped nanoparticles of copper, alumina, and titanium have been considered in this analysis. The modeled problem has been solved with the help of homotopic technique. Convergence of the homotopic technique is shown with the help of the figure. The role of the physical factors on radial and tangential velocities, temperature, surface drag force, and heat transfer rate are displayed through figures and tables. The outcomes demonstrate that the surface drag force of the water-based spherical-shaped nanoparticles of Cu, Al2O3, and TiO2 has been reduced with a greater magnetic field. The radial and tangential velocities of the water-based spherical-shaped nanoparticles of Cu, Al2O3, and TiO2, and pure water have been augmented via magnetic parameter. The radial velocity of the water-based spherical-shaped nanoparticle of Cu has been augmented via nanoparticle volume fraction, whereas reduced for the Al2O3 and TiO2 nanoparticles. The tangential velocity of the water-based spherical-shaped nanoparticles of Cu, Al2O3, and TiO2 has reduced via nanoparticle volume fraction. Also, the variations in radial and tangential velocities are greater for slip conditions as compared to no-slip conditions.

Numerical analysis of flow and heat characteristic around micro-ribbed tube in heat exchanger system

In order to improve the energy utilization rate, this paper analyzes the flow around the cylinder in the tube-row channel heat exchanger through numerical simulation. Effects of micro-rib structure types (vertical rib and ring rib), number of ribs (N = 0, 4, 6, 8), height of ribs (H = 2, 3, 4 mm), pitch diameter ratio (ST/D = 1.5, 2, 2.5), mass fractions (ω = 0–0.5%) and Reynolds numbers (Re = 514–1205) on the flow and heat transfer characteristics of tube-row channel heat exchangers are analyzed. Results showed that TiO2-H2O nanofluids can improve the comprehensive performance of heat exchanger, and when the mass fraction is 0.4%, the tube-row channel heat exchanger has the best performance. For heat exchangers with different types and structural parameters, the adjustment of the number of ribs, the height of ribs, the ratio of transverse pitch diameter and the use of nanofluids can increase Nusselt numbers by 53.63%, 57.25%, 52.38% and 12.93% at maximum, respectively.

Effectively inhibiting particles aggregation and sedimentation for TiO2-H2O suspension by application of an electrode

Inhibiting particles aggregation plays a crucial role in maintaining the stability of nanofluids. In this work, applying a rod electrode was developed to reduce particles aggregation and sedimentation for TiO2-H2O suspensions. The experimental results show that the aggregation and sedimentation of TiO2 particles are effectively suppressed when a rod electrode is inserted into the TiO2-H2O suspensions due to the increase of the absolute value of particle zeta potential. There is an optimal electric voltage (0.5 kV) to achieve the maximum suppression of sedimentation, while surface flaw of the electrode is harmful to suppress sedimentation. The mechanism for inhibition of sedimentation by the electrode is speculated that the charges transfer between the electrode and the TiO2 nanoparticles by the contact electrification. Therefore, the application of the electrode with the optimal design has great potential for improving the stability of the TiO2-H2O nanofluids.

Performance investigation of a concentric double tube heat exchanger using twisted tape inserts and nanofluid

A horizontal double-tube counter-flow heat exchanger with and without twisted tape inserts (twist ratio of 3.2, 4, and 6) has been investigated experimentally using TiO2-H2O nanofluid. In this study, the heat transfer coefficient and friction factor of turbulent flow of TiO2-H2O nanofluid have been determined for Reynolds’ number varying from 5,000 to 25,000. Convective heat transfer coefficient for TiO2-H2O nanofluid (0.05% by vol.) is found to be higher than base fluid (4–6%). Also, an increase in the heat transfer coefficients up to 6%, 10.9%, 17.4%, and 23.4% are observed numerically for the 0.05%, 1%, 2%, and 3% volume concertation of nanoparticles of TiO2. On the other hand, when TiO2-H2O nanofluid (0.05% by vol.) is investigated using twisted tape inserts of twist ratio 3.2, the heat transfer coefficient is found to be increasing by 45%. The variation of the heat transfer coefficient for different types of nanofluids such as; TiO2-H2O, Al2O3-H2O, and CuO-H2O with 1% concentration of nanoparticles (by vol.) has also been studied at different Reynolds’ numbers. The simulated results show no significant effect of the size (30 nm and 50 nm) of nanoparticles (TiO2) on the heat transfer coefficient values of TiO2-H2O nanofluid at 0.05% volume concentration.

Magnetohydrodynamic Flow and Heat Transfer of TiO2-H2O Nanofluid over Nonlinear Stretching Sheet under the Effects of Nanoparticle Diameter

Magnetohydrodynamic Flow and Heat Transfer of TiO2-H2O Nanofluid over Nonlinear Stretching Sheet under the Effects of Nanoparticle Diameter

Hydro-thermal performance of normal-channel facile heat sink using TiO2-H2O mixture (Rutile–Anatase) nanofluids for microprocessor cooling

Thermal management of microelectronics is a challenging task in modern high heat generating devices. In this work, thermal performance of normal-channel facile heat sink has been investigated using water and TiO2-H2O (mixture of Rutile and Anatase) nanofluids with volumetric concentration of 0.005% and 0.01%. The maximum reduction in base temperature was noted for TiO2-H2O (∅ = 0.01%) and TiO2-H2O (∅ = 0.005%) as 8.2% and 5.5%, respectively, when compared with water. The thermal performance of normal-channel facile heat sink was then compared with the mini-channel integral fin heat sink. The base temperature of normal-channel facile heat sink was found very close to mini-channel integral fin heat sink with a maximum difference of 1.8%. The total cost to fabricate mini-channel heat sink was almost 5.3 times greater than normal-channel heat sink. So, the normal-channel heat sink has economical advantage over the mini-channel heat sink in terms of lower fabrication cost with similar thermal performance. However, the pressure drop was found greater for normal-channel as compared to mini-channel heat sink. The experimental results of normal-channel facile heat sink were also validated numerically, and a good agreement was found.

Natural convection heat transfer characteristics of TiO2–H2O nanofluids in a cavity filled with metal foam

In this paper, TiO2–H2O nanofluids are used instead of traditional mediums such as water and oil as the heat transfer medium. For the purpose of research on the natural convection heat transfer characteristics of TiO2–H2O nanofluids in a cavity filled with metal foam, a natural convection experiment system filled with different pore density (PPI) copper foam was established. The experimental results showed that the filling of the metal foam greatly improves the heat transfer effect in the cavity. When the PPI of the metal foam copper is 5 and 25, the Nusselt numbers are similar and larger than that of PPI = 15. The heat transfer effect of water in a cavity with the PPI = 5, PPI = 15 and PPI = 25 metal foam can be enhanced by 58.8%, 31.4% and 63.3% compared with that without metal foam, respectively. The heat transfer effect increases with the concentration of nanofluids. TiO2–H2O nanofluids with 0.1%, 0.3% and 0.5% mass fraction can enhance heat exchange by 6.3%, 22.9% and 32.1% compared with water, respectively. In addition, as the heating power increases, the heat transfer is improved while the heat transfer enhancement efficiency deteriorates.

RETRACTED: MRT lattice Boltzmann simulation of free convection in a symmetrical annulus combined with experimental data of TiO2-H2O nanofluid's properties

Abstract The axisymmetric nanofluid flow and heat transfer in a two-dimensional vertical annulus are investigated. The Multi-Relaxation-Time lattice Boltzmann model is used to simulate the flow and temperature fields. Hence, the macro cylindrical energy equation is exactly recovered using Chapman-Enskog analysis. The numerical results of the present numerical approach are compared with those existed researches, and it is found that there are close agreements between the results. In addition, the thermo-physical properties of TiO2-H2O nanofluid are measured in the laboratory. The Rayleigh number, nanoparticle concentration of nanofluid and aspect ratio of annulus are governing parameters. It is found that the maximum enhancement of average Nusselt number are about 45% and 94%, respectively; when the volume fraction of nanofluid and Rayleigh number change from their minimum values to maximum values. On the other hand, the maximum increment of total entropy generation is about 57% as the Rayleigh number enhances.

Experimental study on the flow and heat transfer characteristics of nanofluids in double-tube heat exchangers based on thermal efficiency assessment

Thermal performance and pressure drop of TiO2-H2O nanofluids in double-tube heat exchangers are investigated. The influence of the thermal fluid (water) volume flow rates (qv = 1–5 L/min), nanoparticle mass frictions (ω = 0.0%, 0.1%, 0.3% and 0.5%), nanofluids locations (shell-side and tube-side), Reynolds numbers of nanofluids (Re = 3000–12000), and the structures of inner tubes (smooth tube and corrugated tube) is analyzed. Results indicate that nanofluids (ω = 0.1%, 0.3% and 0.5%) can improve the heat transfer rate by 10.8%, 13.4% and 14.8% at best compared with deionized water respectively, and the number of transfer units (NTU) and effectiveness are all improved. The pressure drop can be increased by 51.9% (tube-side) and 40.7% (shell-side) at best under the condition of using both nanofluids and corrugated inner tube. When the nanofluids flow in the shell-side of the corrugated double-tube heat exchanger, the comprehensive performance of nanofluids-side is better than that of the smooth double-tube heat exchanger.

Experimental investigation on heat transfer characteristic of TiO2-H2O nanofluid in microchannel for thermal energy storage

In order to enhance the heat transfer performance of phase change material (PCM) for thermal energy storage (TES) in tiny devices, such as battery thermal management, light-emitting diode and electronic device cooling, TiO2-H2O nanofluids and the microchannel were combined in this paper. Two crystal forms of TiO2-H2O nanofluids were prepared by using a two-step method. And paraffin was used as PCM. The stability and thermophysical properties of the above two nanofluids were tested and compared. It can be found that R TiO2-H2O nanofluid has better stability, and its thermal conductivity increases maximally by 3.27%, while the value is 2.88% of A TiO2-H2O. Besides, R TiO2-H2O nanofluid increases the viscosity by a maximum of 4.87%, while A TiO2-H2O increases by 7.45%. Considering these properties, R TiO2-H2O nanofluid was chosen to study the heat transfer characteristics in the microchannel within a TES unit. The results indicate that R TiO2-H2O nanofluid with 1.0 wt% increases Nu by 19 ∼ 41% and 6 ∼ 14% during the melting process and solidification process respectively. In addition, the melting time of paraffin decreases by a maximum of 32.90% and the solidifying time of paraffin decreases by a maximum of 22.57%. During the whole TES process, there is an increase in pressure drop of no more than 8%.

Influence of triangle tube structure with twisted tape on the thermo-hydraulic performance of nanofluids in heat-exchange system based on thermal and exergy efficiency

An experiment is carried out to research the thermo-hydraulic performance of TiO2-H2O nanofluids in triangle tubes while taking the effect of twisted tapes into consideration. The theories of thermal and exergy efficiency are applied to estimate this system. The influence of mass fractions of nanoparticles (0.1 wt%, 0.3 wt% and 0.5 wt%), Reynolds numbers (Re = 800–9000), different structures of triangle tubes (isosceles right triangle tube (tube 1), isosceles 45° triangle tube (tube 2)) and twisted tape on the Nusselt number, Nusselt number ratio, resistance coefficient, resistance coefficient ratio and pressure drop are experimentally studied respectively. Results show that there are three positive factors for heat transfer performance including large nanoparticles concentration, large Reynolds number and existence of the twisted tape. Compared with the smooth tube, tubes (tubes 1 and 2) with twisted tape can enhance heat transfer, but that without twisted tape can deteriorate heat transfer, for heat transfer performance, tube 2 is better than tube 1. Tube 2 with twisted tape has the biggest value of comprehensive performance index R3. A better exergy efficiency performance can be obtained when Reynolds number is greater than 5000 and the exergy efficiency reaches the best when Re = 8000.

Effect of corrugation pitch on thermo-hydraulic performance of nanofluids in corrugated tubes of heat exchanger system based on exergy efficiency

In this article, water and TiO2-H2O nanofluids are used as heat exchange mediums. The heat transfer and resistance coefficient of corrugated tubes with different corrugation pitches are studied by experimental method. The economy of experimental system is evaluated from the aspects of quantity and quality of energy by thermal and exergy efficiencies respectively. The heat transfer performance of nanofluids in the smooth tube can be enhanced by 2.64–16.9% compared with water under the same working conditions, while the corrugated tubes can improve the heat transfer performance by 4.8–66.3%. When the mass fraction of the nanofluid is 0.5%, the corrugated tubes with different corrugation pitches can increase the heat transfer by 36.3% (P = 6 mm), 40.3% (P = 4 mm) and 44.5% (P = 2 mm) respectively. For thermal efficiency, the results prove that when the Reynolds number is larger than 6000, the comprehensive evaluation indexes of corrugated tubes are much larger than that of smooth tube, and the maximum can reach 1.5637. For exergy efficiency, the research results show that the exergy efficiency of the smooth tube is better than that of the corrugated tubes.