Heat Transfer Of Al2O3 Nanofluid Research Articles

Experimental investigation of heat transfer performance of Al2O3 nanofluids in a compact plate heat exchanger

• Heat transfer of Al2O3 nanofluids in compact plate heat exchanger is investigated. • Stability of Al2O3 nanofluids is evaluated. • Thermophysical properties of Al2O3 nanofluids are characterized. • Energy performance and heat transfer enhancement are demonstrated. • Al2O3 nanofluids showed great promises for applications in thermal management systems. This study experimentally investigates the performance of a compact gasketed plate heat exchanger (PHE) employing Al 2 O 3 nanofluids prepared for several low concentrations of Al 2 O 3 (0.01, 0.05, 0.10, 0.15 and 0.20 vol.%) and base fluids of distilled water (DW) and its mixture with ethylene glycol (15% and 30% of EG) for several flow rates (0.03-0.093 l/s). The main thermophysical properties of those nanofluid samples were experimentally measured. The prepared nanofluids samples showed a Newtonian rheological behaviour and an increase in viscosity up to 7.5% for 0.2 vol.%. The enhancements in the thermal conductivity were significant and the values were 7.3 %, 8.4% and 9.1% for Al 2 O 3 nanofluids at 0.2 vol.% compared to the base fluids DW, 15% EG and 30% EG, respectively. A newly developed experimental setup is used to operate the nanofluids through the PHE under particular conditions for heating purposes (mainly high temperature), and their performance is evaluated in comparison with the conventional heat transfer fluids (the base fluids). Nusselt number, pressure drop, and energy efficiency factor were determined for the nanofluids and base fluids. The results indicated a heat transfer enhancement with the increase of the particles’ concentration reached the maximum value of 27% at 0.2 vol.% for DW based Al 2 O 3 nanofluid and was accompanied by an increase in pressure drop of 8%. The heat transfer enhancement became lower with the increase of the EG percentage such as 19.1% at 0.2 vol.% for 30% of EG based Al 2 O 3 nanofluid based. In addition, the energy efficiency factor increased by the addition of Al 2 O 3 nanoparticles to the base fluids and with the increase of flow rates up to the value of 1.3 at the highest particles concentrations. This work provides an important step concerning the performance of particular design of Al 2 O 3 nanofluids and operation conditions in compact PHEs on the road to the development of thermal management systems under the current industry’s trends for optimizing energy use and minimizing equipment.

THERMAL-HYDRAULIC PERFORMANCE OF Al2O3 NANOFLUIDS UNDER LAMINAR FLOW IN A MINITUBE

The improvement of performance and applications that include the convection heat transfer process is extremely related to the thermophysical properties of the fluids. However, it was found that adding nanoparticles to the conventional fluids (known as nanofluids) is an advanced way to enhance their thermophysical properties leading to an enhanced heat transfer process. This study presents a numerical approach to investigate the laminar flow-based convective heat transfer of Al2O3 nanofluids in a mini-tube under constant heat flux boundary conditions (15 kW/m2) and at an inlet temperature of 25°C. For this study, the nanofluid samples are prepared for several concentrations of Al2O3 nanoparticles and ethylene glycol/water mixture as a base fluid. Also, the thermal properties of nanofluids and base fluid are characterized. Computational fluid dynamics tools are used to develop a numerical model and validate it in comparison to experimental data. The results are discussed based on the heat transfer coefficient, considering the entrance area, pressure drop, and friction factor to determine the performance of nanofluids in comparison to the base fluid. A considerable enhancement in the heat transfer, especially in the entrance area up to 17.8%, with a corresponding increase in the pressures drop, friction factor, and the required pumping power of the nanofluids was observed.

Experimental investigation of heat transfer of Al2O3 nanofluid in a microchannel heat sink

Microchannel heat sink (MCHS) with nanofluids has been widely utilized to improve heat transfer performance in micro-scale mechanical systems. Although various studies have demonstrated the heat transfer phenomena of Al2O3 nanofluid in MCHS, the flow and heat transfer characteristics have not been fully elucidated due to a insufficiency of experimental results. To investigate these heat transfer phenomena, measurements of the temperature and velocity fields in the MCHS are important because the flow characteristics influence the heat transfer performance. Therefore, in the present study, velocity and temperature fields of Al2O3 nanofluid and deionized(DI) water in a MCHS were systematically analyzed by employing the particle image velocimetry(PIV) and laser induced fluorescence(LIF) measurement techniques. The heat transfer characteristics were explained using flow behaviors and temperature distribution in the MCHS. Moreover, the entropy generation rate in the MCHS was also evaluated to demonstrate heat transfer performance. When the nanofluid was used as a working fluid in the MCHS, the generation rate of thermal entropy was 6.3% smaller than that of water. In conclusion, we experimentally demonstrated the heat transfer of nanofluid by using the velocity and temperature measurement technique. The results of this study will advance the study of heat transfer using Al2O3 nanofluids.

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.

Two- and three-dimensional comparative study of heat transfer and pressure drop characteristics of nanofluids flow through a ventilated cubic cavity (part I: Newtonian nanofluids)

Through this paper, three-dimensional fluid flow and heat transfer of Al2O3 nanofluid within ventilated enclosures was taken into consideration. Crossed by the nanofluid, the ventilation system is assured by two equivalent openings located at the vertical walls. So, the cold nanofluid gets enter using the opening located at the top of the left side and leaving by the second one, which is located at the bottom of the right side. Except the adiabatic rear and front sides, all parts of the cubic space are maintained at a constant temperature, higher than that of the entrance nanofluid. To make clear the impact of main parameters such as Reynolds number, the Richardson number and nanoparticles volume fraction as well as the 2D extension, the convection phenomenon was reported by means of streamlines and isotherm plots, side by side with the velocity profiles. The main results obtained show that when the Reynolds number increases, the heat exchange rate is an increasing function and the pressure drop is a decreasing function. In addition, in a conductive dominant regime for low Reynolds numbers, the two-dimensional (2D) is valid and can predict the studied phenomena in three-dimensional (3D). Finally, a correlation for the pressure drop is obtained in polynomial form.

Numerical studies on convective heat transfer of Al2O3 nanofluid in circular pipe

A numerical investigation is carried out applying a two phase approach on convective heat transfer of Al2O3 nanofluid flowing through a circular pipe. Five different Reynolds-averaged Navier-Stokes (RANS) turbulence models are employed by using the ANSYS-CFX® code. The analyses are performed for five different Reynolds number and three particle volume fractions. The results show that ω based models give very close results in themselves and that these models show better performance than e based models. SST k-ω model’s predictions are slightly better than those of other ω based models. The performance of this model increases with a decreasing particle volume fraction. It is clearly seen that a two phase approach gives satisfactory results when it is used with ω based models.

Taguchi optimization for natural convection heat transfer of Al2O3 nanofluid in a partially heated cavity using LBM

In the present study for the first time, Taguchi approach was applied to specify the optimal condition of the parameters in the natural convection heat transfer of Al2O3 nanofluid for a partially heated cavity. The flow and energy equations are solved by the lattice Boltzmann method. The influence of the 5 factors including Rayleigh number, position, hot length, cold length, volume concentration of the Al2O3 nanoparticles is examined. The Nusselt number on the hot section is measured for the response factor. In Taguchi optimization method, the levels of every factor were fixed at 3 levels and the L27 orthogonal array. The conclusions of the Taguchi–LBM technique indicated that the optimum conditions were attained at the maximum Rayleigh number, cold length and volume fraction and the minimum hot length in the bottom–bottom configuration in the variety of the design parameters. Also, the most significant parameter influencing the Nusselt number on the hot wall was the Rayleigh number, while changing the volume fraction had a negligible effect.

Lattice Boltzmann Simulation of Mixed Convection Heat Transfer in a Lid-Driven Square Cavity Filled With Nanofluid: A Revisit

Mixed convection heat transfer of Al2O3 nanofluid in a lid-driven square cavity with differentially heated vertical walls is studied numerically with lattice Boltzmann method (LBM). In order to understand the reasons for the conflicting results on heat transfer enhancement in cavity problems, formulation of nondimensional properties and modeling thermophysical properties, in accordance with the relative effects of natural and forced convection flows, are examined. In addition to gain more insight into the physics, one of the goals of the study is to identify the reasons of existing contradictory findings; therefore, a single-phase formulation is adopted as has been the case in the majority of related literature to date. To isolate the effects of thermophysical properties on the results and to maintain the same natural and forced convection effects, all nondimensional parameters are defined using the corresponding thermophysical properties of the fluid under examination. Two different effective thermal conductivity and viscosity models are tested for a range of Reynolds and Rayleigh numbers to investigate their effects on the nanofluid behavior. Depending on the effective viscosity model, an increase or decrease is obtained in the average Nusselt number. It is also illustrated that the relative magnitudes of effective thermal conductivity values for different models do not translate into the heat transfer enhancement due to convective effects. Moreover, it is shown that thermal behavior of nanofluid approaches to the one of base fluid's as the buoyancy driven flow gets stronger, which is independent of the employed effective property models.

Mixed Convection Heat Transfer of Al2O3 Nanofluid on the Elliptical Shapes: Numerical Study of Irreversibility

Mixed Convection Heat Transfer of Al2O3 Nanofluid on the Elliptical Shapes: Numerical Study of Irreversibility

Convective Heat Transfer of Al2O3 Nanofluids in Porous Media

In this study, the performance of a heat sink embedded with a porous medium and nanofluids as coolants is analyzed experimentally. The nanofluid is a mixture of de-ionized water and nanoscale Al2O3 particles with three different volumetric concentrations: ζ = 0.41%, 0.58%, and 0.83%. The experimental test section is a rectangular minichannel filled with metal foam, which is electrically heated to provide a constant heat flux. The porous medium is assumed to be homogeneous and the flow regime is laminar. The result of heat transfer enhancement by slurry of Al2O3 nanofluid in porous media is studied under various flow velocities, heat flux, porous media structure, and particle concentration of nanofluid. The effect of particles volume fraction on heat transfer coefficient is also studied. This experimental study discovers and/or confirms the following hypotheses: (1) nanoparticle slurry in conjunction with metal foam has a significant effect on heat transfer rate; (2) there is an optimum permeability for the foam resulting in maximal heat transfer rate; (3) for a fixed particle concentration, smaller particles are more effective in enhancing heat transfer; and (4) increasing particle concentration results in some gains, but this trend weakens after a threshold.

Force convection heat transfer of Al2O3 nanofluids for different based ratio of water: Ethylene glycol mixture

Nanofluids are developed to meet the challenges of improving the efficiency of the cooling system subsequently minimizing the energy waste. This paper aims to investigate the forced convection heat transfer for Al2O3 nanofluids in different based ratio of water (W) and ethylene glycol (EG) mixture. The Al2O3 nanofluids are formulated using the two-step method for three based mixture ratio of 60:40, 50:50 and 40:60 (W:EG) by volume. The forced convection experiments are conducted under constant heat flux conditions for operating temperatures of 30–70°C and Reynolds numbers of 3000–25,000. The heat transfer coefficient of nanofluids is enhanced with concentration compare to its base fluid at all designated temperature. It is observed to be improved further with the increase of temperature. The effect of different base mixture ratio display that nanofluids in 60:40 base mixture have the highest percentage of performance with 24.6% enhancement at 1.0% concentration and temperature of 70°C. The increment of concentration for nanofluids shows a slight rise in friction factor. As a conclusion, the thermo-physical properties and the forced convection heat transfer for nanofluids in various base mixture is significantly influenced by concentration, temperature and base ratio of mixture.

Natural Convection Heat Transfer of Al2O3 Nanofluid Through Packed Beds

Natural Convection Heat Transfer of Al2O3 Nanofluid Through Packed Beds

Experimental investigation on enhancement of heat transfer using Al2O3/water nanofluid in a u-tube with twisted tape inserts

An investigation is made experimentally with an attempt to enhance the rate of heat transfer of Al2O3 nanofluid in a U-tube heat exchanger with twisted tape insert. The heat transfer coefficients and the corresponding friction factors needed for performance analysis are determined at variable operating conditions of the heat exchangers with particle volume concentration of 0.01% and 0.03% and twist ratios ranging between 5 and 20. Experimental data are obtained at flow rates ranging from 0.0333 to 0.2667kg/s and Reynolds number ranging from 3000 to 30,000. The Nusselt number of entire pipes for 0.03% concentrations of nanofluid with twisted tape inserts is enhanced by 31.28% compared to water while the friction factor is increased by 1.23 times compared to water with twisted tape insert of H/D=5. Correlations are developed to estimate the Nusselt number and friction factor. The results of the investigation indicated significant improvement in the performance parameters of the heat exchanger with a rise in volume concentration of the nanoparticle.

A comprehensive comparison of various CFD models for convective heat transfer of Al2O3 nanofluid inside a heated tube

This study presents a comprehensive comparison between various models in numerical/CFD approaches to investigate a case study of the laminar forced convection flow of Al2O3/water nanofluid with 1.6% volume fraction and Re=1600 in a heated tube. The quantitative deviation in Nusselt number for the case study is reported using (i) four types of single-phase models, including Newtonian and non-Newtonian single-phase models with assessing the effect of two different thermal dispersion models based on velocity and temperature gradient (ii) four types of two-phase models, including Eulerian, mixture (types 1 and 2) and discrete phase models. According to the results, non-Newtonian single-phase model predicts more accurate Nusselt number than Newtonian single-phase model, with average errors of 5.98% and 4.84% respectively. Incorporating the dispersion models in non-Newtonian single-phase approach, the average error decreases to 2.07% for dispersion models type 1 and 3.33%, for dispersion models type 2. Regarding two-phase models, Eulerian, mixture type 1, mixture type 2, and discrete phase model show the average error of 2.79%, 17.57%, 5.87% and 2.73% respectively. The repeatability and the consistency of the findings of some of most accurate models was checked for 0–2% nanoparticle volume fraction and also for Re ranging from 745 to 1600. This study benefits when comes to selecting a suitable model for a similar type case study.