Numerical investigation of Al2O3/water nanofluid laminar convective heat transfer through triangular ducts (original) (raw)
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Laminar convective heat transfer of Al2O3/water nanofluid through square cross-sectional duct
International Journal of Heat and Fluid Flow, 2013
The present paper is an experimental study of Al 2 O 3 /water nanofluid convective heat transfer through square cross-sectional duct under constant heat flux in laminar flow. The increase of heat transfer coefficient is one of the most important technical aims for industry and researches. Also, the decrease in the pressure drop for systems that generate high fluid pressure drop is very noticeable. Convective heat transfer can be enhanced passively by changing flow geometry and boundary conditions or by improving the thermal conductivity of the working fluid. A square cross section duct has the advantage of lower pressure drop, but it has a lower heat exchange rate than that of a circular duct and it is expected that using of nanofluid as a new heat transfer media may improved the heat transfer performance of this kind of duct. In this study, convective heat transfer coefficients and Nusselt numbers of nanofluid were obtained for different Al 2 O 3 nanoparticles concentrations as well as Peclet numbers. Experiments show that considerable enhancement of heat transfer coefficient is achieved and this enhancement is up to 27.6% at 2.5% volume fraction of nanoparticles comparing to the base fluid (water), also it has been noticed that convective heat transfer coefficient increases with the increment of nanoparticles' concentration in nanofluid especially at high flow rates. The decrement of wall temperature observed using nanofluid.
Chemical Product and Process Modeling, 2017
This research presents the numerical results of laminar forced convective heat transfer performance and the flow behaviour for Al 2 O 3-water nanofluid in circular, 2:1 rectangular, 4:1 rectangular and square ducts. The nanoparticles concentration studied were 0.01%, 0.09%, 0.13%, 0.25%, 0.51%, 1.00% and 4.00%. Single phase constant and temperature-dependent properties were employed. For the case of constant properties, the thermal performance and pressure drop increase with the increase of nanofluid concentration and Reynolds number. For the temperature-dependent properties, the Nusselt number and pressure drop also increase when the Reynolds number increases. However, there is a slight decrement in the Nusselt number and no significant pressure drop increment when the nanofluid concentration is increased from 0.01% to 1.00%. When the concentration is further increased to 4.00%, the Nusselt number and pressure drop increase. For the temperature-dependent model, lower thermal performance and pressure drop are identified when compared to those of the constant properties. The maximum Nusselt number enhancement and pressure drop increment occur at the concentration of 4.00% and Reynolds number of 2000. They are 25.43% and 945.69% as well as 4.86% and 117.01% for constant and temperature-dependent properties, respectively. The thermal-hydraulic efficiency of nanofluid is found to be not as good as the pure water.
2017
In the present research, the laminar forced convective heat transfer and fluid flow characteristics for Al2O3-water nanofluid flowing in different bend (i.e., 180o and 90o) pipes have been investigated numerically in a three-dimensional computational domain using the finite volume technique. The effects of different pertinent parameters, such as the Reynolds number of the duct, volume fraction of the nanoparticle, the diameter of the nanoparticle, aspect ratio of the duct and the duct bend angle on the hydrodynamic and thermal characteristics of the flow has been presented. It is observed that the heat transfer is augmented by replacing conventional fluid by Al2O3-water nanofluid. The nanoparticle volume fraction is found to be an important parameter to increase the heat transfer in the bend pipe. It is also observed that the thermo-hydraulic characteristics of the flow changes with the duct aspect ratio, and the heat transfer rate is improved with aspect ratio. The heat transfer wi...
2012
In this paper, fully developed laminar and turbulent flow convective heat transfer characteristics of Al2O3/water nanofluid flowing through a uniformly heated horizontal tube with and without wire coil inserts is presented. For this purpose, Al2O3 nanoparticles of 43 nm size were synthesized, characterized and dispersed in distilled water to formulate Al2O3/water nanofluid containing 0.1, 0.15 and 0.2% volume concentration of nanoparticles. Two wire coil inserts made of stainless steel with pitch ratios 2 and 3 were used. The results provide experimental evidence that the mechanism of thermophoresis play a pivotal role in explaining the heat transfer enhancement observed with nanofluids. Keywords— Heat transfer enhancements, Nusselt number, Nanofluid, Wire coil insert.
Heat Transfer-Asian Research, 2012
The present paper focuses on the heat transfer of an equilateral triangular duct by employing the CuO/water nanofluid in a laminar flow and under constant heat flux condition. The triangular ducts were used due to their ease of creation and high compaction. They have less pressure drop when compared to the circular and non-circular ducts and their other attributes are very useful in industrial applications. These reasons cause their heat transfer characteristics to be very important. In this paper, to improve the heat transfer of an equilateral triangular duct, a CuO/water nanofluid was employed. The nanofluid was conducted through an equilateral triangular duct with a constant wall heat flux. Results show that the experimental heat transfer coefficient of the CuO/water nanofluid is more than that of distilled water. Also, the experimental heat transfer coefficient of a CuO/water nanofluid is greater than the theoretical one. The heat transfer enhancement of the equilateral triangular duct increases with the nanofluid volume concentration as well as the Peclet number. So a 41% enhancement in the convective heat transfer coefficient for a 0.8% CuO/water nanofluid can be seen when compared to pure water.
Experimental Thermal and Fluid Science, 2013
This article presents the heat transfer coefficient and friction factor of the nanofluids flowing in a horizontal tube under laminar flow conditions, experimentally. The experiments have been done on fully developed region under the constant wall temperature condition. Al 2 O 3 nanoparticles with diameters of 40 nm dispersed in distilled water with volume concentrations of 0.1-2 vol.% were used as the test fluid. All physical properties of the Al 2 O 3-water nanofluids needed to calculate the pressure drop and the convective heat transfer coefficient have been measured. The results show that the heat transfer coefficient of nanofluid is higher than that of the base fluid and increased with increasing the Reynolds number and particle concentrations. The heat transfer coefficient increases by approximately 32% in the fully developed region at 2 vol.% nanofluid. The measured pressure loss for the nanofluids was in general much higher than for pure water. The experimental results illustrate that the single phase correlation with nanofluids properties could not predict heat transfer coefficient enhancement of nanofluids fairly.
Heat Transfer Asian Research, 2012
The present paper focuses on the heat transfer of an equilateral triangular duct by employing the CuO/water nanofluid in a laminar flow and under constant heat flux condition. The triangular ducts were used due to their ease of creation and high compaction. They have less pressure drop when compared to the circular and non-circular ducts and their other attributes are very useful in industrial applications. These reasons cause their heat transfer characteristics to be very important. In this paper, to improve the heat transfer of an equilateral triangular duct, a CuO/water nanofluid was employed. The nanofluid was conducted through an equilateral triangular duct with a constant wall heat flux. Results show that the experimental heat transfer coefficient of the CuO/water nanofluid is more than that of distilled water. Also, the experimental heat transfer coefficient of a CuO/water nanofluid is greater than the theoretical one. The heat transfer enhancement of the equilateral triangular duct increases with the nanofluid volume concentration as well as the Peclet number. So a 41% enhancement in the convective heat transfer coefficient for a 0.8% CuO/water nanofluid can be seen when compared to pure water.
2007
In this work, an experimental investigation was carried out to study a laminar mixed convection flow and heat transfer of Al2O3-water nanofluid inside a horizontal tube submitted to a uniform wall heat flux at its outer surface. Measured data were collected for the following ranges of the governing parameters: the Reynolds number between 170 and 630, the Grashof number between 1.5 10 and 9.2 10 and the Prandtl number between 7 and 7.42. Results have shown that the experimental heat transfer coefficient remains nearly constant with an increase of particle volume concentration from 0 to 2%. However, we have observed a slight decrease of the Nusselt number with an increase of the particle volume fraction from 0 to 2%. Key-Words: Heat transfer, Laminar flow, Mixed convection, Natural and forced convection, Nanofluid, Al2O3-Water mixture, Alumina nanoparticles, Experimental study.
Asian Review of Mechanical Engineering
A numerical investigation was conducted to predict the greater thermal enhancement in the rectangular duct using different nanofluids – Aluminum oxide (Al2 O3) and Copper oxide (CuO) are employed in the investigation and magnitude are compared with base fluid to ascertain the augmentation of thermal efficiency. Ansys-Fluent 13 used for simulation to identify the augmentation of heat transfer among fluids. A simulation conducted in Laminar flow with Reynolds number (Re) ranges from 20 to 40 at constant heat flux 2000 W/m2. The research reported the contour of temperature distribution, pressure variation, and magnitude velocity, Result reveals that copper oxide nanofluids have produced significant thermal performances than other nanofluid particles.
Athens Journal of Τechnology & Engineering
Flow and heat transfer characteristics in curved ducts are different from that of straight ducts. A numerical study of a steady and three dimensional laminar flow in a 180o curved square duct with longitudinal isosceles triangular rib has been conducted to investigate the effects of rib height, Dean number and volume fraction of Al2O3/water nanofluid on flow and heat transfer characteristics. ANSYS Fluent 17.0 commercial program is used for numerical simulation. Study is implemented for six Dean numbers changing from 250 to 1500, three different rib heights, and eight volume fractions varying from 0% to 5%. Velocity and temperature regions, heat transfer coefficient (h), pressure loss (investigated. Present results are compared with the literature results. It is seen that present results are in good agreement with the results of literature. Results show that Dean number (De), rib height (H) and volume fraction of nanofluid (vof) affect the heat transfer coefficient and pressure drop. It is seen that heat transfer coefficient may be increased by 59.0% for water as the working fluid when longitudinal isosceles triangular rib is used in curved square duct compared to ribless duct. Heat transfer coefficient may also be augmented by 30.8% using nanofluid as the working fluid in a curved square duct with rib. Results show that using longitudinal isosceles triangular rib in a curved square duct is advantageous.