Numerical investigation of Al2O3/water nanofluid laminar convective heat transfer through triangular ducts

In this article, laminar flow-forced convective heat transfer of Al2O3/water nanofluid in a triangular duct under constant wall temperature condition is investigated numerically. In this investigation, the effects of parameters, such as nanoparticles diameter, concentration, and Reynolds number on the enhancement of nanofluids heat transfer is studied. Besides, the comparison between nanofluid and pure fluid heat transfer is achieved in this article. Sometimes, because of pressure drop limitations, the need for non-circular ducts arises in many heat transfer applications. The low heat transfer rate of non-circular ducts is one the limitations of these systems, and utilization of nanofluid instead of pure fluid because of its potential to increase heat transfer of system can compensate this problem. In this article, for considering the presence of nanoparticl: es, the dispersion model is used. Numerical results represent an enhancement of heat transfer of fluid associated with changing to the suspension of nanometer-sized particles in the triangular duct. The results of the present model indicate that the nanofluid Nusselt number increases with increasing concentration of nanoparticles and decreasing diameter. Also, the enhancement of the fluid heat transfer becomes better at high Re in laminar flow with the addition of nanoparticles

Experimental Investigation of nanofluid heat transfer in a square cross-sectional duct

English version Forced convective heat transfer of two different nanofluids including AL$_2$O$_3$-water and CuO-water in laminar flow through square cross section duct under constant heat flux has been investigated. The Nusselt number and average convective heat transfer coefficient for different nanoparticles concentrations as a function of Peclet number have been analyzed. AL$_2$O$_3$-water nanofluid with 0.2, 0.5, 1.0, 1.5, 2.0 and 2.5 percent volume fractions has been tested. The maximum enhancement of convective heat transfer coefficient for each of the above mentioned concentrations was 7, 10, 13, 18, 22, 27 percent, respectively. Also, CuO-water nanofluid was tested at 0.1, 0.2, 0.5, 0.8, 1.0 and 1.5 percent volume fractions and the results show that the maximum enhancement of convective heat transfer coefficient for each concentration was 8, 10, 14, 16, 19, 21 percent, respectively.Comment: 6 pages, in Persia

Omid Mahian Young Researchers Club, Effect of Uncertainties in Physical Properties on Entropy Generation Between Two Rotating Cylinders With Nanofluids

In this paper, the effects of uncertainties in physical properties on predicting entropy generation for a steady laminar flow of Al 2 O 3 -ethylene glycol nanofluid (0 / 6%Þ between two concentric rotating cylinders are investigated. For this purpose, six different models by combining of three relations for thermal conductivity (Bruggeman, Hamilton-Crosser, and Yu-Choi) and two relations for dynamic viscosity (Brinkman and Maiga et al.) are applied. The governing equations with reasonable assumptions in cylindrical coordinates are simplified and solved to obtain analytical expressions for average entropy generation ðN S Þ ave and average Bejan number ðBeÞ ave . The results show that, when the contribution of heat transfer to entropy generation for the base fluid is dominant, a critical radius ratio ðP C Þ can be determined at which all six models predict the reduction in entropy generation with increases of volume fraction of nanoparticles. It is also found that, when the contribution of viscous effects to entropy generation is adequately high for the base fluid (/ ¼ 0), all models predict the increase of entropy generation with increases of particle loading

Viscosity, tribological and physicochemical features of ZnO and MoS2 diesel oil-based nanofluids: An experimental study

International audienceIn this research, two different diesel oil-based nanofluids were prepared and the influence of temperature and nanoparticle content were examined on viscosity, tribological, and physicochemical features of diesel oil. The kinematic viscosity of samples was experimentally evaluated based on standard ASTM D445. The greatest viscosity increment was diagnosed at 0.7 wt% and 100 °C for both of the prepared nanofluids. The anti-friction behavior of the nanofluids was studied utilizing a pin-on-disc tribometer. The acquired outcomes revealed that ZnO and MoS2 nanoparticles (NPs) could promote the tribological characteristics of pure diesel oil. By analyzing the friction coefficient values and line roughness of the wear surface (Ra), an optimal concentration of ZnO and MoS2 nanoparticles (NPs) were found to be around 0.4 wt% and 0.7 wt%, respectively. The friction factor and pumping power were also measured at diverse content of nanoparticles and flow rates showing that the pumping power was enhanced by the incorporation of nanoparticles

Experimental comparison between ZnO and MoS2 nanoparticles as additives on performance of diesel oil-based nano lubricant

International audienceThis study compares the tribological and thermophysical features of the lubricating oil using MoS2 and ZnO nano-additives. The average size of MoS2 and ZnO nanoparticles were 90 nm and 30 nm, respectively. The nanoparticles were suspended using Triton X-100 in three different concentrations (0.1, 0.4 and 0.7 wt.%) in a commercial diesel oil. Tribological properties such as mass loss of the pins, friction coefficient, and worn surface morphologies and thermophysical properties such as viscosity, viscosity index, flash point and pour point of resulting nano lubricant were evaluated and compared with those of pure diesel oil. The tribological behavior of nano lubricants was evaluated using a pin-on-disc tribometer. The worn surface morphologies were observed by scanning electron microscopy. The overall results of this experiment reveal that the addition of nano-MoS2 reduces the mass loss values of the pins in 93% due to the nano-MoS2 lubricant effect. With 0.7 wt.% in nanoparticles content, the viscosity of MoS2 and ZnO nano lubricants at 100 °C increased by about 9.58% and 10.14%, respectively. Pure oil containing 0.7 wt.% of each nanoparticle increased the flash point because of its small size and surface modifying behavior compared to the pure oil. Moreover, the addition of ZnO nanoparticles with pure oil lubricant is more suitable than MoS2 nanoparticles for improving the thermophysical properties of pure oil

Experimental investigation on thermal performance of covalently functionalized hydroxylated and non-covalently functionalized multi-walled carbon nanotubes/transformer oil nanofluid

International audienceThe study investigated the effect of adding covalently functionalized-hydroxylated multi-walled carbon nanotubes (MWCNTs-OH) and non-covalently-functionalized MWCNTs on the breakdown voltage and thermal properties of transformer oil in a rectangular chamber. The novelty of the present study is the use of covalently functionalized hydroxylated and non-covalently functionalized multi-walled carbon nanotubes in transformer oil, and the reason for the selection of these nanoparticles is the high intrinsic thermal conductivity compared to other nanoparticles. Between both studied nanofluids, the thermal and electrical performance of covalently functionalized MWCNTs-OH was better due to the highest increase in heat transfer coefficient of free transfer and using fan was related to covalently functionalized MWCNTs-OH, which increased by 26.23% and 30.08%, respectively. Also, by measuring the breakdown voltage, it was found that the MWCNTs-OH of 0.001 wt% had the lowest reduction compared to the base fluid and was equal to 55.6 kV, which showed good performance because the specified standard for transformer oil breakdown voltage property is between 30 kV and 70 kV. According to the results, covalently functionalized hydroxylated MWCNTs-OH/transformer oil nanofluid has better thermal performance than pure oil, which prevents the transformer from rising in temperature and can also be used as electrical insulation in transformers

On-line bed thickness measurement of self clearing continuous centrifuge using laser application

The Self Clearing Continuous Centrifuges (SCCC) are mainly used in sugar factories for the separation of sugar crystals from molasses. Variation of bed thickness in a SCCC is expected to play an important role in the quality of sugar crystals. However since baskets are normally rotating at a speed of more than 1000 rpm, measuring the bed thickness is a difficult task which is tackled as a part of this research. This paper describes and discusses the design and development of an optical method based on laser technology application to measure the bed thickness on-line on a (SCCC) which does not interfere with flow behavior in the basket

Experimental investigation of indirect heat transfer through a novel designed lab-scale setup using functionalized MWCNTs nanofluids (MWCNTs-COOH/water and MWCNTs- OH/water)

This study aims to investigate the influence of functionalized multi-walled carbon nanotubes (MWCNTs-COOH and MWCNTs-OH) on the performance of a novel indirect laboratory heater redesigned with a helical tube. Experiments were performed using a bath of water and the two nanofluids mentioned above. The nanofluids were prepared at concentrations of (0.025, 0.05, 0.075, and 0.1) wt%. To ensure the stability of the utilized nanofluids and the structure of the nanoparticles, characterization studies such as dynamic light scattering (DLS), FT-IR, and XRD were carried out. The results indicated that when concentration levels rose, the system's performance rose as well. For instance, the MWCNTs-COOH nanofluid bath had a maximum heat transfer rate of 1709 W, which was 19.04% better than pure water, and a maximum Nusselt number of 15.61, which was an increase of 36.33% over pure water. In summary, heat loss increased with an increment in flow rate, and by increasing the concentration of nanofluids, the lowest heat loss, the highest heat transfer rate, and the best efficiency of the system were achieved. This study can establish the foundation for redesigning indirect heaters to reduce thermal energy consumption and for further research on the use of nanofluids in indirect bath heating

Numerical investigation of Al₂O₃/water nanofluid laminar convective heat transfer through triangular ducts

<p>Abstract</p> <p>In this article, laminar flow-forced convective heat transfer of Al₂O₃/water nanofluid in a triangular duct under constant wall temperature condition is investigated numerically. In this investigation, the effects of parameters, such as nanoparticles diameter, concentration, and Reynolds number on the enhancement of nanofluids heat transfer is studied. Besides, the comparison between nanofluid and pure fluid heat transfer is achieved in this article. Sometimes, because of pressure drop limitations, the need for non-circular ducts arises in many heat transfer applications. The low heat transfer rate of non-circular ducts is one the limitations of these systems, and utilization of nanofluid instead of pure fluid because of its potential to increase heat transfer of system can compensate this problem. In this article, for considering the presence of nanoparticl: es, the dispersion model is used. Numerical results represent an enhancement of heat transfer of fluid associated with changing to the suspension of nanometer-sized particles in the triangular duct. The results of the present model indicate that the nanofluid Nusselt number increases with increasing concentration of nanoparticles and decreasing diameter. Also, the enhancement of the fluid heat transfer becomes better at high Re in laminar flow with the addition of nanoparticles.</p