Experimental investigation of thermal efficiency in shell and helically coiled tube heat exchangers with 𝐅 𝐞 𝟑 𝐎 𝟒 magnetite nanoparticles

Nanotechnology research has proved sustainable results for a wide range of applications from engineering to medical science. Nanotechnology corresponds to the engineering of materials in nanosize (10-9m) whose material properties differ from of bulk properties. Nanofluid is one category of applications reported for its use as thermal management in cooling of electronic devices and fuel cell applications. In most literature, electrical conductivity studies were used as a basis to define the stability of nano-suspensions. In the present paper, the electrical conductivity studies of two glycol based nanofluids dispersed with ZnO nanoparticles of 50nm average diameter in the temperature range of 30-550C are reported. ZnO nanoparticles are added to the aqueous glycol base fluid prepared with (30 EG: 70 Water) and (30 PG: 70 Water) composition at a low volume concentration of 0. 01 to 0. 05%. Correlations are developed using experimental results for each volume concentration to predict electrical conductivity (EC) of nanofluids with temperature. From obtained results, the electrical conductivity of aqueous propylene glycol shows a decrement in EC after adding ZnO nanoparticles (except at 0. 04% volume concentration) and vice versa for aqueous ethylene glycol. For aqueous propylene and ethylene glycol nanofluids, electrical conductivity enhancement up to 20% and 12% is obtained at a volume concentration of 0. 04% and 0. 01% at 550C temperature respectively. The electrical conductivity of both nanofluids increases with increase in temperature at all volume concentrations.

In this research, two carbon structures silica nanohybrids Pickering emulsions were prepared. Graphite and activated carbon were carbon allotropes with different morphologies of laminar and spherical, respectively. The effect of carbon morphology investigated on the related silica nanohybrids Pickering emulsions for C-EOR. Therefore, nanohybrids were prepared with graphite and activated carbon through the sol-gel method based on different weight percents and two different methods. X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), and Thermal Gravimetric Analysis (TGA) used characterize the synthesized samples. Pickering emulsions of these nanohybrids were prepared by utilizing octane as oil model, suitable anionic surfactants and an alcoholic co-surfactant with pH=7 at room temperature using distilled water. The apparent stability of Pickering emulsion studied over a period of one month. The results of analyses indicated that graphite/silica nanohybrids Pickering emulsions had superior properties for C-EOR in comparison to activated carbon/silica nanohybrids Pickering emulsions. It concluded that laminar morphology is more significant than the spherical morphology of carbon structure for the mentioned purpose. According to emulsion phase morphology, the optical microscopic images showed that the best samples were 70% graphite/silica (method 2) and 50% activated carbon/silica (method 2). The results of contact angle measurement represented that the 70% graphite/silica nanohybrid (method 2) is more effective on the stone reservoir improvement, which can change the wettability from oil-wet to water-wet. Nanofluid of 70% graphite/silica nanohybrid (method 2) could reduce interfacial tension.

This paper focuses on developing a new method that represents user-accessible correlation for the estimation of water-based nanofluids viscosity. For this, an evolutionary algorithm, namely Gene Expression Programming (GEP), was adapted based on a wide selection of literature published databanks including 819 water-based nanofluids viscosity points. The developed model utilized the base fluid viscosity as well as volume fraction and size of the nanoparticles as the inputs of the model. Several statistical parameters integrated with graphical plots were employed in order to assess the accuracy of the proposed GEP-based model. Results of the evaluation demonstrate fairly enough accuracy of the developed model with statistical parameters of AARD%=11. 7913, RMSE=0. 3567, and SD=0. 1851. Furthermore, the trend analysis indicates that the GEP calculated points satisfactorily follow the trend of the nanofluid viscosity variation as a function of different model inputs. To provide more verification, the proposed GEP model was compared with some literature theoretical and empirical correlations leading to the supremacy of the developed model here. The applied sensitivity analysis reveals that the highest impact value is assigned to the volume fraction of the nanoparticle. Moreover, the outlier’ s detection by Williams’ technique illustrates that about 96. 5% of the GEP estimates are in the applicability domain resulting in the validity of the proposed model in this study. At last, the results of this study demonstrate that the new method here outperform other literature-published correlations from the standpoint of accuracy and reliability.

Introduction: The aim of this research was to study the impact of various doxorubicin (Dox)-containing nanofluids, e. g. singlewalled carbon nanotube (SWCNT)+Dox, graphene oxide (GO)+Dox and Dextran-PNIPAM (copolymer)+Dox mixtures on HeLa cells (human transformed cervix epithelial cells, as a model for cancer cells) depending on their concentration. Methods: Structural analysis of GO+Dox complex was accomplished using Hartree-Fock level of theory in 6-31G** basis set in Gaussian. Dynamic light scattering (DLS), zeta-potential, scanning electron microscopy and confocal laser scanning microscopy were used. The cell viability was analyzed by the MTT assay. Results: The viability of HeLa cells was studied with the MTT assay after the incubation with various Dox-containing dispersions depending on their concentration. The size of the particles was determined by DLS. The morphology of the nanoparticles (NPs) was studied by scanning electron microscopy and their uptake into cells was visualized by confocal laser scanning microscopy. It was found that the Dextran-PNIPAM+Dox nanofluid in contrast to Dox alone showed higher toxicity towards HeLa cells up to 80% after 24 hours of incubation, whereas the SWCNT+Dox and GO+Dox nanofluids at the same concentrations protected cells from Dox. Conclusion: The importance of Dextran-PNIPAM copolymer as a universal platform for drug delivery was established, and the huge potential of Dextran-PNIPAM+Dox NPs as novel anticancer agents was noted. Based on the in vitro study of the SWCNT+Dox and GO+Dox nanofluids, it was concluded that SWCNT and GO NPs can be effective cytoprotectors against the highly toxic drugs.

In this study, the laminar forced convection heat transfer of water-coper nanofluid is numerically investigated within a parallel plate channel. Fixed temperature heat sources with the specified sizes and distances are embedded on the walls of the channel. The entry and exit sections of the channel as well as the sections between the heat sources are thermally insulated. The fluid flow with uniform velocity and temperature enters the channel. The channel length is considered large enough, so the flow in the channel output is assumed fully developed. The aim of this research is the numerical investigation of the effects of the Reynolds number, the solid volume fraction and the number of the heat sources on the flow field and heat transfer rate. For this purpose, the governing equations are discretized by finite difference method based on the control volume formulation and are solved using the SIMPLE algorithm. In order to validate the computer program, the results of this study have been compared with the results of the previous numerical studies. This comparison has confirmed the accuracy of the performance of the computer program. The results show that the rate of heat transfer increases by increasing the solid volume fraction and Reynolds number. The results also show that, heat transfer rate increases when the heat sourse is divided into smaller sections and these sections are distributed on the channel wall.

In this work, we study numerically the natural convection of NanoFluids (NF) in an inclined flat bottom flask,it is one of the laboratory flasks used in organic chemistry synthesis. The main reason for this study is to enhance the thermal properties of the reaction medium inside the flat bottom flask and to ameliorate the rate of chemical reactions using nanofluids. The flat bottom wall is maintained at a constant high-temperature Th. While the top, left and right walls of the cavity are maintained at a low-temperature TL. The NF comprises Cu and Al2O3 NanoParticles (NP) suspended in pure water. The governing equations are solved numerically using the finite-volume approach and formulated using the Boussinesq approximation. In this simulation we examined the effects of the NP volume fraction (φ, ) from 0% to 5%, the Rayleigh number from 103 to 106, the various inclination angles of enclosure (γ, =0°, , 5°, , 10°, , 15°, ) and the NF type (Cu and Al2O3) on the flow streamlines, isotherm distribution, and Nusselt number. The obtained results show that the addition of Cu and Al2O3 NP increases the mean Nusselt number which enhances the heat transfer in the flat bottom flask and causes significant changes in the flow pattern. In addition, the mean Nusselt number is increased with increasing the Rayleigh number and the volume fraction, and the best results have been obtained from the Cu nanofluid. Also, as the inclination angle increases the mean Nusselt number decreases, and the highest value of the Nusselt number was obtained for a vertical enclosure (γ, =0°, ). The obtained streamlines are mostly symmetric and their values are generally increased by increasing the Rayleigh number and volume fractions of NPs. Besides, the obtained isotherms generally follow the geometry of the flat bottom flask.

The effect of NiO nanoparticles on the rheological and volumetric properties of the dilute solutions of starch-NaOH-H2O, PEG400- PEG2000 and PEG400-PEG6000 was investigated. To this end, the stable nanofluids should have bee prepared, therefor, the nanoparticles of NiO were added to these solutions and dispersed by a shaker and an ultrasonic bath for making the homogeneous nanofluids. The UVVis spectroscopy, zeta potential and dynamic light scattering were used to specify the stability and particle size distribution of colloidal solutions studied. Fluid flow and suspense structure of NiO nanoparticles in the solutions of starch-NaOH-H2O, PEG400-PEG2000 and PEG400-PEG6000 were studied by measuring the magneto rheological properties at T=298.15 K. Pseudoplastic (or shear-thinning) behavior was observed for all the suspensions investigated. Bingham plastic, Herschel-Bulkley and Carreau-Yasuda models were applied for modeling the magnetorheological properties of nanofluids. The density values of NiO-starch-NaOH-H2O, NiO-PEG400-PEG2000 and NiO-PEG400-PEG6000 nanofluids were also measured at T= (298.15, 308.15 and 318.15) K. The excess molar volumes were calculated from the density data for highlighting the interparticle interactions occurred in the nanofluids. Singhet al. equation was used for fitting the excess molar volume values. The trend of excess molar volumes of nanofluids with concentration indicated that the significant interactions observed in NiO-starch-NaOH-H2O nanofluid are attractive interactions and in NiO-PEG400-PEG2000 and NiO-PEG400-PEG6000 colloidal solutions are van der Waals-type interactions.

The current research aims at conducting an experimental and theoretical investigation on the performance of air dehumidification system using a nanofluid of g-alumina nano-particles in LiBr/H2O, as a desiccant. Comparative experiments organized using a central composite design are carried out to evaluate the effects of six numerical indices (air velocity, desiccant flow rate, air humidity ratio, desiccant solution concentration, air temperature, desiccant temperature) and one categorical factor (adding nano-particles), on outlet air humidity ratio and outlet air temperature as responses. Reduced quadratic regression models are derived for each response. The obtained results revealed that LiBr/H2O solution concentration and air temperature have the most significant effect on outlet air humidity ratio and outlet air temperature, respectively. It was found that the average rates of mass transfer and heat transfer increased to 12.23 % and 13.22 %, respectively, when g-alumina nano-particles (0.02 wt %) were added to the LiBr/H2O solution. The average rates of mass and heat transfer coefficients increased to 22.73 % and 26.51 %, respectively.

Magnetic field effect on unsteady natural convection heat transfer of Cu–Water nanofluid in a square porous cavity was studied numerically in here. At first, initial temprature of the cavity was Ti and vertical walls were at temperature Tc = Ti Suddenly the right wall’s tamprature was changed to Th and the horizontal walls were adiabatic. The effective parameters in this study were Ra, Ha, and j. which appear in the non-dimensionalized equations. Ra is a function of temperature difference between hot and cold walls, Ha is a parameter that depends on the magnetic field, and j is the volume fraction of nano particles. The non-dimensionalized governing equations were obtained based on darcy model. A control volume approach was used for solving these equations. The effect of the variation of parameters, Ra , Ha and j, on heat transfer rate, fluid flow, isotherms, and the steady time of solution were investigated. The solutions show that steady time decreases, as Ra increases or j decrease. While, variation of Ha for high Ra has different effects on steady time.