According to increasing human energy requirements and energy source limitation, production of fossil energy is an important issue. Enhanced oil recovery techniques have been developed for increasing the amount of crude oil that can be extracted from oil fields. Recently, the application of nanoparticles (NPs) suspension fl ooding for EOR purposes has been proved. In addition, NPs can improve fl uid-rock interaction characteristics such as wettability. In this work, alpha-Alumina nanofluid effects have been investigated in wettability alteration of carbonated rocks. Contact angle is used to analyze the alteration of surface wettability. Different nanofluids concentration in the range from 0. 1 to 0. 5 wt. % is used. Finally, the result clearly indicates the improvement wettability of reservoir to highly water-wet when it is treated with nanofluids.

The aim of this study was to investigate the surface free energy on the surface of calcite rock and also on the surface of aged calcite in Surfapore Nanofluid using a contact angle measurement. For this purpose, calcite surfaces were prepared by cutting to an approximate size of 3×3×0. 4cm3 and grinded and polished to achieve different roughnesses. The purity and roughness of the samples were determined by X-ray diffraction and atomic force microscopy, respectively. Using the static contact angle on the surface of calcite and calcite aged in the Nanofluid, surface energy determined by three methods of geometric mean, arithmetic mean and Zisman plot showed surface free energy between 30-40mN/m, and polar forces overcome dispersion at calcite surface. After aging calcite surface in the Nanofluid, surface energy reached less than 12mN/m. This surface free energy reduction indicates an increase in the contact angle of the fluids on the aged calcite surface in the Nanofluid. The results of this study will help to better understand the surface properties of calcite in the presence of Nanofluid, as well as how to change its wettability to gas wet conditions, taking into account the static contact angle.

In this study, the onset of nanofluid convection confined within a Hele-Shaw cell is investigated by performing a classical linear stability analysis. The model used for nanofluid combines the effects of Brownian motion and thermophoresis, while for Hele-Shaw cell Brinkman model are employed. The new stability equations are formulated by introducing new characteristic dimensionless parameters such as the Hele-Shaw number, the Hele-Shaw Rayleigh number and the nanoparticle concentration Hele-Shaw Rayleigh number. The resulting stability equations are solved numerically by using higher order Galerkin method. It is found that the nanoparticle concentration Hele-Shaw Rayleigh number, the Lewis number and the modified diffusivity ratio hasten the onset of convection, while the Hele-Shaw number delays the onset of convection.A comparison is also made between the existing boundary conditions for nanoparticle and obtained that the zero nanoparticle flux boundary conditions under the thermophoretic effects has more destabilizing effect than the fixed nanoparticle boundary conditions.

In this paper, a numerical investigation is carried out on mixed convection in a vertical vented rectangular enclosure filled with Al2O3-water nanofluid. The mixed convection effect is attained by heating the right wall by a constant hot temperature and cooling the cavity by an injected or sucked imposed flow. The effects of some pertinent parameters such as the Reynolds number, 100£ Re £ 5000, the solid volume fraction of the nanoparticles, 0£ f £ 0.1, and the aspect ratio of the cavity, 1 £ A £ 4, on flow and temperature patterns as well as on the heat transfer rate within the enclosure are presented for the two ventilation modes. For a value of the aspect ratio A=2, the obtained results demonstrate that the increase of volume fraction of nanoparticles contributes to an enhancement of the heat transfer and to an increase of the mean temperature within the cavity. Also, it was revealed that the fluid suction mode yields the best heat transfer performance.In the case when A is varied from 1 to 4, it was obtained that the heat transfer enhancement, using nanofluids, is more pronounced at shallow enclosures than at tall ones.

The MHD homogeneous-heterogeneous reaction in a nanofluid flow due to a permeable shrinking surface is studied. The bvp4c program in MATLAB is used to obtain the numerical solutions for several values of parameters such as suction parameter, magnetic parameter, nanoparticle volume fraction, heterogeneous reaction and homogeneous reaction rates. The results show that dual solutions exist and the magnetic parameter and the nanoparticle volume fraction widen the range of the solution domain. Suction parameter, magnetic parameter and nanoparticle volume fraction cause the skin friction coefficient to increase and the velocity to decrease. The concentration increases as the nanoparticle volume fraction increases but decrease as the homogeneous reaction rate and heterogeneous reaction rate increase.

In present study, the flow and heat transfer of Water-Cu nanofluid in micro-tube with slip regime with constant wall heat flux numerically simulated with low Reynolds numbers. Slip velocity and temperature jump boundary conditions are also considered along the microtube walls, for first time. The results are presented as the profiles of temperature and velocity. Nusselt number and pressure drop coefficient calculated in interance and full developed region. The effect of slip and using nano particle considerd.It is observed that Nusselt number increases with slip velocity coefficient and pressure drop coefficient decreases; at intrance region the Raynolds of flow has effect on Nusselt and pressure drop coefficient, too.Likewise observed nano particle adding to water has low effect to increases Nusselt number and pressure drop coefficient.

In this study, a linear parabolic trough concentrating photovoltaic/thermal system has been simulated and the effects of using Al2O3/ethylene glycol-water 50: 50 nanofluid with different nanoparticle shapes including platelet, cylindrical, blade and brick shapes from energy and exergy standpoints in the laminar and turbulent regimes have been numerically investigated. The proposed model has been validated using existing experimental results where good agreement was observed. The results indicated that using nanoparticles of cylindrical shape in laminar regime and brick-shaped one in turbulent regime lead to the best system performance compared to others. In addition, applying nanofluid in laminar regime is more effective compared to turbulent regime.

The CFD simulation of heat transfer characteristics of a nanofluid in a circular pipe under convective heat transfer was considered using the fluent software (version 6.3.26) in the laminar flow. Al2O3 nano-particles in water with concentrations of 0.5, 1.0, 1.5, 2 and 2.5% were studied in the simulation. All thermo-physical properties of nanofluids were temperature independent. It was concluded that heat transfer coefficient increased with the Peclet number. Furthermore, the effect of nano-particles concentration on the convective heat transfer coefficient was theoretically investigated and the results were compared with the experimental data obtained from the literature. The maximum convective heat transfer coefficient was observed at the highest concentration of nano-particles in water (2.5%). The simulated data were in good agreement with the literature (with the discrepancy of less than 10%).

In this study, two-dimensional pulsating unsteady flow of nanofluid through a rectangular channel with isothermal walls is investigated numerically. The set of resultant algebraic equations is solved simultaneously using SIMPLE algorithm to obtain the velocity and pressure distribution within the channel. The effects of several parameters, such as volume fraction of different nanoparticles, Reynolds number, and the amplitude and frequency of pulsation flow, on the rate of heat transfer and pressure drop are examined. The results show that the heat transfer enhancement on the target surface obtained by the flow pulsation highly depends on pulsating velocity. It can also be seen that total Nusselt number increases significantly due to increase in amplitude of pulsation and volume fraction of nanoparticles. Analysis also reveals that pressure drop for the alumina nanoparticles is much greater than that of the base fluid.

In this study, energy and exergy efficiency of residential-type direct absorption solar collector using PVP-coated silver nanofluid has been evaluated experimentally. First, stability and thermophysical and optical properties of nanofluid have been considered using the theoretical and experimental methods. Then, outdoor thermal performance of collector is investigated using the experimental setup based on EN12975-2. Results of energy analysis show that the collector efficiency is increased by increase of flowrate and concentration of nanofluid asymptotically. It is observed that exergy efficiency is firstly increased by nanofluid concentration and then, decreased after reaching the optimum value. The optimum concentration was 500 ppm for all flowrates. The variation of exergy efficiency by reduced temperature difference is similar to volume fraction. The optimum exergy efficiency is obtained at 0. 01 m2K/W. The decrease of exergy efficiency by flowrate indicated that exergy losses due to pressure drop have the significant effect on the collector performance.