In this paper, we analyze the effect of heat transfer on the flow of tangent hyperbolic nanofluid in a ciliated tube (fallopian tube where embryo in blood make the development). This study will be beneficial for the researchers and medical experts in the field of embryology. The nanoparticles are beneficial to remove the cysts from the fallopian tube where development of embryo takes place. To resolves the ciliary flow problems, medical doctors use nanoparticles (drug delivery) that may create a temperature gradient. The heat transfer helps to optimize the energy for which the entropy generation is reduced. Therefore, in this research we discuss the heat transfer effect on tangent hyperbolic nanofluid and entropy generation due to ciliary movement. The governing partial differential equations are solved by HPM and software MATHEMATICA?. Effect of viscoelastic parameter, nanoparticles, cilia length and Brinkman number on the velocity, temperature and entropy generation has been illustrated with the help of graphs. Graphical results show that thermal conductivity of fluid increases by adding nanoparticles. The entropy generation due to nanoparticles will decrease the viscosity near the tube wall and blood through tube will flow with normal pressure.
相似文献In the present study, the exact solution of a nanofluid flow and mixed convection within a vertical cylindrical annulus with suction/injection, which is adjacent to the radial magnetic field, is presented with regard to the motion of cylinders’ walls. The impact of Brownian motion and shape factor on the thermal state of CuO–water nanofluid is also considered. The influence of such parameters as Hartmann number, mixed convection parameter, suction/injection, volume fraction of nanoparticles and motion of cylinders’ walls on flow and heat transfer is probed. The results show that the shape of the nanoparticles could change the thermal behavior of the nanofluid and when the nanoparticles are used in the shape of a platelet, the highest Nusselt number is obtained (about 2.5% increasement of Nusselt number on internal cylinders’ wall comparison to spherical shape). The results shed light on the fact that if, for example, the external cylinder is stationary and the internal cylinder moves in the direction of z axis, the maximum and minimum heat transfer take place on the walls of internal and external cylinders, respectively (for η?=?300, about 15% increasement of Nusselt number on internal cylinders’ wall). Furthermore, the enhancement of radius ratio between two cylinders increases the rate of heat transfer and decreases the shear stress on the internal cylinder’s wall.
相似文献The object of this study is to analyze the impact of heterogeneous and homogeneous reactions on the flow, heat and mass transfer analysis of Maxwell nanofluid of Tiwari–Das kind over a stretched cylinder by considering convective boundary condition and velocity slip. Ethylene glycol (Eg) is used as base fluid; while gold (Au) and silver (Ag) are taken as nanoparticles. The governing equations represent nanofluid momentum, and energy and mass are reduced to system of nonlinear ordinary differential equations by utilizing similarity transformation procedure and are numerically evaluated by using finite element method. The sway of several pertinent parameters on the sketches of velocity, temperature and concentration is plotted through graphs. In addition to that the values of rate of heat transfer and skin-friction coefficient are calculated and presented through tables. The values of skin-friction coefficient are intensified as the values of homogeneous–heterogeneous reaction parameters rises. The velocity and concentration scatterings are both declines as the strength of Maxwell parameter raises.
相似文献Turbulent flow characteristics and heat transfer applications of a twisted heat exchanger with 3-lobed cross section along with Y-tape insert are numerically studied. The working fluids for the simulations are pure water and water–Al2O3 nanofluid using two-phase mixture model. The study is carried out for various nanofluid volume fractions of 0.01, 0.02 and 0.03 with Reynolds number in the range of 5000–20,000. The effect of nanoparticles in heat transfer augmentation for smooth and lobed tubes is discussed based on presenting the highest thermal performance, which is a relation between heat transfer rate and pressure loss. Results show that implementing the twisted tube with Y-tape insert enhances the heat transfer more than the twisted tube. Relative Nusselt numbers for twisted tubes decrease with Reynolds number in comparison with the plain tube. Turbulent intensity, swirl number and tangential velocity of twisted tube with insert are higher than empty twisted tube indicating that inserting the Y-tape intensifies the turbulence and disturbs the fluid flow further. On the other hand, although the twisted tube increases the pressure drop more than plain tube, the case with Y-tape drastically increases the friction factor. So, the thermal performance of twisted tube with insert is lower than empty twisted tube. Adding nanoparticles to the base fluid has different influence on the investigated cases. It augments the relative Nusselt number inside plain tube and empty twisted tube with slight increment in friction factor. Increasing the nanoparticles concentration enhances the heat transfer rates for these cases while it does not increase the relative Nusselt number inside twisted tube with Y-tape insert at high Reynolds number and nanoparticle concentration. Moreover, it can be found that twisted tube with or without Y-tape insert is more efficient at low Reynolds number in comparison with the plain tube.
相似文献Pulsating heat pipe (PHP) is a type of wickless heat pipe that has a simple structure and an outstanding thermal performance. Nanofluid is a type of fluid in which nanoparticles are dispersed in a base fluid and have generally a better thermal conductivity in comparison with its base fluid. In this article, the performance of a nanofluid PHP is investigated. Graphene/water nanofluid with a concentration of 1 mg mL?1 and TiO2 (titania)/water nanofluid with a concentration of 10 mg mL?1 are used as the working fluids. To simultaneously investigate the thermal performance and flow regimes in the PHP, a one-turn copper PHP with a Pyrex glass attached to its adiabatic section is used. A one-turn Pyrex PHP is also used to fully visualize flow patterns in the PHP. Our results show that the material for the fabrication of a PHP and temperature of the working fluid are the most important parameters that affect the stability of a nanofluid in the PHP. The more stable nanofluid keeps its stability in the cupper PHP, while the less stable nanofluid starts to aggregate right after the injection to the cupper PHP. The more stable nanofluid has a better thermal performance than water, while the less stable nanofluid has a worse thermal performance than water. In the case of flow regimes, no significant differences are observed between the nanofluid PHP and the water PHP which is different from the previous observations. These results can help researchers to choose the best working fluid for PHPs.
相似文献Investigation of fluid behavior in a cavity enclosure has been a significant issue from the past in the field of fluid mechanics. In the present study, hydrothermal evaluation of hybrid nanofluid with a water–ethylene glycol (50–50%) as the base fluid which contains MoS2–TiO2 hybrid nanoparticles, in an octagon with an elliptical cavity in the middle of it, has been performed. In this problem, the effects of the radiation parameter, porosity, and the magnetic parameter have been analyzed on temperature distribution and fluid flow streamlines and also, on the local and average Nusselt numbers. The governing equations have been solved by the finite element method (FEM). As a novelty, the Taguchi method has been utilized for test design. Further, the response surface method (RSM) has been applied to achieving the optimum value of the involved parameters. The obtained results illustrate that with an augment in the Rayleigh number from 10 to 100, the average Nusselt number will improve by about 61.82%. Additionally, regarding the correlation, it is indeed transparent that the Rayleigh number has the most colossal contribution comparing other factors on the achieved equation, by about 61.88%.
相似文献In this numerical study, laminar flow of water nanofluid/GNP–SDBS (graphene nanoplatelet–sodium dodecylbenzene sulfonate) for 0–0.1% solid nanoparticles mass fraction was investigated for Reynolds numbers of 50–1000 in 3D space via finite volume method. In the newly proposed microchannel design, the cooling fluid is moving in countercurrent in the upper and lower layers of the microchannels, and there are cavities and sinusoidal routes on the solid walls of the microchannel, and the presence of rectangular ribs on the flow centerline along the fluid path enhances mixing for cooling fluid and creates better heat transfer for warm surfaces. The results of this study show that this special design of the microchannel can have a substantial increase in Nusselt number and heat transfer so that in the considered geometry by adding solid nanoparticles mass fraction it is possible to increase average Nusselt number for each Reynolds number by approximately 20%. Also, the mixing of the fluid because of formation of secondary flows has a strong effect on making the temperature distribution uniform in the cooling fluid and solid bed (wall) of the microchannel, especially in the lower layer. The upper layer of the microchannel always has a lower temperature due to indirect contact with heat flux compared with the lower layer. In this study, by increasing Reynolds number and mass fraction of solid nanoparticles the Nusselt number is increased and heat resistance of the lower wall of the microchannel is reduced. Based on the investigation of flow field and heat transfer, the use of the proposed design of the microchannel is recommended for Reynolds number less than 300.
相似文献The thermal performance of a flat-plate solar collector (FPSC) is investigated experimentally and analytically. The studied nanofluid is SiO2/deionized water with volumetric concentration up to 0.6% and nanoparticles diameter of 20–30 nm. The tests and also the modeling are performed based on ASHRAE standard and compared with each other to validate the developed model. The dynamic model is based on the energy balance in a control volume. The system of derived equations is solved by employing an implicit finite difference scheme. Moreover, the thermal conductivity and viscosity of SiO2 nanofluid have been investigated thoroughly. The measurement findings indicate that silica nanoparticles, despite their low thermal conductivity, have a great potential for improving the thermal performance of FPSC. Analyzing the characteristic parameters of solar collector efficiency reveals that the effect of nanoparticles on the performance improvement is more pronounced at higher values of reduced temperature. The thermal efficiency, working fluid outlet temperature and also absorber plate temperature of the modeling have been confirmed with experimental verification. A satisfactory agreement has been achieved between the results. The maximum percentage of deviation for working fluid outlet temperature and collector absorber plate temperature is 0.7% and 3.7%, respectively.
相似文献Numerical studies of laminar forced convective heat transfer and fluid flow in a 2D louvered microchannel with Al2O3/water nanofluids are performed by the lattice Boltzmann method (LBM). Eight louvers are arranged in tandem within the single-pass microchannel. The Reynolds number based on channel hydraulic diameter and bulk mean velocity ranges from 100 to 400, where the Al2O3 fraction varies from 0 to 4%. A double distribution function approach is adopted for modeling fluid flow and heat transfer. Code validations are performed by comparing the streamwise Nusselt number (Nu) profiles and Fanning friction factors of the present LBM and those of the analytical solutions. Good agreements are obtained. Simulated results show that the louver microstructure can disturb the core flow and guide coolant toward the heated walls, thus enhancing the heat transfer significantly. Furthermore, the addition of nanoparticles in microchannels can also augment the heat transfer, but it creates an unnoticeable pressure loss. With both the louver microstructure and nanofluid, a maximum overall Nu enhancement of 7.06 is found relative to that of the fully developed smooth channel.
相似文献This study aimed to investigate the increase in heat transfer in the indirect heater at a city gate station (CGS) with the addition of copper oxide (CuO) nanoparticles to water–ethylene glycol base fluids. Indirect heaters are typically used at CGSs to raise the heat transfer coefficient of output gas flow from ? 5 to 15 °C. Moreover, manufacturing laboratory equipment in the presence of water–ethylene glycol base fluid and the nanoparticle in volume fractions of 0.05, 0.1, 0.2, and 0.3 at a temperature of 40–70 °C was discussed using dimensional simulation and analysis. The physical properties of the base fluid and nanofluid were measured using precise devices. Heat transfer tests for the base and nanofluid, as well as replacing of the air by gas, were conducted in a simulated and developed device. According to the obtained results with respect to the changes in convection and conduction heat transfer, enhancement of temperature difference at a rate of 36% was observed in the indirect heater with nanoparticle volume concentration of 0.2% at a temperature of 70 °C. Moreover, the Nusselt number showed a relatively good agreement with theoretical discussions.
相似文献The heat transfer performance and entropy analysis are done in a compact loop heat pipe (CLHP) with Al2O3/water and Ag/water nanofluid. A compact loop heat pipe having a flat square evaporator with dimensions of 34 mm (L)?×?34 mm (W)?×?19 mm (H) has been fabricated and tested for the heat load ranging from 30 to 500 W. The experimental tests are conducted by keeping the CLHP in the vertical orientation with distilled water, silver (Ag)/water and aluminium oxide (Al2O3)/water nanofluid having low volume concentrations of (0.09% and 0.12%). The effect of wall and vapour temperature, evaporator and condenser heat transfer coefficient, thermal resistance on the applied heat loads is experimentally investigated and compared. The experimental results showed that the evaporator thermal resistance is reduced by 34.70% and 20.21%, respectively, for 0.12 vol% of Ag, Al2O3 nanoparticles when compared with that of the distilled water. For the same volume concentrations of Ag, Al2O3 nanoparticles, an enhancement of 34.52%, 23.7%, 39.27% and 30.8%, respectively, observed for the convective heat transfer coefficients at the evaporator and condenser. The entropy is also reduced by 19.08% and 11.58% when Ag and Al2O3 nanofluids are used as the operating fluid. From the experimental tests, it is found that the addition of small amount of Ag nanoparticles in the working fluid enhanced the operating range by 15% when compared with that of Al2O3/water nanofluid without the occurrence of any dry-out conditions.
相似文献This paper considers the problem of the two-dimensional mixed convection stagnation-point flow of a magnetohydrodynamic non-Newtonian nanofluid bounded by a vertical stretching sheet. Convective surface boundary and zero surface nanoparticle mass flux conditions are employed. The effects of buoyancy, radiation, Brownian motion, thermophoresis, and viscous dissipation are taken into account. The stretching velocity is assumed to vary linearly with the distance from the stagnation point. The fluid is electrically conducted with uniform magnetic field, and the work done due to deformation is taken into consideration. The three-coupled partial differential boundary layer equations are reduced to ordinary differential equations by using proper similarity transformations. Analytical solution by homotopy analysis method is obtained. Effects of different physical parameters on the dynamics of the problem are analyzed and discussed.
相似文献The present work deals with numerical investigations on heat transfer characteristics and friction factor of aqueous CuO nanofluids flow in a set of four microchannels connected in parallel under laminar regime. For each single phase, volume of fluid, mixture and Eulerian models, a particular computer code is developed to carefully simulate this problem. The three-dimensional steady-state governing equations are solved through finite volume method. The primary aim of this study is to comparatively distinguish the most appropriate and accurate model for numerical studies of nanofluids in microchannels. The results are compared with one another and the data obtained from an experimental work. Regarding the results, an acceptable consistency is observed for all models with the experimental data. The current study truly demonstrates that applying single-phase model to simulate and evaluate the laminar flow of CuO–water nanofluid inside microchannels with uniform wall temperature is more modest, precise and reliable compared with two-phase models.
相似文献The main purpose of this study is numerically investigating the flow and heat transfer of nanofluid flow inside a microchannel with L-shaped porous ribs as well as studying the effect of porous media properties on the performance evaluation criterion (PEC) of the fluid. In the present paper, in addition to the pure water fluid, the effect of using water/CuO nanofluid on the PEC of microchannel was investigated. The flow was simulated in four Reynolds numbers and two different volume fractions of nanoparticles in laminar flow regime. The investigated parameters are the thermal conductivity and the porosity rate of porous medium. The results indicate that with the existence of porous ribs, the nanofluid does not have a significant effect on heat transfer increase. By using porous ribs in flow with Reynolds number of 1200, the heat transfer rate increases up to 42% and in flow with Reynolds number of 100, this rate increases by 25%.
相似文献Entropy generation analysis for the Cu–water nanofluid flow through a heat exchanger tube equipped with perforated conical rings is numerically investigated. Frictional and thermal entropy generation rates are defined as functions of velocity and temperature gradients. Governing equations are solved by using finite volume method, and Reynolds number is in the range of 5000–15,000. The effects of geometrical and physical parameters such as Reynolds number, number of holes and nanoparticles volume fraction on the thermal and viscous entropy generation rates and Bejan number are investigated. The results indicate that the thermal irreversibility is dominant in most part of the tube. But it decreases with increasing the nanoparticle volume fraction. Frictional entropy generation reduces with increasing the number of holes from 4 to 10. This is because of stronger velocity gradient near the perforated holes. Bejan number decreases with augment of Reynolds number.
相似文献High-performance cooling is of vital importance for the cutting-edge technology of today, from nanoelectronic mechanical systems to nuclear reactors. Advances in nanotechnology have allowed the development of a new category of coolants, termed nanofluids that have the potential to enhance the thermal performance of conventional heat transfer fluids. At the present time, nanofluids are a controversial research theme, since there is yet no conclusive answer to explain the underlying physical mechanisms of heat transfer. The current study investigates experimentally the heat and mass transfer behaviour of dilute Al2O3–H2O nanofluids under turbulent natural convection—Rayleigh number of the order of 109—in a cubic Rayleigh–Bénard cell with optical access. Traditional heat transfer measurements were combined with a velocimetry method to obtain a deeper understanding of the impact of nanoparticles on the heat transfer performance of the base fluid. Particle image velocimetry was employed to quantify the resulting mean velocity field and flow structures in dilute nanofluids under natural convection, at three parallel planes inside the cubic cell. All the results were compared with that for the base fluid, i.e. deionised water. It was observed that the presence of a minute amount of Al2O3 nanoparticles in deionised water, φv =?0.00026 vol.%, considerably modifies the mass transfer behaviour of the fluid in the bulk region of turbulent Rayleigh–Bénard convection. Simultaneously, the general heat transport, as expressed by the Nusselt number, remained unaffected within the experimental uncertainty.
相似文献In this study, the rheological behavior and viscosity of a stable nanofluid, which is prepared with the suspension of MCM-41 nanoparticles in SAE40 engine oil as base fluid, would be presented. Two-step method has been used to stabilize the nanoparticles in engine oil. To obtain structural and morphological properties of the synthesized nanoparticles, small-angle X-ray scattering, N2 adsorption/desorption analysis and scanning electron microscopy have been done. Then, viscosity of nanofluids has been measured in temperature range of 25–55 °C, shear rates up to 13,000 s?1 and different concentrations (0 mass%, 0.5 mass%, 1 mass%, 3 mass% and 5 mass% of MCM-41 nanoparticles). For all the samples, the shear stress versus shear rate diagrams showed that SAE40 oil has Newtonian behavior, in which adding mesoporous silica nanoparticles causes non-Newtonian or pseudoplastic behavior. The results declared that viscosity decreases with increasing temperature and increases with an enhancement in concentration. Furthermore, based on experimental results, an accurate correlation has been proposed to predict the viscosity of SAE40/MCM-41 nanolubricants.
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