To date, various designs have been proposed to increase the efficiency of radiative coolers with approaches such as changes in materials and their properties, size and shape of the elements, and ...structures geometry. In the present work, an attempt has been made to obtain this important issue by presenting an innovative strategy from a new perspective. In this strategy, by keeping the face exposed to solar energy away from the body, heat distribution can be inhibited, which leads to a decrease in body temperature. This act simultaneously provides a higher operating temperature for the emitter section, thereby enhancing the exergy of the system. On the other hand, the presence of the thermal diode allows the surface of the object to continue to radiate its heat. Hence, several experiments were designed and performed to evaluate the performance of the strategy by an experimental apparatus built for this purpose. Initially, the rectification ratio results of constructed rectifier mirrors showed that the light transmission amount in the forward path is nearly 44% higher than in the reverse direction. In the next step, the temperature measurement of the samples showed the sub-ambient temperature for the present work with a difference of 9 and 2 °C, against direct sunlight and the night sky, respectively. This model also has a high-temperature difference of about 13, 11, and 6.5 °C during the day and 1.6, 0.5, and 0.5 °C at night below the other three samples. This superiority was maintained in cloudy weather conditions as well as thermal shock stability. One of the most important applications of radiation coolers is in the aerospace industry. In this particular application, in addition to cooling, it is vital to protect the equipment against thermal shock caused by sudden and extreme temperature differences in space. Due to obtaining results such as efficient cooling rate, and high resistance to thermal shock, this concept provides a practical vision for improving the spacecraft's cooling systems.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
A new type of nanofluids is known as hybrid nanofluids, which is prepared by suspending two or different forms of nanoparticles and hybrid nanoparticles in the considered base fluid. Recently, ...researchers have indicated that hybrid nanofluids can effectively substitute the convectional coolant especially those working at very high temperatures. In this investigation, a kind of hybrid nanofluid including copper oxide (CuO 29–50 nm) and silver (Ag 2–5 nm) nanoparticles with water as base fluid is analytically modeled to develop the problem of the nodal/saddle stagnation-point boundary layer flow and heat transfer. A new straightforward mathematical model has been presented and formulated based on Tiwari–Das nanofluid scheme. Using appropriate similarity variables, the non-linear governing PDEs are transformed into non-linear dimensionless ODEs, which are solved analytically by the well-known homotopy analysis method (HAM) and numerically using the bvp4c function from MATLAB software. For the theoretical assessment of the hemodynamics and thermal impacts, graphical configurations are plotted for the different emerging parameters. These patterns provide an interesting understanding of this theoretical model to the industrial applications. Moreover, the good agreement of present achievements with previously reported results demonstrates that the developed model can be used with great confidence to study the flow and heat transfer of hybrid nanofluid in various problems. Besides, the thermal characteristics of hybrid nanofluid are found to be higher in comparison to the base fluid and fluid containing single nanoparticles, respectively.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The purpose of this study is to present simulation and numerical solutions to the unsteady flow and heat transfer near stagnation point over a stretching/shrinking sheet in porous medium filled with ...a hybrid nanofluid. Water (base fluid), nanoparticles of titania and copper were considered as a hybrid nanofluid. It is worth mentioning that evaluating the heat transfer enhancement due to the use of hybrid nanofluids has recently become the center of interest for many researchers. The coupled non-linear boundary-layer equations governing the flow and heat transfer are derived and reduced to a set of coupled non-dimensional equations using the appropriate transformations and then solved numerically as a nonlinear boundary value problem by bvp4c scheme from MATLAB. To validate the modeling of hybrid nanofluid and also numerical procedure, the value of the skin friction and the heat transfer rate for the limited cases of pure water, titania/water and copper/water is obtained and compared with previously reported results that demonstrate an excellent agreement. In the present investigation, the thermal characteristics of hybrid nanofluid are found to be higher in comparison to the base fluid and fluid containing single nanoparticles, respectively. It can be concluded that both skin friction coefficient and local Nusselt number enhance almost linearly with increasing the copper nanoparticle volume fraction (as second nanoparticle). Besides, the porosity and the magnetic effect amplify heat transfer rate, while the unsteadiness parameter has a reducing effect on heat transfer rate in problem conditions.
Sonoporation is a non-invasive method that uses ultrasound for drug and gene delivery for therapeutic purposes. Here, both Finite Element Method (FEM) and Lattice Boltzmann Method (LBM) are applied ...to study the interaction physics of microbubble oscillation and collapse near flexible tissue. After validating the Finite Element Method with the nonlinear excited lipid-coated microbubble as well as the Lattice Boltzmann Method with experimental results, we have studied the behavior of a three-dimensional compressible microbubble in the vicinity of tissue. In the FEM phase, the oscillation microbubble with a lipid shell interacts with the boundary. The range of pressure and ultrasound frequency have been considered in the field of therapeutic applications of sonoporation. The viscoelastic and interfacial tension as the coating properties of the microbubble shell have been investigated. The presence of an elastic boundary increases the resonance frequency of the microbubble compared to that of a free microbubble. The increase in pressure leads to an expansion in the range of the microbubble’s motion, the velocity induced in the fluid, and the shear stress on the boundary walls of tissue. An enhancement in the surface tension of the microbubble can influence fluid flow and reduce the shear stress on the boundary. The multi-pseudo-potential interaction LBM is used to reduce thermodynamic inconsistency and high-density ratio in a two-phase system for modeling the cavitation process. The three-dimensional shape of the microbubble during the collapse stages and the counter of pressure are displayed. There is a time difference between the occurrence of maximum velocity and pressure. All results in detail are presented in the article bodies.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Here, the squeezing unsteady 2-dimensional incompressible hybrid nanofluid flow between two collateral sheets has been investigated numerically, considering the influences of magnetic field and the ...mutable thermal conductivity. The solid-particles are the magnetite (Fe3O4) and the carbon nanotubes (CNTs) inserted in the base liquid (water). To give a complete development investigation of the present problem, the influences of a heat source/sink have also been analyzed. The technique used is pursuant to the Tiwari-Das nanofluid method which nanoparticle weights are considered instead of the volumetric concentration of the solid-particles. At first, the controlling dimensional PDEs, including continuity, momentum conservation, and energy conservation, are changed to a non-dimensional ODEs system applying adequate similarity reduction. The Runge–Kutta–Fehlberg (RK4) approach and shooting procedure is utilized to solve nonlinear ODEs system numerically. The impression of the controlling parameters on the temperature and velocity of working fluid as well as the Nusselt number, and the skin friction has been studied and analyzed. The mass-based manner gives trustable results for the flow and heat transfer analysis in the presence heat generation source and also an oblique magnetic ground. The results demonstrate that the entity of temperature-dependent thermal conductivity and the oblique magnetic ground reduces heat transfer. Furthermore, the greatest temperature distribution was related to spherical solid-particles in the presence of a horizontal magnetic ground.
•The presence of an oblique magnetic field and the temperature-dependent thermal conductivity realize a decrease in heat transfer rate.•The horizontally applied magnetic field has the highest temperature distribution and heat transfer rate.•Existence of heat source and more Eckert number raise the temperature distribution between the sheets.•The highest rate of heat transfer was related to spherical and single type solid-particles.•The effect of Hartmann parameter on the skin friction has been observed to be about 19 times greater than that the effect of squeeze parameter.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Here, a mass-based hybridity model is applied to inquire about the mixed convection of a thermomicropolar binary nanofluid (TMBNF) upon a shrinking and porous plate. The nanoparticles are the silver ...(AgNPs) and the graphene (GrNPs), in a spherical shape, suspended in an aqua base fluid. The applied methodology considers the masses of base fluid and nanoparticles as an alternative to the first and second nanoparticles volume fraction, according to the single-phase approach named the Tiwari-Das model. By using the similarity transformation technique, the dominating PDEs are changed to a system of ODEs that can be solved numerically by the bvp4c pattern of Matlab. To validate the numerical method, a comparison is implemented for the heat transfer, the shear stress, and the gradient of microrotation values, with results reported previously that consequently a supreme agreement is observed. The variations of the angular velocity, velocity, temperature distribution, gradient of microrotation, shear stress, and the heat transfer of the TMBNF with the prominent parameters are presented and analyzed by the tabular and graphical results. The originality of this work is related to the use of the mass-based model for TMBNF flow and the derivation of a new configuration of governing equations. It is concluded that the mass-based model with its significant benefits can be utilized successfully with tremendous assurance to abundant theoretical problems of micropolar binary nanofluid flow and heat transfer. New models for the nanofluid hybridity can undoubtedly be quite helpful in the many fields where cooling technologies are essential.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Heat absorption and thermal radiation have significant roles in engineering and research. These two principles have applications in thermal transportation, gas turbines, nuclear power plants, ...electrical fuel, aerospace engineering, projectiles and renewable energy. The present work analyses the stagnation point ternary nanofluid motion over a circulating sphere in the presence of a magnetic field and radiation absorption. The nonlinear controlling equations are replaced by ordinary differential equations by applying a suitable comparison factor. The bvp4c process was used to establish numerical outcomes of the partial differential equations. This mathematical numerical findings are presented graphically. The results of ternary nanoparticles (Cu–Ag–CuO/water), hybrid nanoparticles (Cu–Ag/water) and copper (Cu) nanoparticles have also been compared, and this comparison suggests that ternary nanoparticles (Cu–Ag–CuO/water) are more effective at attenuating hemodynamic factors (such as wall shear stress and heat transfer) than hybrid and copper (Cu) nanoparticles. Comparison with previous literature results is also done and the results are found to be in very good agreement with those published earlier.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In this article, the unsteady magnetohydrodynamic （MHD） stagnation point flow and heat transfer of a nanofluid over a stretching/shrinking sheet is investigated numerically. The similarity solution ...is used to reduce the governing system of partial differential equations to a set of nonlinear ordinary differential equations which are then solved numerically using the fourth-order Runge-Kutta method with shooting technique. The ambient fluid velocity, stretching/shrinking velocity of sheet, and the wall temperature are assumed to vary linearly with the distance from the stagnation point. To investigate the influence of various pertinent parameters, graphical results for the local Nusselt number, the skin friction coefficient, velocity profile, and temperature profile are presented for different values of the governing parameters for three types of nanoparticles, namely copper, alumina, and titania in the water-based fluid. It is found that the dual solution exists for the decelerating flow. Numerical results show that the extent of the dual solution domain increases with the increases of velocity ratio, magnetic parameter, and permeability parameter whereas it remains constant as the value of solid volume fraction of nanoparticles changes. Also, it is found that permeability parameter has a greater effect on the flow and heat transfer of a nanofluid than the magnetic parameter.
This study intends to semi-analytically investigate the steady 3D boundary layer flow of a SiC-TiO2/DO hybrid nanofluid over a porous spinning disk subject to a constant vertical magnetic field. ...Here, the novel attitude to single-phase hybrid nanofluid model corresponds to considering nanoparticles and base fluid masses to compute solid equivalent volume fraction, solid equivalent density, and also solid equivalent specific heat at constant pressure. The basic PDEs are transformed into dimensionless ODEs using Von Kármán similarity transformations, which are then solved numerically using bvp4c function. Results indicate that mass suction and magnetic field effects diminish all hydrodynamic and thermal boundary layer thicknesses. Finally, a significant report is presented to investigate quantities of engineering interest due to governing parameters’ effects.
In this article, the natural-convective flow of an electrically conducting nanofluid adjacent to a spinning down-pointing vertical cone in the presence of transverse magnetic field is studied. The ...mathematical model has been formulated based on Tiwari-Das nanofluid model. Three different types of water-based nanofluid with copper, aluminum oxide (alumina) and titanium dioxide (titania) as nanoparticles are considered in this investigation. Two cases of heat transfer analysis are discussed. These are: (i) the spinning cone with prescribed surface temperature and (ii) the spinning cone with prescribed surface heat flux. Using appropriate transformations, the system of partial differential equations is transformed into an ordinary differential system of three equations, which is solved numerically using the fourth-order Runge-Kutta method with shooting technique. The current solution demonstrates very good agreement with those of the previously published studies in the especial cases. The effects of the three key thermophysical parameters governing the flow; the nanoparticle volume fraction, the magnetic parameter and the spin parameter on dimensionless velocity and temperature distributions, skin friction coefficient, Nusselt number and entropy generation number are presented graphically and discussed in details. Our results demonstrate that, the enhancement of heat transfer is a function of particle concentration, small fraction of metallic particles leading to significant changes in all three quantities of skin friction coefficient, local Nusselt number and entropy generation number. The results illustrate that selecting alumina and copper as the nanoparticle leads to the minimum and maximum amounts of skin friction coefficient value, and also copper and titania nanoparticles have the largest and lowest local Nusselt number. Moreover, it is observed that the magnetic parameter has a decreasing effect on both skin friction coefficient and local Nusselt number and an increasing effect on entropy generation number. In addition, our computation shows that all three quantities of skin friction coefficient, local Nusselt number and entropy generation number are the increasing functions of spin parameter. Finally, this simulation represents the feasibility of using magnetic rotating body drives in novel nuclear space propulsion engines and this model has important applications in heat transfer enhancement in renewable energy systems and industrial thermal management.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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