Unsteady double-diffusive natural convection in a two-sided lid-driven inclined porous enclosure with sinusoidal boundary conditions with Soret and Dufour effects

Unsteady double-diffusive natural convection in an inclined porous enclosure with sinusoidal boundary conditions and Soret and Dufour parameters is studied. The unique aspects of the set-up are that the left vertical and bottom walls are heated and concentrated non-uniformly and uniformly, respectively, while the right vertical wall is well insulated and the top wall is maintained at a constant concentration and cold temperature. A staggered grid finite-difference method is used to solve the system of partial differential equations that model heat and mass transfer inside the enclosure. We demonstrate the effects of the Soret and Dufour parameters and the inclination angle on the unsteady double-diffusive natural convection in the inclined porous enclosure. With all the numerical studies, the least square curve fitting (exponential non-linear curve fitting) of average Nusselt number and average Sherwood number with respect to different Soret and Dufour numbers at the left vertical wall which is non-uniformly heated and concentrated is examined here. Comparison with previously published results shows an excellent agreement.     

Mixed convection heat transfer of a nanofluid in a lid-driven enclosure with two adherent porous blocks

Journal of Thermal Analysis and Calorimetry - Convective flow and heat transfer in an alumina/water nanofluid enclosure having two centered adherent porous blocks under the effect of moving upper...     

Experimental investigation of a water/nanofluid jacket performance in stack heat recovery

Journal of Thermal Analysis and Calorimetry - The effects of nanofluids (Al2O3–water) on the overall thermal performance of an annular enclosure (or jacket) are experimentally investigated...     

Natural convection heat transfer and entropy generation in a porous rhombic enclosure: influence of non-uniform heating

Journal of Thermal Analysis and Calorimetry - In this paper, we present a numerical investigation of natural convection heat transfer and entropy generation for a rhombic enclosure with inclination...     

Exact solution of mass diffusion into a finite volume

A new theoretical based model of mass diffusion from an external constant source, through a membrane, into an enclosure and at a constant temperature is developed. Exact solution is presented of one dimensional transient Fickian diffusion equation with initial and boundary conditions appropriate for the mass diffusion into an enclosure. The present model has many practical applications. It may be used as a working tool in diffusion experiments in selecting membrane materials, saving experimental time and cost, predicting the shelf-life of pre-packaged food, drugs and other vulnerable materials to external effects. A good agreement of the model is shown with existing data. The economic advantage of the present model is illustrated by offering shorter experimental time by an order of magnitude. The use of theoretical results minimizes the exposure time to dangerous concentrations of hazardous materials during the experiments. Analysis of the model provides simple linear relationships between various parameters of the mass diffusion into an enclosure.     

Analysis of unsteady mixed convection of Cu–water nanofluid in an oscillatory,lid-driven enclosure using lattice Boltzmann method

Journal of Thermal Analysis and Calorimetry - The unsteady physics of laminar mixed convection in a lid-driven enclosure filled with Cu–water nanofluid is numerically investigated. The top...     

Use of artificial neural network in forecasting optimal distance of enclosures containing PCM-introduced for improving the performance of the evacuated tube solar collectors

Journal of Thermal Analysis and Calorimetry - In this study, the usefulness of using regression-based methods in estimating the optimal fins distance in a PCM finned enclosure of the evacuated tube...     

A study on the effect of magnetic field and the sinusoidal boundary condition on free convective heat transfer of non-Newtonian power-law fluid in a square enclosure with two constant-temperature obstacles using lattice Boltzmann method

Journal of Thermal Analysis and Calorimetry - In this paper, the flow pattern and thermal characteristics of free convection of a Newtonian magnetohydrodynamic fluid flow inside a square enclosure...     

Using artificial neural network to optimize the flow and natural heat transfer of a magnetic nanofluid in a square enclosure with a fin on its vertical wall: a lattice Boltzmann simulation

Journal of Thermal Analysis and Calorimetry - The heat transfer of a nanofluid in a square enclosure is numerically simulated using FORTRAN software in this paper, by considering the radiation...     

MHD free convection heat transfer of a water–Fe3O4 nanofluid in a baffled C-shaped enclosure

Journal of Thermal Analysis and Calorimetry - In this paper, the effect of a baffle on free convection heat transfer of a water–Fe3O4 nanofluid in a C-shaped enclosure in the presence of a...     

Bioconvection in oxytactic microorganism-saturated porous square enclosure with thermal radiation impact

This investigation addresses bioconvection of oxytactic microorganisms in a porous square enclosure by thermal radiation impact. The bioconvection flow and heat transfer in porous media are formulated based on Darcy model of Boussinesq approximation. Appropriate transformations lead to the non-dimensionalized governing partial differential equations. Galerkin finite element method for the resulting equations is computed. The role of relevant parameters on the streamlines, isotherms, isoconcentrations of oxygen and microorganisms and average Nusselt number is analysed in the outputs. It is revealed that the flow intensity of bioconvection is pronounced with larger Rayleigh number and reduced with radiation parameter. Furthermore, the temperature distribution is affected significantly with Rayleigh number. Radiation parameter serves to fasten the heat transfer in the enclosure. Oxygen density is enhanced with Rayleigh number and radiation parameter. The profile of motile isoconcentrations is boosted with Rayleigh number. The stability of microorganisms is improved with the radiation parameter.

     

Shape fluctuation-induced dynamic hysteresis

We consider a system of Brownian particles confined in a two-dimensional bilobal enclosure whose walls are driven in time periodically by an external perturbation. The response of the particles under shape modulation is characterized by a relaxational delay which results in a non-vanishing area of the response function-field loop, response function being the integrated probability of residence of the particles in any of the lobes. This phenomenon is an entropic analogue of dynamical hysteresis, which vanishes in the quasi-static limit. The hysteresis loop area depends on temperature, strength of modulating field, and the geometrical parameters of the enclosure and exhibits a turnover as a function of frequency of the field.     

The Baffle Length Effects on the Natural Convection in Nanofluid-Filled Square Enclosure with Sinusoidal Temperature

The proper process of applying heat to many technological devices is a significant challenge. There are many nanofluids of different sizes used inside the system. The current study combines this potential to improve convection effects, considering numerical simulations of natural convection using Cu/water nanofluids in a square enclosure with bottom blocks embedded in baffles. The enclosure consists of two vertical walls with isothermal boundary conditions; the left wall is the sinusoidal heat source, whereas the right wall is cooled. The investigations dealt with the influences of nanoparticle concentration, Rayleigh number, baffle length, and thermal conductivity ratioon isotherms, stream functions, and average Nusselt number. The results present that, when the Rayleigh number rises, the fluid flow velocity increases, and the heat transfer improves. Furthermore, the baffle length case (L_b = 0.3) provides higher heat transfer characteristics than other baffle height cases.     

Thermal analysis of the RFX-mod2 operating conditions for the design of the temperature measurement system

Journal of Thermal Analysis and Calorimetry - The laminar two-dimensional mixed convection in a trapezoidal enclosure with a rotating inner circular cylinder and a sinusoidal bottom wall is studied...     

Non-Darcian natural convection of a nanofluid due to triangular fins within trapezoidal enclosures partially filled with a thermal non-equilibrium porous layer

Journal of Thermal Analysis and Calorimetry - Numerical simulations for the convective transport due to triangular fins within an inclined trapezoidal enclosure that is filled by a nanofluid layer...     

Magnetic field effects on natural convection flow of a non-Newtonian fluid in an L-shaped enclosure

The effect of magnetic field on natural convection heat transfer in an L-shaped enclosure filled with a non-Newtonian fluid is investigated numerically. The governing equations are solved by finite-volume method using the SIMPLE algorithm. The power-law rheological model is used to characterize the non-Newtonian fluid behavior. It is revealed that heat transfer rate decreases for shear-thinning fluids (of power-law index, n?<?1) and increases for shear-thickening fluids (n?>?1) in comparison with the Newtonian ones. Thermal behavior of shear-thinning and shear-thickening fluids is similar to that of Newtonian fluids for the angle of enclosure α?<?60° and α?>?60°, respectively.     

Conjugate natural convection of nanofluids inside an enclosure filled by three layers of solid,porous medium and free nanofluid using Buongiorno’s and local thermal non-equilibrium models

Journal of Thermal Analysis and Calorimetry - The natural convective heat transfer of nanofluids was addressed inside a square enclosure filled by three different layers: solid, porous medium and...     

Natural convection of nanoencapsulated phase change suspensions inside a local thermal non-equilibrium porous annulus

Journal of Thermal Analysis and Calorimetry - In this study, the heat transfer, fluid flow and heat capacity ratio are analyzed in an annulus enclosure filled with porous and saturated by a...     

Hybrid monte carlo method for simulation of two-component aerosol coagulation and phase segregation

The paper presents the development of a hybrid Monte Carlo (MC) method for the simulation of the simultaneous coagulation and phase segregation of an immiscible two-component binary aerosol. The model is intended to qualitatively model our prior studies of the synthesis of mixed metal oxides for which phase-segregated domains have been observed in molten nanodroplets. In our previous works (J. Aerosol Sci.32, 1479 (2001); Chem. Eng. Sci.56, 5763 (2001); submitted for publication) we developed sectional and monodisperse models where the internal state of the aerosol particles was described. These methods have certain limitations and it is difficult to include additional physical effects into the framework. Our new approach combines both constant volume and constant number Monte Carlo methods. Similar to our previous models, we assume that the phase segregation is kinetically controlled. The MC approach allows us to compute the mean number of enclosures (minor phase) per droplet, average enclosure volume, and the width of the enclosure size distribution. The results show that asymptotic behavior of enclosure distribution exists that is independent of initial conditions, which is very close to the continuum self-preserving distribution. Temperature is a key parameter because it allows for a significant change in the internal transport rate within each droplet. In particular, increasing the temperature significantly enhances the Brownian coagulation rate and lowers the number of enclosures per droplet. As a result, the MC results indicate that the growth of the minor phase can be moderated quite dramatically by small changes in system temperature. These results serve to illustrate the utility of this synthesis approach to the controlled growth of nanoparticles through the use of a majority matrix to slow down the encounter frequency of the minor phase and therefore its particle size.     

Efficient evaluation of the effective dielectric function of a macromolecule in aqueous solution

We propose an analytical approach to calculate the effective dielectric function of proteins in aqueous solution. The screening effect if quantified by a measure of enclosure which is based on the distribution of solute atomic volumes around a pair of charges in a macromolecule. For protein conformations that vary significantly in size and shape, a comparison with finite difference Poisson calculations shows that pair interaction energies, their sums and solvation energies are well reproduced. The approach rivals the speed of simple distance dependent dielectric functions and the accuracy of the generalized Born model.