Small Values Of Prandtl Number Research Articles

ТЕПЛООБМЕН В ПЛОСКОМ КАНАЛЕ ПРИ ТУРБУЛЕНТНОМ РЕЖИМЕ ТЕЧЕНИЯ В СЛУЧАЕ МАЛЫХ ЗНАЧЕНИЙ ЧИСЛА ПРАНДТЛЯ ПО ДАННЫМ ПРЯМОГО ЧИСЛЕННОГО МОДЕЛИРОВАНИЯ

Using the results obtained by the method of direct numerical simulation of the heat transfer process in a flat channel by various authors, it is shown that at small values of Prandtl number quite a few characteristics of the heat transfer process in a flat channel depend not on Reynolds and Prandtl numbers separately, but on Peclet number. Peclet number is calculated from the so-called dynamic speed

Optimization of entropy generation in nonlinear stratified Powell–Eyring fluid with convective boundary conditions

Entropy generation phenomenon is applied in reactors, turbines, natural convection, chillers, functional and regular graded materials. Irreversibility of a system and surroundings in Powell–Eyring fluid is analyzed in this research article. Flow is deformed by an inclined sheet. Measure of irreversibility is also called entropy. Rate of Entropy generation is calculated by considering heat transfer, radiation and viscous dissipation phenomena. Thermal stratification (nonlinear) and heat generation/absorption are incorporated in heat transport while solutal stratification (nonlinear) and chemical reaction have taken part in mass transport. Mixed convection phenomenon is also accounted here. To obtain the analytical solutions of nonlinear and non-dimensional governing equations homotopic analysis method is applied. The behavior of emerging parameters is discussed comprehensively via velocity, temperature and concentration profile. Entropy generation can be minimized by small values of Prandtl number and Eckert number. Thus, these physical phenomena can be used as a cooling agent in various industrial processes.

Thermal convection in a cylinder and the problem of planform selection in an internally heated fluid layer.

The paper deals with the hexagonal convective flow near the stability threshold in an internally heated fluid layer. In our previous numerical study of convection near the stability threshold in a square box with internal heat generation [Phys. Lett. A 377, 2111 (2013)]PYLAAG0375-960110.1016/j.physleta.2013.06.013 for a region of large horizontal extent, it has been shown that at small values of Prandtl number (Pr), convection sets in as a pattern of hexagonal cells with upward motion in the center (up-hexagons), whereas at large Pr, a stable flow pattern is formed by hexagonal cells with a downward motion in the center (down-hexagons). Here, we study axisymmetric convection in a cylinder as a model of motion in a single hexagonal cell. The radius of the cylinder matches the size of hexagons observed in our three-dimensional simulation. The lateral boundary of the cylinder is free and heat insulated. Horizontal bounding surfaces are rigid. The upper boundary is maintained at a constant temperature; the lower one is insulated. Two stable, steady-state motions with the upward and downward flow at the cylinder axis have been attained in calculations, irrespective of Pr. Cylindrical motion with the same direction of circulation as in the stable hexagons has a maximum temperature drop measured along the radius at the bottom of the cell. We suggest maximization of the temperature drop as a selection criterion, which determines the preferred state of motion in an internally heated fluid layer. This new selection principle is validated by the comparative analysis of the dominant nonlinear effects in low- and high-Prandtl number convection.

Heat Transfer in MHD Visco-elastic Fluid Flow over a Stretching Surface

An analysis has been carried out to study the effect of magnetic field on the visco-elastic fluid flow and heat transfer over a non-isothermal stretching sheet with internal heat generation. The solutions for heat transfer characteristics are evaluated numerically for different parameters such as Prandtl number, magnetic field, suction, visco-elasticity, and the temperature profile. The solutions for the temperature profile, heat transfer characteristics, and their asymptotic limits for large and small Prandtl numbers are obtained in terms of Kummer's function. The important finding is that the effect of visco-elasticity is to decrease temperature profile in the flow field for small values of Prandtl number. The temperature profile decreases with the increase of magnetic field.

Laminar Flow in the Open Thermosyphon, with Special Reference to Small Prandtl Numbers

By use of approximate methods, the rates of heat transfer are predicted for laminar flow due to natural convection in heated vertical cylinders closed at the lower end and opening at the top into a reservoir of cool fluid. Most interest is shown in the flow found for small values of Prandtl number associated with mercury and liquid metals. The type of flow is found to depend upon the Prandtl number as well as the product of the Rayleigh number and radius/length ratio.