Uniform Mass Injection Research Articles

Effects of Cross Jet on Turbulent Main Stream Flow in A Non-Circular Elbow – A Numerical Approach

The performance of fluid transportation model through non-circular elbow ducts with wall mass injection in predicting the velocity and pressure fields is important in Industrial applications. The present work pertains to the two-dimensional numerical analysis of the developing turbulent fluid flow with uniform mass injection through the top wall of a rectangular elbow. A numerical experimentation using control volume formulation considering standard k   turbulence model has been conducted to study different parameters like the velocity distributions, size and shape of the recirculation bubble as well as the friction factor etc. The size and strength of the recirculation bubbles generated in the bend regions are affected by the continuous entry of mass injected through the wall of the elbow. The results show that the velocity field, reattachment points, friction factor etc. are influenced by the side mass injection. The recirculation bubble has been observed to diminish in size by the injection of mass with corresponding changes in the velocity and the friction factors.

Non-premixed swirl-type tubular flames burning liquid fuels

Tubular flames represent a canonical combustion configuration that can simplify reacting flow analysis and also be employed in practical power generation systems. In this paper, a theoretical model for non-premixed tubular flames, with delivery of liquid fuel through porous walls into a swirling flow field, is presented. Perturbation theory is used to analyse this new tubular flame configuration, which is the non-premixed equivalent to a premixed swirl-type tubular burner – following the original classification of premixed tubular systems into swirl and counterflow types. The incompressible viscous flow field is modelled with an axisymmetric similarity solution. Axial decay of the initial swirl velocity and surface mass transfer from the porous walls are considered through the superposition of laminar swirling flow on a Berman flow with uniform mass injection in a straight pipe. The flame structure is obtained assuming infinitely fast conversion of reactants into products and unity Lewis numbers, allowing the application of the Shvab–Zel’dovich coupling function approach.

Pseudo 3D modeling of suction and injection effects on fully developed laminar flow and heat transfer in rectangular fuel cell channels

In this paper, the flow in the rectangular fuel cell channel with different aspect ratios has been numerically simulated. The bottom wall of the rectangular channel is porous and subjected to a uniform mass injection or suction, while the other three walls are nonporous or impermeable. Assuming the hydro-dynamically and thermally fully developed flow, the mass, momentum, and energy equations have been solved with a two-dimensional code. The present numerical results are in good agreement with the numerical results in the literature. The wall friction coefficients and Nusselt numbers were obtained for different aspect ratios, different wall Reynolds numbers (for suction and injection), and different thermal boundary conditions. The results show that for each aspect ratio, friction coefficient ( fRe) is larger for injection than for suction. Also at unit expect ratio, a/ b = 1, the fRe have minimum value for each wall Reynolds number ( Rem) and with increasing and decreasing aspect ratio, fRe increases. The changes of Nusselt ( Nu) number with Rem and aspect ratio is dependent on the thermal boundary conditions and definition of Nu number (for combined boundary condition).

Growth and detachment of carbon dioxide bubbles on a horizontal porous surface with a uniform mass injection

Growth and detachment of carbon dioxide bubbles on a horizontal porous surface in water is investigated in this paper. Uniform carbon dioxide injection on the porous surface is considered. The Young–Laplace equation is solved with the geometry method to yield the bubble shape. The dynamic pressure on the bubble surface due to bubble expansion is neglected. Multi-solution modes are found. Based on the characteristics of the solution modes, it is postulated that the bubble grows with a monotonically increasing base area until the maximum value is reached according to the fundamental solution mode. After that, the bubble jumps toward the secondary solution mode at a constant volume, and then detaches from the surface. The increasing rate of the bubble volume due to mass diffusion/convection is evaluated by solving the momentum and concentration equations. Evolution of the bubble shape then is determined corresponding to the variation of the bubble volume. The numerical results indicate that hydrophobic surface produces large bubble and thus gives rise to better efficiency for dissolved gas removal.

Simulation of fully developed laminar heat and mass transfer in fuel cell ducts with different cross-sections

The fully developed laminar flow and heat transfer for ducts with rectangular and trapezoidal cross-section in fuel cells have been numerically simulated with one porous wall with a uniform mass injection or suction, the other three walls being impermeable. The new concept of thermal boundary conditions of combined constant heat flux and constant temperature on the walls was implemented. Based on the constant thermal–physical property assumption, the wall friction factor and Nusselt number for different mass transfer rates, the aspect ratios and base angles are obtained. Comparisons of these numerical results with published data are also presented.

Numerical analysis of heat and mass transfer from a sphere with surface mass injection or suction.

Numerical analyses for heat and mass transfer of a solid sphere without and with uniform, sinusoidal and evaporative mass injection or suction were made by use of a finite difference method for Rep = 1-200, Pr or Sc = 0.5-2 and φ= -0.2-0.5. Numerical results for the case without mass injection or suction showed good agreement with the results of previous workers. Heat and mass transfer rates with uniform mass injection or suction were found to be affected by Rep and Pr or Sc as well as mass injection ratio, φ. New correlations for the effect of mass injection or suction on heat and mass transfer rates for the case with uniform and sinusoidal mass injection or suction in terms of transfer number were proposed. Heat and mass transfer rates with sinusoidal mass injection or suction showed good agreement with those for evaporative mass injection or suction.

Numerical analysis of the effect of mass injection or suction on drag coefficients of a sphere.

The Navier-Stokes equation for a flow around a sphere with and without uniform mass injection or suction was solved numerically by a finite difference method for Reynolds numbers from 1 to 200 and injection or suction ratios from - 0.2 to 0.5. The predicted drag coefficients for the case without mass injection showed good agreement with the results of previous workers. The effects of uniform mass injection or suction on flow field around a sphere and on skin friction drag and form drag were investigated for low to intermediate Reynolds number ranges. A new correlation for the effects of mass injection or suction on drag coefficients of a solid sphere is proposed.

Laminar flow in a porous tube with uniform mass injection

Laminar flows in a cylindrical porous tube with uniform mass injection through the porous wall are studies. The full Navier-Stokes equations are solved numerically by employing some finite-difference schemes. Solutions for velocity profiles and frictional pressure drops are obtained by the use of vorticity and stream function approach. The results indicate: 1) The fully developed velocity profiles do exist after a certain distance downstream. 2) The radial velocities near the tube wall are greater than the injection velocity at the tube wall due to the requirement of mass conservation. 3) Mass injection through the porous tube wall increases the frictional pressure drop of the flow, and the frictional pressure drop increases with increasing mass injection.

Laminar flow in a porous tube with uniform mass injection

Laminar flow in a porous tube with uniform mass injection

Two-Phase Mach Numbers in Heat Pipe Analysis

E analyzing one-dimensional flow of a compressible two-phase ixture in a heat pipe of constant vapor passage diameter D, Levy uses several plausible assumptions to obtain approximate digital integration of his equations. His solutions suggest without explicit proof infinite gradients in various properties at the downstream end of the evaporator. In this paper the gradients are re-examined after transforming them in terms of an equilibrium two-phase Mach number. It is then shown that the assumption of a uniform mass injection rate me = nDpgVn, where Vn is the radial mass injection velocity, apparently leads to infinite gradients; however, second law analysis rules out a constant me as well as a uniform heat addition rate per unit length of evaporator, Qe = me(hfg + Vn/2), leaving the gradients indeterminate. The subscripts / and g denote liquid and vapor phases.

Slug flow heat transfer with mass injection and linearly varying wall temperature

AbstractThe purpose of this study was to determine the two‐dimensional temperature field for a fluid in slug flow through tubes with uniform mass injection and linearly decreasing wall temperature. A series solution was obtained, the first ten eigenvalues for which were determined from the characteristic equation by the method of Runge‐Kutta. Expressions for local conductive heat flux at the tube wall and local Nusselt number were obtained as a function of inlet Peclet number, injection Peclet number, tube radius, temperature boundary conditions, and fluid properties. Sample results are presented for several injection rates at different wall temperature conditions. In general, mass injection was found to decrease the local heat flux and increase temperature driving force causing a decrease in the Nusselt number.

Experimental Studies of Turbulent Flow in a Porous Circular Tube With Uniform Fluid Injection Through the Tube Wall

Fully developed turbulent flow of air at Re = 28,000 to 82,000 entered a porous tube with circular cross section. Air was injected uniformly through the tube wall for 18 diameters at various ratios of mass velocity through the tube wall to the average mass velocity at the entrance cross section of the tube, ranging from 0.00246 to 0.0584. Tests were also made with zero entrance velocity at the upstream end of the porous tube so that the flow developed in the tube exclusively as a result of the uniform mass injection through the tube wall. Most of the change in the shape of the velocity profiles, in the internal and wall shear, in the momentum flux factor, and in the friction factor occurred within the first 10 to 12 diameters of the tube length. Some changes even persisted further downstream, caused by the fact that mass is continuously injected along the porous tube. The parameters mentioned above, however, become independent of axial position for normalized distances downstream from the entrance cross section larger than x/D = 10 to 12, when they are considered as function of the ratio of injection velocity to average main flow velocity at the specific axial location. Eddy diffusivity values agreed in this presentation reasonably with the results of measurements in turbulent tube flow without injection. Normalized friction factors agreed with values measured in external flow. Properly normalized velocity defect profiles with injection agreed with those for flow without injection.