A Study on the Convective Mass Transfer of Nitrogen to Water for a Gas Pressurizing System

2008 ◽  
Author(s):  
Kyoungwoo Seo ◽  
Young-In Kim ◽  
Jae-Kwang Seo ◽  
Doo-Jeong Lee
Keyword(s):  
Mass Transfer ◽  
Boundary Condition ◽  
Natural Convection ◽  
Research Work ◽  
Ideal Gas ◽  
Convective Mass Transfer ◽  
Field Function ◽  
Concentration Difference ◽  
Fluent Simulation ◽  
Fluent 6.3

Mass transfer due to a concentration difference of nitrogen can occur in a nuclear system. Our research work seeks to analyze and understand the mass transfer phenomena of nitrogen in water under the condition of a natural convection using the commercially available CFD computer model, FLUENT 6.3. The maximum solubility was employed to express the boundary condition at an interface between the nitrogen and water. First, the case that nitrogen was transferred to water by only a diffusion was simulated to verify the application of the UDS (User defined scalar) model in FLUENT 6.3 for a mass transfer. Diffusion equation, which was described as a PDE (Partial Differential Equation) with non-homogeneous boundary conditions, was solved and the solved results of the PDE showed a good agreement with those of the FLUENT simulation in the same condition. The same cylinder geometry with that of the diffusion case was used to estimate the convective mass transfer. By the natural convection caused by the thermal boundary condition, the mass transfer of nitrogen had a convection effect. The result of FLUENT 6.3 to compute the convective mass transfer showed that the nitrogen was transferred simultaneously in the entire region by the convection effect and it took about several hours until the mole fraction of nitrogen in the water side reached 50% of the maximum saturated value. The averaged mass transfer coefficient was calculated and compared with the results obtained from the heat and mass transfer analogy. The calculated coefficients showed the lower value than those obtained from the various correlations. When the steam mass transfer toward the gas side was negligible, the pressure drop of the gas side due to the reduced nitrogen caused by a mass transfer was computed using the ideal gas law and the Custom Field Function model in the FLUENT 6.3.

scholarly journals Effective diffusivity and convective mass transfer coefficient during the drying of bananas

2012 ◽  
Vol 32 (2) ◽  
pp. 342-353 ◽  
Author(s):  
Cleide M. D. P. da S. e Silva ◽  
Wilton P. da Silva ◽  
Vera S. de O. Farias ◽  
Josivanda P. Gomes
Keyword(s):  
Experimental Data ◽  
Mass Transfer ◽  
Boundary Condition ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Effective Diffusivity ◽  
Convective Boundary Condition ◽  
Drying Kinetics ◽  
Convective Mass Transfer ◽  
Convective Boundary

In this article, a methodology is used for the simultaneous determination of the effective diffusivity and the convective mass transfer coefficient in porous solids, which can be considered as an infinite cylinder during drying. Two models are used for optimization and drying simulation: model 1 (constant volume and diffusivity, with equilibrium boundary condition), and model 2 (constant volume and diffusivity with convective boundary condition). Optimization algorithms based on the inverse method were coupled to the analytical solutions, and these solutions can be adjusted to experimental data of the drying kinetics. An application of optimization methodology was made to describe the drying kinetics of whole bananas, using experimental data available in the literature. The statistical indicators enable to affirm that the solution of diffusion equation with convective boundary condition generates results superior than those with the equilibrium boundary condition.

Entropy Generation in Convective Heat Transfer and Isothermal Convective Mass Transfer

1987 ◽  
Vol 109 (3) ◽  
pp. 647-652 ◽  
Author(s):  
J. Y. San ◽  
W. M. Worek ◽  
Z. Lavan
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Boundary Conditions ◽  
Convective Heat Transfer ◽  
Heat And Mass Transfer ◽  
Convective Heat ◽  
Entropy Generation ◽  
Ideal Gas ◽  
Convective Mass Transfer ◽  
Plate Spacing

The irreversible generation of entropy for two limiting cases of combined forced-convection heat and mass transfer in a two-dimensional channel are investigated. First, convective heat transfer in a channel with either constant heat flux or constant surface temperature boundary conditions are considered for laminar and turbulent flow. The entropy generation is minimized to yield expressions for optimum plate spacing and optimum Reynolds numbers for both boundary conditions and flow regimes. Second, isothermal convective mass transfer in a channel is considered, assuming the diffusing substance to be an ideal gas with Lewis number equal to unity. The flow is considered to be either laminar or turbulent with boundary conditions at the channel walls of either constant concentration or constant mass flux. The analogy between heat and mass transfer is used to determine the entropy generation and the relations for optimum plate spacing and Reynolds number. The applicable range of the results for both limiting cases are then investigated by non-dimensionalizing the entropy generation equation.

Combined Heat and Mass Transfer by Natural Convection in a Vertical Enclosure

1987 ◽  
Vol 109 (1) ◽  
pp. 104-112 ◽  
Author(s):  
O. V. Trevisan ◽  
A. Bejan
Keyword(s):  
Mass Transfer ◽  
Natural Convection ◽  
Heat And Mass Transfer ◽  
Lewis Number ◽  
Convective Mass Transfer ◽  
Transfer Rates ◽  
Rectangular Slot ◽  
Transfer Path ◽  
Mass Fluxes ◽  
Buoyancy Ratio

The phenomenon of natural convection caused by combined temperature and concentration buoyancy effects is studied analytically and numerically in a rectangular slot with uniform heat and mass fluxes along the vertical sides. The analytical part is devoted to the boundary layer regime where the heat and mass transfer rates are ruled by convection. An Oseen-linearized solution is reported for tall spaces filled with mixtures characterized by Le = 1 and arbitrary buoyancy ratios. The effect of varying the Lewis number is documented by a similarity solution valid for Le >1 in heat-transfer-driven flows, and for Le <1 in mass-transfer-driven flows. The analytical results are validated by numerical experiments conducted in the range 1≤H/L≤4, 3.5×105≤Ra≤7×106, −11≤n≤9, 1≤Le≤40, and Pr=0.7, 7. “Massline” patterns are used to visualize the convective mass transfer path and the flow reversal observed when the buoyancy ratio n passes through the value −1.

Natural Convection Heat and Mass Transfer in the Vertical Cylindrical Porous Channel Under the Effects of Time-Periodic Boundary Condition

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Hayder I. Mohammed ◽  
Donald Giddings
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Boundary Condition ◽  
Porous Medium ◽  
Nusselt Number ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Aspect Ratio ◽  
Heat And Mass Transfer ◽  
Vertical Wall

Abstract Heat and mass transfer are investigated numerically with steady-state laminar natural convection through a vertical cylindrical enclosure filled with a liquid-saturated porous medium. The vertical wall is under a constant magnetic field and various durations of periodic heating boundary condition; the top and bottom surfaces are kept at a constant cold temperature. Continuity, momentum, and energy equations are transformed to dimensionless equations. The finite difference approach with the line successive over-relaxation (LSOR) method is used to obtain the computational results. This study covers the heat transfer, the temperature distribution, and the velocity field in the domain under the variation of different parameters. The code used is validated by modifying it to analyze the Nusselt number in the existing experimental literature of Izadpanah et al. (1998, “Experimental and Theoretical Studies of Convective Heat Transfer in a Cylindrical Porous Medium,” Int. J. Heat Fluid Flow, 19(6), pp. 629–635). This work shows that Nusselt number decreases (with varying gradient) as the aspect ratio increases, and that it increases as the Rayleigh number increases. The centerline temperature has a proportional relationship with the heating amplitude and the heating period (as the system receives more heat) and is inversely proportional with Rayleigh number. Increasing the Rayleigh number causes increased convective velocity, which affects the position of the hot region, and causes a decrease in the temperature field. Increasing the aspect ratio results in a warm stream at the center of the cylinder, and when the time period of the heating increases, the circulation becomes faster and the intensity of the temperature contour layers decreases. In this work, a correlation for Nu as a function of the mentioned parameters is developed.

Investigation of Solution Growth of SiC by Temperature Difference Method Using Fe-Si Solvent

2013 ◽  
Vol 740-742 ◽  
pp. 31-34 ◽  
Author(s):  
Takeshi Yoshikawa ◽  
Sakiko Kawanishi ◽  
Kazuki Morita ◽  
Toshihiro Tanaka
Keyword(s):  
Mass Transfer ◽  
Growth Rate ◽  
Raman Spectroscopy ◽  
Crystal Growth ◽  
Natural Convection ◽  
Temperature Difference ◽  
Difference Method ◽  
Solution Growth ◽  
Resistance Heating ◽  
Convective Mass Transfer

This paper describes the solution growth of SiC by a temperature difference method using an Fe-Si solvent. Crystal growth of SiC from an Fe-40 mol%Si solvent onto a seed wafer of 6H-SiC or 4H-SiC was carried out at 1623 – 1723 K under induction heating. Homo-epitaxial growth on both 6H-SiC and 4H-SiC was identified by Raman spectroscopy, and the SiC growth rate was found to be 90 – 260 μm/h. Experiments were also conducted under resistance heating at 1623 K using conditions which suppressed natural convection. Convective mass transfer in the solution was found to be important for rapid growth of SiC.

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