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Coupled heat and mass transfer in absorption of water vapor into Libr-H2o solution flowing on finned inclined surfaces

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Abstract

The absorption characteristics of water vapor into a LiBr-H2O solution flowing down on finned inclined surfaces are numerically investigated in order to study the absorbing performances of different surface shapes of finned tubes as an absorber element. A three-dimensional numerical model is developed. The momentum, energy, and diffusion equations are solved simultaneously using a finite difference method. In order to obtain the temperature and concentration distributions, the Runge-Kutta and the Successive over relaxation methods are used. The flat, circular, elliptic, and parabolic shapes of the tube surfaces are considered in order to find the optimal surface shapes for absorption. In addition, the effects of the fin intervals and Reynolds numbers are studied. The results show that the absorption mainly happens near the fin tip due to the temperature and concentration gradient, and the absorbing performance of the parabolic surface is better than those of the other surfaces.

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Abbreviations

A:

Flow cross-sectional area of LiBr-H2O solution [m2]

a:

Half of fin interval [m]

C:

LiBr concentration

Cp :

Specific heat of LiBr-H2O solution [J/kg ·K]

D:

Diffusion coefficient ofH 2 O [m 2/s]

Dh :

Hydraulic diameter [m]

h:

Heat of absorption [j/kg]

l:

Flow length of z direction [m]

n”:

Average mass flux of the absorbed water vapor at the interface per unit surface area projected on the x-z plane [kg/m 2 s]

ΔP:

Pressure difference between two fluids on the wall [N/m2]

Pr:

Prandtl number, v/a

q”:

Heat flux accompanied with the phase change [j/m2s]

q”w :

Average heat flux at the wall per unit surface area projected on the x-z plane [j/m 2 s]

R:

Radius of curvature of interface (free surface) [m]

Re:

Reynolds number,\(\bar w\)Dh/v

Sc:

Schmidt number, v/D

T:

Temperature [°C]

t:

Effective thickness of LiBr-H2O [m]

u, v, w:

Velocities of the x, y, and z components [m/s]

a:

Thermal diffusivity of solution [m 2/s]

Г:

Mass flow of solution [kg/s]

v:

Kinematic viscosity of solution [m/s]

φ:

Inclined angle [°]

θ:

Contact angle [°]

ρ:

Density of solution [kg/m2]

γ:

Coefficient of surface tension [N/m]

e:

Interfacial

b:

Cross-sectional

w:

Wall

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Authors and Affiliations

  1. Department of Mechanical Engineering, Inha University, 253, Yonghyundong, Namgu, 402-751, Inchon, Korea

    Taebeom Seo & Eunjun Cho

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  1. Taebeom Seo
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  2. Eunjun Cho
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Correspondence to Taebeom Seo.

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Seo, T., Cho, E. Coupled heat and mass transfer in absorption of water vapor into Libr-H2o solution flowing on finned inclined surfaces. KSME International Journal 18, 1140–1149 (2004). https://doi.org/10.1007/BF02983288

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  • DOI: https://doi.org/10.1007/BF02983288

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