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Heat and Mass Transfer

, Volume 51, Issue 12, pp 1747–1760 | Cite as

Simultaneous heat and mass transfer inside a vertical channel in evaporating a heated falling glycols liquid film

  • Abderrahman Nait Alla
  • M’barek FeddaouiEmail author
  • Hicham Meftah
Original

Abstract

The interactive effects of heat and mass transfer in the evaporation of ethylene and propylene glycol flowing as falling films on vertical channel was investigated. The liquid film falls along a left plate which is externally subjected to a uniform heat flux while the right plate is the dry wall and is kept thermally insulated. The model solves the coupled governing equations in both phases together with the boundary and interfacial conditions. The systems of equations obtained by using an implicit finite difference method are solved by Tridiagonal Matrix Algorithm. The influence of the inlet liquid flow, Reynolds number in the gas flow and the wall heat flux on the intensity of heat and mass transfers are examined. A comparison between the results obtained for studied glycols and water in the same conditions is made. The results indicate that water evaporates in more intense way in comparison to glycols and the increase of gas flow rate tends to improve slightly the evaporation.

Keywords

Heat Flux Liquid Film Propylene Glycol Mixed Convection Local Nusselt Number 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of symbols

CP

Specific heat (J kg−1 K−1)

CPa

Specific heat of air (J kg−1 K−1)

CPv

Specific heat of species vapour (J kg−1 K−1)

D

Mass diffusivity (m2 s−1)

Nus

Local Nusselt number of sensible heat transport

Nul

Local Nusselt number of latent heat transport

Nux

Overall Nusselt number

Sh

Interfacial Sherwood number

qSI

Sensible heat flux (W m−2)

qLI

Latent heat flux (W m−2)

qTI

Total heat flux (W m−2)

g

Gravitational acceleration (ms−2)

P

Mixture pressure (Pa)

Pd

Dynamic pressure (Pa)

\(\dot{m}_{I}\)

Evaporating mass flux (kg m−2 s−1)

Re

Reynolds number of the gas stream

ReL

Liquid film Reynolds number

T

Temperature (K)

TI

Gas–liquid interface temperature (K)

Mr

Nondimentional accumulated mass evaporation rate

Ma

Molar mass of air (kg mol−1 K−1)

Mv

Molar mass of vapour (kg mol−1 K−1)

u

Axial velocity (ms−1)

u0

Inlet axial velocity (ms−1)

v

Transversal velocity (ms−1)

w

Mass fraction of vapour

wI

Mass fraction of vapour at gas–liquid interface

x

Coordinate in the flow direction (m)

y

Coordinate in the transverse direction (m)

d

Channel width (m)

Greek symbols

Γ0

Inlet liquid mass flow rate (kg m−1 s−1)

δx

Local liquid film thickness (m)

hfg

Latent heat of vaporisation (J kg−1)

λ

Thermal conductivity (W m−1 K−1)

μ

Dynamic viscosity (kg m−1 s−1)

ν

Kinematics viscosity (m2 s−1)

ρ

Density (kg m−3)

ϕ0

Inlet relative humidity

Subscripts

I

Condition at the gas-liquid interface

G

Mixture (gas + vapour)

L

Liquid film

0

Condition at inlet

v

Vapour

w

Condition at wall

b

Bulk quantity

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Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  • Abderrahman Nait Alla
    • 1
  • M’barek Feddaoui
    • 1
    Email author
  • Hicham Meftah
    • 1
  1. 1.Laboratoire Génie Energie, Matériaux et SystèmesENSA-Ibn Zohr UniversityAgadirMorocco

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