Numerical study of the evaporative cooling of liquid film in laminar mixed convection tube flows

Feddaoui, M’barek; Belahmidi, El Mustapha; Mir, A.; Bendou, Abdelaziz

doi:10.1016/s1290-0729(01)01286-8

Cited by 46 publications

(21 citation statements)

References 16 publications

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“…Kim and Ferreira [15] proposed a new method to determine heat and mass transfer coefficients from experimental data. Feddaoui et al [16] reported a numerical model to investigate the evaporative cooling of liquid film falling along a vertical tube. Results showed that a better liquid film cooling was noticed for a system having a higher inlet liquid temperature, a higher gas flow Reynolds number or a lower liquid flow rate.…”

Section: Abbreviationsmentioning

confidence: 99%

Numerical study of heat and mass transfer of ammonia-water in falling film evaporator

Huang

2011

Heat Mass Transfer

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To investigate the performance of the heat and mass transfer of ammonia water during the process of falling film evaporation in vertical tube evaporator, a mathematical model of evaporation process was developed and solved based on stream function. Then an experimental study of falling film evaporation was carried out in order to validate the mathematical model. A series of parameters, such as velocity, film thickness and concentration, etc., were obtained from the mathematical model. The calculated results show that the average velocity and the film thickness change sharp at the entrance region when x \ 100 mm, while they vary slightly in the fully developed region when x [ 100 mm. The film thickness depends largely on the flow rate of solution. It is observed that the heating power and mass flow of solution significantly affect the concentration difference between the inlet and outlet of evaporation tube. The calculated results reveal that the tube length has a significant impact on the amounts of ammonia vapor evaporated. It is suggested that the roll-worked enhanced tube should be used in order to decrease the concentration gradient in the film thickness direction and enhance the heat and mass transfer rate. Furthermore, the experimental and calculated results indicate that the inlet solution concentration has a great influence on the heat exchange capacity, the amounts of ammonia vapor evaporated and the evaporation pressure. AbbreviationsC P Specific heat, J kg -1 K -1 D Tube diameter, m D m Diffusion coefficient, m 2 /s H Specific enthalpy, J/kg L Tube length, m m Solution mass flow, kg/h mE The amount of evaporated ammonia vapor, kg/h _ m Evaporation rate, kg/s/m 2 N Sequence number of experiment P Evaporating pressure, kPa PE Percent of evaporated ammonia vapor, % Q Heat exchange capacity between hot water and solution, kW T Temperature,°C u Film velocity of x direction, m/s v Film velocity of y direction, m/s V Volumetric flow of water, L/h DH Enthalpy difference, J/kgGreek symbols n Mass concentration of solution, kg/kg d Film thickness, m U Spray density, kg m -1 s -1 l Dynamic viscosity, N s/m 2 q Density, kg/m 3 k Thermal conductivity, W m -1 K -1

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Section: Abbreviationsmentioning

confidence: 99%

Numerical study of heat and mass transfer of ammonia-water in falling film evaporator

Huang

2011

Heat Mass Transfer

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“…A great enhancement in heat transfer due to the exchange of latent heat with phase changes was found. Some numerical investigations of liquid film evaporation were then carried out for fluid flows along inclined plates, coaxial cylinders, and vertical tubes . The authors showed that the thermal transfer is dominated by the latent heat transfer at the liquid‐air interface.…”

Section: Introductionmentioning

confidence: 99%

Analysis of conjugated processes of film evaporation and condensation in a tubular heat exchanger

2016

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This paper investigates coupled phase changes by forced convection from co‐current flows of liquid films and vapour‐air mixtures in a tubular heat exchanger. Evaporation occurs in the inner tube and condensation in the annulus region. Heat and mass transfers in the liquid films and the vapour‐gas mixtures are described by the conservation equations of momentum, energy, and diffusion. An appropriate change of coordinates is introduced in order to obtain a computational mesh with straight liquid‐mixture interfaces along the walls. The governing equations are discretized by an implicit finite differences method and solved using an efficient numerical methodology. The distributions of axial velocity, temperature, and vapour concentration in all regions of the tubes are determined from iterative procedures with a high convergence rate. The current analysis also provides the axial evolutions of film thicknesses, heat flux, condensation, and evaporation rates in the whole domain. In addition, the effects of the inlet parameters of Reynolds number, relative humidity, pressure, and liquid flow rate on the heat transfer characteristics, and the evaporation and condensation rates are also investigated.

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“…They observed that the evaporative cooling disturbs considerably the velocity and temperature profiles in particular near the exit section of the channel. Feddaoui and his co-workers [8,9] studied the thermal transfer taking place in the event of film evaporation in the presence of a gas flow inside a vertical heated tube. They reported that the evaporation is higher for a smaller inlet liquid flow and a larger heat flux through the wall.…”

Section: Introductionmentioning

confidence: 99%

Numerical study of the evaporation by mixed convection of ethanol in partially heated plate along a vertical channel

Alla

Feddaoui

Meftah

2015

International Journal of Heat and Mass Transfer

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Numerical study of the evaporative cooling of liquid film in laminar mixed convection tube flows

Cited by 46 publications

References 16 publications

Numerical study of heat and mass transfer of ammonia-water in falling film evaporator

Numerical study of heat and mass transfer of ammonia-water in falling film evaporator

Analysis of conjugated processes of film evaporation and condensation in a tubular heat exchanger

Numerical study of the evaporation by mixed convection of ethanol in partially heated plate along a vertical channel

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