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Direct contact evaporation of a single two-phase bubble in a flowing immiscible liquid medium. Part I: two-phase bubble size

  • Hameed B. MahoodEmail author
  • Ali Sh. Baqir
  • Al-Dunainawi Yousif
  • Anees A. Khadom
  • Alasdair N. Campbell
Original
  • 10 Downloads

Abstract

The evaporation of a single n-pentane drop in another warm flowing liquid (water) medium has been studied experimentally. A Perspex column with an internal diameter of 10 cm and height of 150 cm was used throughout the experiments. N-pentane liquid at its saturation temperature and warm flowing water with flow rate of 10, 20, 30 and 40 L/h were employed as the dispersed and continuous phases, respectively. The active height of the continuous phase in the column (i.e. the level of the continuous phase in the column) covered only 100 cm of the column’s height. A Photron FASTCAM high-speed camera (~ 65,000 f/s) was used to film the evaporation of the drop, while AutoCAD was used to analyse the images from the camera. The diameter ratio (diameter of growing two-phase bubble to initial drop diameter) of the two-phase bubble formed because of the evaporation of the pentane drop in direct contact with the water was measured. Also, the vaporisation ratio (x), the open angle of vapour (β), the total height for complete evaporation and the total evaporation time were measured. The effects of the continuous phase flow rate and the temperature difference between the contacting phases, in terms of Jakob number (Ja), on the measured parameters were investigated. Furthermore, a statistical model to fit the experimental data was developed. The experimental results showed that the diameter of the two-phase bubble is strongly influenced by varying the continuous phase flow rate. The final size of the evaporated vapour bubble was unaffected by the flow rate of the continuous phase, while both the total height required for complete evaporation and hence the time required was significantly influenced. A similar impact was observed for the vaporisation ratio and the open angle of vapour.

Nomenclature

a

Radius of two-phase bubble (m)

D

Diameter of two-phase bubble (m)

Do

Initial diameter of drop (m)

dc

Diameter of column (m)

Cp

Spesific heat of continuous phase (kJ/kg. K.)

Ja

System Jakob number (ρcCp(Tc − Td)/ρdvhfg)

Hv

Total height required for complete evaporation (m)

hfg

Latent heat of evaporation of dispersed phase (kJ/kg)

m

Ratio of liquid to vapour density in the two-phase bubble (kg/m3)

N

Constant appears in Eq. (2)

P1

Constant appears in Eq. (2)

Qc

Volumetric flow rate of continuous phase (m3/s)

Re

Reynolds number

Tc

Temperature of continuous phase (°C)

Td

Saturation temperature of dispersed phase (°C)

U

Velocity of continuous phase (m/s)

VR

Ratio of vapour volume to total volume of tow-phase bubble

Vr

Radial velocity component (m/s)

Vθ

Tangential velocity component (m/s)

x

Vaporization ratio

Greek symbols

β

Half opening angle (rad)

μc

Dynamic viscosity of continuous phase (N. s/m2)

ρc

Density of continuous phase (kg/m3)

ρdL

Density of liquid dispersed phase (kg/m3)

ρdv

Density of vapour dispersed phase (kg/m3)

τ

Dimensionless time

Notes

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of Chemical and Process Engineering, Faculty of Engineering and Physical SciencesUniversity of SurreyGuildfordUK
  2. 2.Engineering Technical CollegeAl-Furat Al-Awsat Technical UniversityAl-NajafIraq
  3. 3.Ministry of Higher Education and Scientific ResearchBaghdadIraq
  4. 4.Department of Chemical Engineering, College of EngineeringUniversity of DiyalaDiyalaIraq

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