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Enhancement of the air ejector performance: primary nozzle and mixing chamber investigation

Technical Paper
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Abstract

Air ejectors are, practically, applicable devices used to remove air following a membrane integrity test (MIT). In the present work, investigations of the influence of geometrical parameters on the air ejector performance are performed numerically. Simulations have been performed by solving the steady compressible two-dimensional Reynolds-averaged Navier–Stokes together with realizable k-ε turbulence model equations. A comparison of the computed results with the published experimental data exhibits agreement in terms of entrainment ratio. Increasing amount of the air that should be removed (secondary flow) and reducing energy consumption (primary flow) are considered in this work. To achieve these issues, the effects of geometrical parameters include mixing tube diameter, length of mixing tube, and primary nozzle diameter as well as operation condition which consists of primary flow pressure on the air ejector performance which are all studied. The results show that these changes could improve the entrainment ratio; it means that the secondary flow is increased or the primary flow is decreased. The optimal range of entrainment ratio for specific values of the primary nozzle diameter declares that the air ejector operates at its highest performance.

Keywords

Air ejector Membrane integrity test Mixing tube diameter Primary nozzle diameter Entrainment ratio 

Abbreviations

English letters

A

Section area (m2)

D

Diameter (m)

E

Total energy (J)

k

Thermal conductivity (W/m K)

\(\dot{m}\)

Mass flow rate (kg/s)

P

Static pressure (Pa)

\(P_{\text{p}}\)

Primary pressure (Pa)

\(P_{\text{s}}\)

Secondary pressure (Pa)

r

Radial coordinate (m)

T

Static temperature (K)

u

Velocity components (m/s)

x

Independent variable (_)

y

Dependent variable (_)

z

Axial coordinate (m)

CR

Compression ratio (dimensionless)

ER

Entrainment ratio (dimensionless)

Greek letters

α

Converging angle (deg)

σk

Turbulence kinetic energy \((m^{2} /s^{2} )\)

σε

Turbulence dissipation rate \((m^{2} /s^{3} )\)

ρ

Density \((kg/m^{3} )\)

θ

Coordinate (deg)

μ

Dynamic viscosity (Pa s)

Cε2

Turbulence constant

Subscripts

d

Diffuser flow (_)

p

Primary flow (_)

s

Secondary flow (_)

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Copyright information

© The Brazilian Society of Mechanical Sciences and Engineering 2018

Authors and Affiliations

  1. 1.Department of Mechanical EngineeringHakim Sabzevari UniversitySabzevarIran
  2. 2.Department of Mechanical and Energy EngineeringShahid Beheshti UniversityTehranIran

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