TS-29

　

Performance of Water Droplet Separators

　

Hideaki SUGITA^*, Takeshi NAKAZAWA^*, Tao XU^*, Toshihiro OSARAKAWA^*

　

ABSTRACT

In this paper, the separation performance of the following three kinds of water droplet separators is described. The first one is the eliminator, which is constructed by thin plates bent to make zigzag flow passages. In this eliminator the water droplets entrained in the air-flow are collected by inertial force in the zigzag flow passages, and the performance is also estimated by using the equation of motion of a droplet. The second is the separator by Coulomb force, which is based on the principle of the electrostatic precipitator with the positive and negative poles. From the equation of motion of a droplet, the performance is estimated. For the both separators, the experiments are carried out using air and water, and the experimental and theoretical results are compared.

The third is the wire-mesh demister, which is constructed by galvanized iron wires. For this wire-mesh demister the experiments are carried out and the performance obtained is estimated such as the effect of the number of the layer et al.

Finally, the characteristics of these separators are reciprocally compared.

　

Key Words: Phase Separator, Steam Power Plant, Mist flow, Electric Field Intensity, Coulomb Force

　

NOMENCLATURE

a:Specific surface area of demister

C_D:Drag coefficient

D_P:Droplet diameter

D:Wire diameter

E^*:Electric field intensity in free space

E_O:Average electric field intensity in free space

E:Electric field intensity

F:Coulomb Force

F_D:Drag force

f:Frictional force of the air current and a water droplet

g:Acceleration of gravity

L: Practical length of the test section

l: Bent plate length

m_P:Mass of a water droplet (=πD_P³ρ_P/6),

N: Number of layer aud bending

P: Gap between plates

P₁: Relative projected area of demister

q_∞: Saturation charge of a water droplet

q: Practical electrical charge of a water droplet

r: Radius of center electrode wire

r₀: Radius of a water droplet

R_ep: Droplet Reynolds number

R: Radius of the test section

t: Moving time of a water droplet

t₀: Temperature of air and a water droplet

U: Average velocity of air approaching the inlet of separator

u_a, u_p:Velocity of air aud droplet respectively,

V: Voltage

V₀:Mean velocity of a water droplet in Y direction

x, y: Cartesian coordinate.

ρ_a, ρ_p: Density of air and droplet respectively

ε: Void fraction of demister

ε(x): Practical dielectric constant in the test section

ε^*: Mean dielectric constant in the test section

ε₀: Dielectric constant in free space(=8.85×10^-12 F/m)

ε₁: Dielectric constant of pure water (=1.0126, 110℃ 1.0atm)

ε₂: Dielectric constant of dry air (=1.000, 59, 0℃ 1.0atm)

ε₃: Dielectric constant of water (=80, 20℃)

η: Separation efficiency

η_dn: Fractional separation efficiency

θ: Bending angle

ν_a: Kinematic viscosity of air

　

1. INTRODUCTION

　

Entrainment of water droplets into a gas or steam flow is a phenomenon frequently experienced not only in marine power plants but also in various industrial ones. These entrained droplets generally cause damage or qualitative deterioration of machinery. For example, water droplets from the steam drum of a boiler cause the erosion and corrosion of steam turbine blades; droplets entrained in the intake air of a marine gas turbine has unfavorable effects upon the performance of the turbine.

　

*Kobe University of Mercantile Marine

5-1-1 Fukae Minamimachi Higasinadaku,Kobe 658-0022 JAPAN,

FAX:+81-78-31-6367,E-mail:sugita@cc.kshosen.ac.jp

　

　

　

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