Three-dimensional CFD modeling of a steam ejector

ABSTRACT

Steam ejectors are one of the key components of steam ejector refrigeration/heat pump systems. Steam ejector is required to compress low-pressure stream to a higher pressure. Steam ejectors have no moving part, a simple structure, low cost, reliability, easy installation, high vacuum performance, corrosion resistance, and no consumption of electrical energy. In this study, steam ejector design was modeled using finite volume techniques, and Mach number and pressure in constant cross-section have been compared with analytical data reported in the literature. In this work, numerical calculations were performed with ANSYS Fluent(ANSYS FLUENT Theory Guide, ANSYS, Inc. Release 17.2, 2016, Canonsburg, PA, USA), a computational fluid dynamic code. In the turbulent flow, heat transfer-based analyses were performed using energy equations.

KEYWORDS:

• Steam
• ejector
• three-dimensional
• CFD modeling

Nomenclature

d	=	Throat diameter of the primary nozzle
D	=	Diameter of constant section
l1	=	Length of convergent mixing section
l2	=	Length of constant section
l3	=	Length of diffusor section
T	=	Temperature (K)
fj	=	Surface penetration rate in a direction
fv	=	Volumetric porosity rate
fs	=	Superficial penetration rate
R	=	Distribution resistance (N/m3)
S	=	Source term (m/s2)
i, j	=	(= x, y, z) components in the Cartesian coordinate system
u	=	x direction velocity (m/s)
v	=	y direction velocity (m/s)
w	=	z direction velocity (m/s)

Abbreviation

CFD	=	Computational fluid dynamics
RNG	=	Re-normalisation group
SIMPLE	=	Semi-implicit method
Ma	=	Mach number

Greek letters

ρ	=	Fluid density (kg/m3)
ϕ	=	Distribution heat source (W/m3)
ɛ	=	Dissipation rate of turbulent kinetic energy (kg/m s3)
μ	=	Dynamic viscosity (Pa s)
μt	=	Turbulent viscosity (Pa s)
Ɵ1	=	Convergence and divergence angle of the primary nozzle
Ɵ2	=	Angle of convergent mixing section