Modeling of steam–water direct contact condensation using volume of fluid approach

ABSTRACT

Direct contact condensation (DCC) of steam in subcooled water has paramount importance in many heat transfer devices in different industrial areas like nuclear, thermal, chemical plants. This work aims at the exploration of underlying physics of steam–water DCC in two dimensions using ANSYS FLUENT 14.5. The volume of fluid method is utilized for performing direct simulation of the phenomenon at the phase interface. In this work, thrust is given on the modeling of the interphase heat transfer using interfacial jump approach instead of proposed empirical correlations which have different applicability limits. User-defined functions in the FLUENT software are used for evaluating the interfacial mass transfer rate, thermal gradient across the phase interface, and interface curvature. This study also emphasizes on the prediction of transient temperature field and interface characteristics under different parametric conditions (e.g., variation of water injection velocity and water temperature). Observation reveals that the present condensation model is capable of capturing the transient temperature history as well as the flow regime transition (stratified to slug flow) induced by the interfacial instability.

Nomenclature

aint	=	Interfacial area density (m−1)
Cp	=	specific heat capacity at constant pressure (J kg−1 K−1)
g	=	acceleration due to gravity (m s−2)
h	=	enthalpy (J kg−1)
	=	mass transfer rate (kg m−3 s−1)
	=	unit normal vector
P	=	pressure (Pa)
Pr	=	Prandtl number
	=	heat flux (W m−2)
Re	=	Reynolds number
Sm	=	energy transfer rate (J m−3 s−1)
T	=	temperature (K)
V	=	velocity (m s−1)
x, y	=	Cartesian co-ordinates
Greek Letters	=
α	=	vapor volume fraction
ρ	=	density (kg m−3)
μ	=	dynamic viscosity (kg m−1 s−1)
λ	=	thermal conductivity (W m−1 K−1)
κ	=	turbulence kinetic energy (m2 s−2)
	=	turbulence dissipation rate (m2 s−3)
Subscripts	=
eff	=	effective
g	=	vapor phase
in	=	injection
int	=	interface
k	=	phase index
l	=	liquid phase
sat	=	saturation
t	=	turbulent
w	=	wall

Nomenclature

aint	=	Interfacial area density (m−1)
Cp	=	specific heat capacity at constant pressure (J kg−1 K−1)
g	=	acceleration due to gravity (m s−2)
h	=	enthalpy (J kg−1)
	=	mass transfer rate (kg m−3 s−1)
	=	unit normal vector
P	=	pressure (Pa)
Pr	=	Prandtl number
	=	heat flux (W m−2)
Re	=	Reynolds number
Sm	=	energy transfer rate (J m−3 s−1)
T	=	temperature (K)
V	=	velocity (m s−1)
x, y	=	Cartesian co-ordinates
Greek Letters	=
α	=	vapor volume fraction
ρ	=	density (kg m−3)
μ	=	dynamic viscosity (kg m−1 s−1)
λ	=	thermal conductivity (W m−1 K−1)
κ	=	turbulence kinetic energy (m2 s−2)
	=	turbulence dissipation rate (m2 s−3)
Subscripts	=
eff	=	effective
g	=	vapor phase
in	=	injection
int	=	interface
k	=	phase index
l	=	liquid phase
sat	=	saturation
t	=	turbulent
w	=	wall

Acknowledgments

The authors would also like to thank Dr. Pallab Sinha Mahapatra, Assistant Professor, Department of Mechanical Engineering, IIT Madras, India for the valuable suggestions to improve the quality of this work.

Additional information

Funding

The first author is grateful to Department of Science and Technology (DST), Government of India for providing fellowship under the INSPIRE program.