[Charon]

Hi,

my modell consists out of two concentric copper cylinders with water beteen them. The cylinders are heated by an constant energy source. the flow inside the fluid domain is driven by the buoyant effect(heat flux from the cylinders) and an external caused mass flow(also caused by buoyant, which is not part of the modell).

I'm using Ansys Workbench 14 with CFX 5

My question is, if my setup of the boundaries is realistic?

The inlet conditions are:
BOUNDARY: Oil_Inlet
Boundary Type = INLET
Location = Part1_Oil_Inlet
BOUNDARY CONDITIONS:
FLOW DIRECTION:
Option = Zero Gradient
END
FLOW REGIME:
Option = Subsonic
END
HEAT TRANSFER:
Option = Static Temperature
Static Temperature = TempIn
END
MASS AND MOMENTUM:
Option = Static Pressure
Relative Pressure = 0 [Pa]
END
TURBULENCE:
Option = Medium Intensity and Eddy Viscosity Ratio
END
END
BOUNDARY SOURCE:
SOURCES:
EQUATION SOURCE: continuity
Flux = MassflowEintritt
Option = Fluid Mass Flux
VARIABLE: T
Option = Value
Value = TempIn
END
VARIABLE: ke
Option = Value
Value = 0 [m^2 s^-2]
END
VARIABLE: tef
Option = Value
Value = 0 [s^-1]
END
VARIABLE: vel
Option = Cartesian Vector Components
xValue = 0 [m s^-1]
yValue = 0 [m s^-1]
zValue = VEintritt
END

The outlet conditions are:
BOUNDARY: Oil_Outlet
Boundary Type = OUTLET
Location = Part1_Oil_Outlet
BOUNDARY CONDITIONS:
FLOW REGIME:
Option = Subsonic
END
MASS AND MOMENTUM:
Option = Average Static Pressure
Pressure Profile Blend = 0.05
Relative Pressure = 0 [Pa]
END
PRESSURE AVERAGING:
Option = Average Over Whole Outlet
END
END
END

The reason why i have chosen this setup is:

1.Since there is the possibility, that the flow driven by the buoyant effect could be bigger than the one driven by the external caused massflow, I modelled the inlet as if it is an opening(inlet to prevent a backflow).

2.In order to prevent an flow driven by a pressure differnce between inlet and outlet(outlet to prevent backflow), I set the pressure at both boundarys to 0(relative).

3.The external driven massflow i modelled as an boundary source at the inlet.


Thank for your help.

Greetings
Philipp