Transcript Presentation

The Effect of Plugging Tubes
on the
Gas Mixing in AGR Boilers
Alastair West
1st Year EngD student
Outline
• Background to the Problem
• Overall Objectives of Research
• Use of Code_Saturne
• Future Developments
Background
• 30 years of AGR operation have lead to boiler tubes being
‘plugged’ in order to prevent leakage into the primary circuit
• Adverse effect on the spread of stream temperatures within the
boiler tubes and therefore on the stability at low loads
• Effect will deteriorate with time, threatening the scheduled lifetime
of the AGRs
Overall Objective
• Current boiler code (HEBMIX) is a designspecific lumped-parameter code using
potentially inaccurate mixing data when
plugged tubes are considered
• Provide a sensible computer-based predictive
model of the effect of tube plugging into the
existing boiler code for designs at Hinkley Pt B
and Hunterson B
Boiler Geometry
Experimental Data
• Configuration suggests extremely good CO2 mixing
• Distinct sideways drift of the peak on each successive
temperature profile curve
• Predicted overall swirling motion inside the boiler casing.
Predicted Swirl
Initial Calculations
• Square in-line configurations of different pitch (longitudinal and
transverse pitch are equal) (1.4, 1.5 & 1.6)
• Include heat transfer prediction
• Deduce best performing turbulence model
• Validate with LES data from Afgan and experimental data from
Aiba, 1982
Mesh
Future Extensions
• Coarsen mesh in order to include all 22 tube
rows and unit casing, whilst still capturing the
secondary flow and blank tube effects
• Does this change from initial flow calculations
with periodic boundary conditions?
Long-term Developments
• Implement Analytical or Numerical Wall
Function treatments in order to compute
• Use conjugative heat transfer
• Implement improvements to the current
lumped-parameter boiler code (HEBMIX)
Improvements on an unsteady
eddy viscosity model with stressstrain lag sensitivity
Neil Ashton
1st Year PhD student
Background
•
A eddy viscosity model based on the SST model with an added
transport equation to model the stress-strain lag was developed by Revell
(2006)
• This model will be developed further and implemented with the Phialpha model of Billard (2009) to see if this brings any improvements over
the current SST model which it is based upon.
• Work will be undertaken to understand the benefits of the SST model
against the Phi-α with the aim of making the C_as model of Revell more
robust and suitable for a range of flows
Current Work
I am currently getting to grips with Code Saturne, by running several test
cases including Channel flow at various Reynolds numbers and a
NACA0012 airfoil at high incidence.
Further test cases will be an oscillating channel flow and a
diffuser in the short term. With more complex cases relating the
motorsport section being in the long term.
I haven’t been using the GUI as I wanted to get to grips with the
subroutines, and also because I will need a good knowledge of
these before I can implement any improvements to these models.
NACA0012
Future work
The C_as model of Revell is currently implemented in the 1.1 version of
Saturne and thus my task this summer will be to update this to the
current 1.4 version.
This will be a big task to someone who is relatively new to
Saturne and this is way I am getting to grips with Saturne via test
cases first to gain an further understanding before getting into the
many subroutines which will need updating.
The use of this model in a hybrid RANS/LES scheme is something
which could be investigated in the future depending on how well
the new model performs.
Thank you