PQU Phase 2 CHP Plant Flow balance: Analysis for PB do Brasil
The computational problem was formulated from the data provided (e.g. technical
drawings and steam flow conditions). The HRSG pipeline connection (320 t/h of flow),
named T1, was set at 1,100 mm from from the T2 connection. I have visualized the
absolute pressure and the flow velocity. I have zoomed on to the three T connections
(named T1, T2, T3).
Distances from the end points to the Tjunctions are 5 diameters for Tjunctions
connecting INLETS, and 10 diameters for Tjunctions connecting OUTLETS. (Details are
shown below.) This choise was due to the assumption that the flow is clean in the
inlet pipeline sections and “dirty” in the outlet sections. The results prove so.
The pressure is almost constant (equal to 114 bars), while there are enornous changes
on the velocity field. This is of course due to the outflow conditions (set as specified.)
Problem Approach
 CFD solution (NavierStokes Equations)
 Twodimensional blockstructured grid
 Fully turbulent flow with keps model
114 bar System, Graphic Analysis INLET FLOWS 410 t/h, 180 t/h
Problem Definition
 Inlet temperature T = 510 Celsius
 Inlet pressure p = 114.0 bar
 Inlet density = 34.48 kg/m³ (linear interpolation from steam tables at 500 C)
 Flow dynamic viscosity 3. 10^{5} N m/s
 Outlet: as specified Mr Barry O’Connor (private conversation, Dec 12, 2001)
The results are presented in a similar way as for the earlier cases (as discussed below).
It is evident the increased steam velocity on the section leading to T1 (due to 410 t/h) of steam. The are only minor changes in pressure, as expected.
114 bar System, Graphic Analysis # Junction T1T2 = 1,100 mm
Problem Definition
 Inlet temperature T = 510 Celsius
 Inlet pressure p = 114.0 bar
 Inlet density = 34.48 kg/m³ (linear interpolation from steam tables at 500 C)
 Flow dynamic viscosity 3. 10^{5} N m/s
 Outlet: as specified in Flow Balance Drawing (Rev.1 /21.11.01)
114 bar System, Graphic Analysis
# Juction T1T2 = 1,500 mm
Problem Definition
 Inlet temperature T = 510 Celsius
 Inlet pressure p = 114.0 bar
 Inlet density = 34.48 kg/m³ (linear interpolation from steam tables at 500 C)
 Flow dynamic viscosity 3. 10^{5} N m/s
 Outlet: as specified in Flow Balance Drawing (Rev.1 /21.11.01)
Discussion of Results
The first calculation was performed with a distance T1T2 of 1,500 mm. This turned out
to be a different configuration than the actual installation, therefore the model was
changed to take into accout the distance T1T2 = 1,100 mm. All other parameters are the
same.
The analysis is twodimensional, e.g. the flow occurs in a plane. In the actual
pipeline installation T1 and T2 come at 45 degs with respect to the horizontal. This
effect is considered negligible, although the threedimensional effect of the
junction could be more important, especially if T1 and T2 are very close. A
quantitative analysis will not be possible within the framework of this scope of
work, but it is safe to assume that T1 and T2 should be placed as far as possible
from each other, to avoid choking, unsteady loads, and vibrations.
The pressures change very little in the model, as they are around 114 bars everywhere
(please check the scale in all the graphics). Therefore, no appreciable gradients have
been found.
The case of the flow velocity is quite different. Both analyses show that there are
major speed variations.
Comparison of Velocities at T1
T1T2 = 1,100 mm: The flow is chocked in the direction of OUTFLOW to the PQU 8 MW
turbine (this does not appear in the case T1T2 = 1,500 mm).
Comparison of Velocities at T2
T1T2 = 1,100 mm: The flow is chocked in the direction of OUTFLOW to the PHASE I 17
MW turbine (this does not appear in the case T1T2 = 1,500 mm).
Comparison of Velocities at T3
No major differences were detected. The 50 t/h flow to the right is moderately slow.
It is believed that the installation with T1T2 = 1,500 mm is better than the T1T2 =
1,100 mm.
53 bar System, Graphic Analysis
 Inlet temperature T = 400 Celsius
 Inlet pressure p = 53.0 bar
 Inlet density = 18.30 kg/m³
 Inlet velocity = 64.0 m/s
 Flow dynamic viscosity 3. 10^{5} N m/s
 Outlet: as specified in Flow Balance Drawing (Rev.1 /21.11.01)
Velocity Field
Discussion of Results
I have shown only the results, as the pressure has only minimal changes (as in the
case of 114 pressure). There are considerable changes in the velocity field all
the way to the end of the section modelled (20 diameter lengths downstream
the bend. The maximum absolute speed is of the order of 80 m/s. The vortex
right at the exit of the bend indicates that the flow is choked. This is due to
the high mass flow of this case (350 t/h).
Filed on December 4, 2001
Document Class: CLASSIFIED
Document Number: AFAEROUMIST0112

Dr. A. Filippone
UMIST
Dept of Mechanical and Aerospace Engineering
ThermoFluids Division, P.O. Box 88
Manchester M60 1QD
United Kingdom
phone (+44) 161 – 200 3702
telefax (+44) 161 – 200 3723
Email:

