Transcript Final Project Presentation 12.14.11.pptx

Jennifer Tansey
12/15/11
Introduction / Background
 A common type of condenser used in steam plants is a horizontal, two-
pass condenser
 Steam enters the condenser through an inlet at the top of the
condenser and passes downward over a horizontal tube bundle
 The tube bundle is made up of individual tubes through which a
cooling medium circulates to condense the steam
 Typically the tubes in the top half of the tube bundle are the “cold”
first-pass and the tubes in the bottom half are the “warmer” secondpass
Problem Description
 The objective of this project is to analyze the tube configuration in a bundle to
determine the best arrangement of tubes for the maximum amount of heat
transferred to the circulating water
 The six configurations shown are analyzed
 The dark blue denotes the first-pass tubes and the light blue denotes the
second-pass tubes
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Case 1
Case 2
Case 3
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Case 4
Case 5
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Case 6
Performing the Analysis
 A heat and mass transfer algorithm was created to
determine the outlet temperature of the circulating water
for the six cases
 Set and/or calculated all geometric, material and
thermodynamic properties
 Created a velocity profile for the tube bundle, thus allowing a
velocity to be calculated for each row of tubes
 Evaluated all six cases for the same operating conditions and
initial parameters, iterating for each pass in each case until
values for the heat flux, interface temperature and outer wall
temperature converged
 Solved for the outlet circulating water temperature after the
first and second-passes for each case
Post-Processing
 Compiled the converged results for the heat flux, interface
temperature and outer wall temperature for all six cases
 Calculated and plotted the temperature distribution over the length of
the tube bundle for both the first and second-passes using an averaged
circulating water temperatures
 Compared the circulating water temperatures for:
 All first-pass tubes
 Average outlet temperature
 Average temperature along the tubes
 All second-pass tubes
 Average outlet temperature
 Average temperature along the tubes
Post-Processing
 Performed an energy balance to ensure that the
iterative algorithm produced accurate results
 Took into account the change in energy in the system
due to:




Net loss in energy in the mixture
Net gain in energy in the circulating water
Net gain in energy in the condensate formed
Net gain in energy in the tube walls
 Showed less than 3% error, which can be attributed to
the assumptions and simplifications made in the
analysis
FLOW3D Modeling
 Created input files for all six cases in FLOW3D to simulate the
velocity contours and steam temperature contours
 Used the velocity profile from FLOW3D in Excel to repeat the
algorithm with the new velocity profile
 Analyzed and compared the results from the velocity profile
created in the algorithm and the velocity profile obtained from
FLOW3D
Example of FLOW3D Velocity Contours
Condenser Height (m)
Co
nd
en
ser
He
igh
t
(m
)
Velocity (m/s)
Ve
loc
ity
(m
/s)
Condenser Width (m)
Temperature (K)
Condenser Height (m)
Example of FLOW3D Temperature Contours
Condenser Width (m)
Conclusions
 Mehrabian-based velocity profile increases through the tube bundle
 FLOW3D-based velocity profile decreases through the tube bundle
 The cases that exhibit the most heat transfer to the circulating water in
the first-pass are those that experience the highest steam velocity
 Cases 2 and 4 for a Mehrabian-based velocity
 Cases 1 and 3 for a FLOW3D-based velocity
 The circulating water temperatures tend to converge at the outlet of the
second-pass tubes
 The velocity profile is independent of the heat transfer due to the tube
configuration within the bundle
 The magnitude of the velocity is proportional to the amount of heat
transferred
Future Work
 The FLOW3D simulations could be refined to more
accurately compare the results obtained
 The FLOW3D grid that was generated was relatively
coarse and the flow was assumed laminar in order to
expedite simulating all six cases
 A higher grid resolution and assuming a turbulent steam
mixture flow through the bundles would each increase
the predicted maximum velocity through the tubes