Final Project Presentation:Analysis of Tube Configuration in a Tube

Bundle in Horizontal, Two-Pass Condensers

Engineering ProjectMaster of Engineering in Mechanical Engineering

Jennifer Tansey12/15/11

Introduction / BackgroundA common type of condenser used in steam plants is a

horizontal, two-pass condenserSteam 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” second-pass

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

Case 4 Case 5 Case 6

Performing the AnalysisA heat and mass transfer algorithm was created to

determine the outlet temperature of the circulating water for the six casesSet and/or calculated all geometric, material and

thermodynamic propertiesCreated a velocity profile for the tube bundle, thus

allowing a velocity to be calculated for each row of tubesEvaluated 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-ProcessingCompiled the converged results for the heat flux, interface

temperature and outer wall temperature for all six casesCalculated 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-ProcessingPerformed an energy balance to ensure that

the iterative algorithm produced accurate resultsTook 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 ModelingCreated 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

CondenserHeight(m)

Velocity(m/s)

Condenser Width (m)

CondenserHeight(m)

Velocity(m/s)

Example of FLOW3D Temperature Contours

Tem

pera

ture

(K

)

Cond

ense

r Hei

ght (

m)

Condenser Width (m)

ConclusionsMehrabian-based velocity profile increases through the tube

bundleFLOW3D-based velocity profile decreases through the tube bundleThe cases that exhibit the most heat transfer to the circulating

water in the first-pass are those that experience the highest steam velocityCases 2 and 4 for a Mehrabian-based velocityCases 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 WorkThe FLOW3D simulations could be refined to

more accurately compare the results obtainedThe 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