Simulation of condensation in a heat exchanger

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Simulation of condensation in a heat exchanger
Group Seminar, Division of heat transfer,
LTH December 6th, 2005

• Charlotte Wilhelmsson
• Division of Heat Transfer
• Lund Institute of Technology

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Outline

• Project description
• Background
• Methods
• Equations
• Future

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Project Description

• Project Title
• Simulation of condensation in a heat exchanger
• Background
• It is interesting to conduct some numerical work
  to gain some insight for this process, although
  may not fully predict it.
• Project is mainly sponsored by STEM, but in
  cooperation with Alfa Laval.

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Plate heat exchanger
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Introduction

• The application of PHEs in process industries
  have been significantly enlarged, due to
• Compactness
• Effectiveness
• Cost competitiveness
• Traditional PHE are plate-and-frame heat
  exchanger
• Temperature limit 160 ºC
• Pressure limit 25 bar

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Condensation

• Involves a phase change
• Saturated vapour such a steam comes in
  contact with a solid whose surface temperature is
  below the saturation temperature.
• Normally when vapour condensates on a surface, a
  film condensate is formed on the surface and
  flows over the surface by the action of gravity.

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Methods

• Possible methods
• Pure CFD
• Simplified numerical model
• Analytical solution

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Original equationsCondensate film
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Original equationsVapour flow
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New coordinates

• Liquid phase
• Vapour phase

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Liquid layer
1.
2.
3.
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Vapour layer
1.
2.
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Boundary conditions

• TV TS
• At the wall
• UL0
• VL0
• TLTW
• At the liquid vapour interface
• UL UV
• ?LVL ?VUV

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What I have been doning since August

• Start to use the CALC-code for my project
• Teaching the course Thermodynamics and Fluid
  dynamics
• Styding the course Convective boiling and
  condensation

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The CALC-code

• Finite volume computer code
• For prediction of mass, heat and momentum
  transfer
• Utilizes a general non-orthogonal boundary fitted
  coordinate system
• Steady/unsteady, three-dimensional,
  turbulent/laminar recirkulating flows

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My case

• Change from horizontal to vertical
• Implement data for water, hydrogen and air
• Implement two-phase flow and phase-change

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U-velocity
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Temperature
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Future work

• Implement condensation in CALC-code

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• Thank you very much