Coupling Computational Fluid Dynamics
and Finite Element Analysis to Optimize
Heat Transfer in Buildings
Vincent Y. Blouin, PhD
Assistant Professor
School of Architecture
School of Materials
Science and Engineering
Outline
• Research goals
• Thermal behavior of buildings
• Method
– Finite Element Analysis (FEA)
– Computational Fluid Dynamics (CFD)
– Coupling FEA and CFD
• Numerical difficulties
• Results
• Conclusion
Research Goals
• Develop numerical simulation of thermal
behavior of buildings by combining CFD and
FEA in an iterative transient model.
• Use model in architectural building design and
optimization to maximize building performance
and minimize energy consumption by integrating
advanced materials (e.g. Phase Change
Materials).
Rationale for the Research
• Emergence of new advanced materials in
architectural design justifies the need for
advanced design methodologies.
• Phase Change Materials (PCMs) have the
potential to reduce energy costs by up to
40% if properly designed. Design rules
based on numerical simulation must be
developed.
Thermal Behavior of Buildings
• Excessive heat gains/losses in buildings are due to:
–
–
–
–
solar radiation
thermal radiation
indoor and outdoor natural and forced convection
heat generation from lighting, appliances, electronics and users
• To mitigate these effects and maintain a comfortable
temperature large amounts of energy are required.
• These effects are time-dependent and control the daily
and yearly thermal balance and fluctuations.
Method
• The transient heat transfer problem of
the building is solved by Finite
Element Analysis (FEA) using
ABAQUS.
• The steady-state fluid flow problem of
indoor and outdoor fluids is solved by
Computational Fluid Dynamics (CFD)
using FLUENT.
• These two interrelated problems are
coupled in an automated iterative
procedure using MATLAB.
Method
CFD
Steady state fluid flow analysis
Input: Wall temperatures
Output: Heat fluxes
FEA
Transient thermal analysis
Input: Heat fluxes
Output: Wall temperatures
• The heat fluxes due to convection are computed by CFD
based on the wall temperatures, which are computed by
FEA based on the heat fluxes.
Method
Steadystate
CFD
Steadystate
CFD
Steadystate
CFD
0
1
2
Dt
Steadystate
CFD
…
…
Transient FEA
24
…
Time (hours)
• The transient heat transfer analysis is controlled by the FEA.
• The time duration is discretized into time increments Dt.
• A steady state CFD analysis is performed at each increment.
CFD Results
• Air flow by natural ventilation through open windows
CFD Results
• Outdoor air velocity field due to a 3-mph transversal wind
(from left to right)
CFD Results
• Indoor surface heat fluxes due to forced and natural
convection
FEA Results
• Temperature distribution through walls
(exterior façade and roof are heated in part by solar radiation)
FEA Results
• Outdoor air velocity field due to a 3-mph transversal wind
(from left to right)
4/13/2015
Vincent Blouin, vblouin@clemson.edu
14
Results
• Temperature fluctuations through building envelope during
a 4-day period
Results
• Comparison of indoor wall temperatures during a 4-day
period without and with Phase Change Materials (PCM’s)
No PCM’s
DT= 5.0oC
With PCM’s
DT= 3.5oC
Latent heat = 10 KJ/kg
Results
• Comparison of indoor wall temperatures during a 4-day
period for two amounts of Phase Change Materials (PCM’s)
Latent heat = 10 KJ/kg
DT= 3.5oC
Latent heat = 20 KJ/kg
DT= 2.5oC
Computational Issues
• Design and optimization requires hundreds of
simulations.
• Each simulation is an incremental FEA process
that may require hundreds of CFD analyses.
• Both FEA and CFD are computationally intense.
To achieve the desired accuracy, both models
require millions of degrees of freedom.
Conclusion
• Method is computationally challenging
• However, it provides versatility and freedom in
terms of geometry and material properties
• Provides a way to simulate thermal behavior of
buildings for design and optimization
Future Work
• Validate method with established methods (e.g.
enthalpy method)
• Compare with Fluent’s conjugate heat transfer
method and other multi-physics software
• Study scalability of the method
Thank you!