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
FEATransient thermal analysisInput: Heat fluxesOutput: Wall temperatures
CFDSteady state fluid flow analysisInput: Wall temperaturesOutput: Heat fluxes
• 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
• 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.
Transient FEA Time (hours)
0 1 2 24 …… …
Steady-state CFD
Steady-state CFD
Steady-state CFD
Steady-state CFD
t
FEA Results
• Temperature distribution through walls (exterior façade and roof are heated in part by solar radiation)
04/20/23 Vincent Blouin, [email protected] 14
Results
• Comparison of indoor wall temperatures during a 4-day period without and with Phase Change Materials (PCM’s)
No PCM’sT= 5.0oC
With PCM’sT= 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/kgT= 3.5oC
Latent heat = 20 KJ/kgT= 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
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