Combined Airflow and Energy Simulation Program for Building Mechanical System Design
Open Access
- Author:
- Novoselac, Atila
- Graduate Program:
- Architectural Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- November 23, 2004
- Committee Members:
- Jelena Srebric, Committee Chair/Co-Chair
Stanley Allan Mumma, Committee Member
William P Bahnfleth, Committee Member
John Harlan Mahaffy, Committee Member - Keywords:
- thermal comfort
IAQ
building analysis
CFD
energy simulation
convection corelation - Abstract:
- Energy and airflow programs are the main tools for designing energy efficient and healthy buildings. Therefore, the goal of this thesis is to develop new models and improve existing models for simulating energy and air flows in buildings. Indoor airflow simulation programs calculate most of the parameters needed to evaluate thermal comfort and indoor air quality. However, it is necessary that airflow simulation programs have correct boundary conditions which can be provided by energy simulation (ES) programs. In order to develop simulation tools for precise evaluations of thermal comfort and indoor air quality in buildings, the existing Computation Fluid Dynamics (CFD) airflow program is improved by adding new models for the calculation of thermal boundary conditions. Subsequently, this program is coupled with the newly-developed ES program. This thesis considers different methods for coupling ES and CFD programs with particular attention given to boundary conditions on enclosure surfaces which connect the modeling domains of these two programs. Three different coupling approaches were investigated with special consideration given to accuracy and computation time. The results show that the Integrated Coupling Method provides the optimum compromise between accuracy and computation time. In order to improve the accuracy of the calculations of thermal boundary conditions on building internal surfaces, experiment-based convection correlations are implemented in the CFD program. In the process, new convection correlations are developed based on measurements conducted in a state-of-the-art experimental facility. Correlations for characteristic surfaces in rooms with: cooled ceiling panels, displacement ventilation, or high aspiration diffusers are developed. Furthermore, additional experiments are performed to collect data so as to validate new models for calculating thermal boundary conditions. A comparison of numerical and experimental results shows that the new models for thermal boundary conditions calculation, implemented in CFD, perform substantially better than wall functions. A certain level of grid dependency of heat flux calculation with new models still exists. However it is much smaller than with wall functions. Finally, this thesis provides examples, which demonstrate that the coupled ES and CFD program is an effective tool for the evaluation of energy consumption, thermal comfort, and air quality in buildings.