The Use of Computational Fluid Dynamics in Natural Ventilation Strategies

David Banks, Cermak Peterka Petersen Inc.
Robert V. Schroeder, P.E., Glumac International

Objectives:

This presentation illustrates the manner in which Computational Fluid Dynamics (CFD) can be used to model internal flows for natural ventilation in research buildings. The presentation will describe both the strengths and limitations of CFD for this type of analysis.

The objectives of our presentation will illustrate the process of how computational fluid dynamics fine tunes the building into a model of energy efficiency and promote natural ventilation strategies. The key is to provide the CFD modeling very early in the project, when the ability to change the architectural features is easy to accomplish. This is true because CFD modeling typically identifies subtle nuances that will allow natural ventilation to occur, provided the building architecture is willing. This will always include tradeoffs, and those can be easily made in the early stages of the design. This process is highlighted in our presentation.

The next objective is to get the end user occupant to buy in on all of these considerations. This will allow more of the building to open up to the outside and have more occupant control. Once buyoff is accomplished, systems can be downsized and reduce operating hours. The energy implications are obvious.

Findings:

A CFD analysis allows an estimate of the energy savings due to natural ventilation to be made. By performing a CFD analysis as a design tool at an early stage of the building formation, the locations of natural ventilation inlets and exhausts can be selected to take advantage of external wind pressures patterns on the building.

We would also like to discuss what worked well in terms of final design features and what did not due to other constraints. This produces tradeoffs between building architectural, structural, electrical and mechanical components that led to a best fit to satisfy everyones concerns. In some cases natural ventilation strategies had to be modified and rerun through the CFD model to determine performance characteristics. We would also like to discuss the implications of commissioning on the project as it relates to these intricate systems to ensure that ventilation strategies are employed.

Labs21 Connection:

The Labs21 approach is akin to the LEED™ process for laboratory buildings and looks at whole building analysis. Towards that end, our experience is that mechanical and electrical systems can be simpler and more straight forward assuming that the architectural building is fully integrated and takes advantage of natural architectural elements and outdoor environmental considerations. We would like to discuss the aspects of the energy and CFD models that relate to fine tuning of the building relative to these subsystems. As always, a green building promotes energy conservation through all of its components and this will be illustrated on our project. The issue of productivity is one that is brought up a lot in concert with sustainable buildings and feel that natural ventilation strategies through CFD modeling will truly promote a working environment that is more desirable.

Biographies:

David Banks completed his Ph.D. in Wind Engineering at Colorado State University in 2000. His dissertation focused on the fluid dynamics of roof corner vortices. It produced four refereed publications was awarded the Robert H. Scanlan Outstanding Ph.D Award at the 2001 Americas conference on Wind engineering. He has both masters and bachelors degrees in Aerospace Engineering from the University of Toronto. He worked for several years as computer code review specialist at Canada's nuclear regulatory agency. At CPP, he has recently worked on a range of internal flow CFD simulations, including animal holding rooms, atrium fires, and an external flow pollutant dispersion validation study.

Robert V. Schroeder, P.E., is an Associate Principal at Glumac International. He has extensive experience in all phases of the design, including supervision of multi-disciplinary teams; preparation of all mechanical construction drawings and specifications; construction observation; and cost estimating. His expertise includes interfacing with clients, tracking project schedules and budgets, and supervising engineering and CADD personnel. Mr. Schroeder's project experience includes complete mechanical system design for health care (hospitals and medical office buildings), higher education (libraries, laboratories, and campus buildings), commercial and institutional buildings; industrial and municipal facilities, high tech (laboratories and clean rooms), correctional facilities, museums, and cultural centers.