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Comparing zonal and CFD model predictions of isothermal indoor airflows to experimental data

Mora, L., Gadgil, A. J. and Wurtz, E.
2002
Indoor Air, 13(2)

Mora, L., Gadgil, A. J. and Wurtz, E., (2002), "Comparing zonal and CFD model predictions of isothermal indoor airflows to experimental data", Indoor Air, 13(2).
Abstract:
It is inappropriate to use the assumption of instantaneously well-mixed zones to model airflows and pollutant transport in large indoor spaces. We investigate two approaches for describing the details of airflows in large indoor spaces, for accuracy and suitability for integration with multi-zone infiltration models. One approach, called the zonal method, was developed over the last 15 years to provide an improvement over the well-mixed assumption. The second approach is the use of a computational fluid dynamics simulation using a coarse grid model of the large indoor space.

We compare velocity predictions from different formulations of zonal methods and coarse-grid k-[epsiv] computational fluid dynamics (CFD) models, to measurements, in a 2D mechanically ventilated isothermal room. Our results suggest that, when airflow details are required, coarse-grid CFD is a better-suited method to predict airflows in large indoor spaces coupled with complex multi-zone buildings, than are the zonal methods. Based on the comparison of pressure predictions from different models, we offer guidance regarding the coupling of a model of detailed airflow in large spaces to algebraic multi-zone infiltration models.

Practical Impliactions

In several applications it is desirable to model airflows and pollutant flows in complex buildings that contain large indoor spaces such as atriums or large conference halls. For developing such an integrated model, one needs to couple one of the common methods for modeling air and pollutant flows in large complex buildings (e.g., COMIS or CONTAM) with an appropriate model of the large indoor space. This work shows that airflow (and therefore air borne pollutant-flow) predictions in large spaces are substantially more accurate when obtained from a coarse-grid CFD model than from various versions of zonal models. The demand for computer resources remains modest with coarse-grid CFD. This work also discusses the practical problems related to developing such model integration by coupling pressures and airflows between a model of the large indoor space and the building airflow network model.
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Author Information and Other Publications Notes
Mora, L.
  1. An integrated zonal model to predict transient indoor humidity distribution
  2. Comparing zonal and CFD model predictions of indoor airflows under mixed convection conditions to experimental data  
Gadgil, A. J.
  1. Comparing zonal and CFD model predictions of indoor airflows under mixed convection conditions to experimental data
  2. Infiltration heat recovery in building walls: computational fluid dynamics investigations results  
Wurtz, E.
  1. An integrated zonal model for predicting transient VOC distribution in a ventilated room
  2. An integrated zonal model to predict transient indoor humidity distribution
  3. Comparing zonal and CFD model predictions of indoor airflows under mixed convection conditions to experimental data
  4. Effects of coupled heat and moisture transfers through walls upon indoor environment predictions  


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