Airflow network

This paper presents a validation of airflow network (AFN) and computational fluid dynamics (CFD) simulations for a naturally ventilated office building using wind tunnel measurements as the reference for external pressure coefficients and effective airflow rate prediction. The CFD simulation model is also used to study the effect of partially open windows on the effective flow rate. This study also includes a design exercise for a naturally ventilated office building that analyses the differences in predicted average window open area for a typical weather year.

We present a study of natural ventilation design during the early (conceptual) stage of a building's design, based on a field study in a naturally ventilated office in California where we collected data on occupants' window use, local weather conditions, indoor environmental conditions, and air change rates based on tracer-gas decay. We performed uncertainty and sensitivity analyses to determine which design parameters have most impact on the uncertainty associated with ventilation performance predictions.

Mixed-mode ventilation uses intelligent switching between natural and (partly) mechanical ventilation modes to find the best possible balance between indoor air quality, user comfort and energy consumption. It applies demand-control at the level of the operating mode depending on the constraints imposed by the building, its users and its surroundings. Although mixed-mode ventilation is said to have the potential to achieve a comfortable and healthy indoor environment while achieving significant energy savings, it is rarely used in practice.

Pressure coefficients (CP) are fundamental to calculate ventilation rates in buildings by the airflow network models (AFN). This paper deals with the use of CFD simulation to calculate Cp, and the use of those Cp values as input in building energy simulations (BES). The commercial package CFX was used to calculate CP for a 5-stories isolated building, typically found in social housing complexes in Brazil, The standard k-ε turbulence model was adopted.

Despite a lot of Integrated Design Process guidelines and procedures have been developed in the last few years, more specific energy design procedures are needed to push the implementation of passive design techniques.

When it comes to natural ventilation performance for large space cooling during summer time or intermediate seasons, double skin facade(DSF) integrated with cross ventilation(CV) exhibits more energy efficiency than single-side ventilated DSF. In this case, ventilation performance is remarkably affected by climatic conditions. Therefore, it is important to analyze micro climatic conditions before applying this passive technique.

The numerical investigation of airflow and chemical transport characteristics for a general class of buildings involves identifying values for model parameters, such as effective leakage areas and temperatures, for which a fair amount of uncertainty exists. A Monte Carlo simulation, with parameter values drawn from likely distributions using Latin Hypercube sampling, helps to account for these uncertainties by generating a corresponding distribution of simulated results.