computational fluid dynamics

The existence of air leakages in a building has been very clearly stated as an important reason for energy loss. The decrease in the efficiency of the mechanical ventilation has also been clarified. The global demand for achieving nearly zero-energy buildings makes the uncontrolled leakage paths even more undesired. Despite the fact that steady state measurements of in- and exfiltration rates offer a simple and easy way of estimating the airtightness level of an eclosure, a supplement to those methods might be imposed.

Air quality in offices depends on the ventilation system ability to remove contaminants from the occupied zone. In a low polluted building air quality mainly depends on the human presence and carbon dioxide is normally used as indicator of human bioeffluents.

Wind is a potential dominant factor regarding the air infiltration through building envelopes. Due to its dynamic characteristics, quite complex aerodynamic phenomena arise around a structure or through cracks and openings. Energy perfomance is influenced by the climate conditions and thus it should be much more researched. Despite the fact that steady state measurements of infiltration rates offer a simple and easy way of estimating an enclosure’s airtightness level, a supplement to those methods might be imposed.

In order to insulate buildings more efficiently, many insulation methods have been proposed and successfully applied to the building envelope, including areas such as walls and windows. However, it is also important to insulate window frames efficiently because they usually contribute the greatest heat loss. The authors propose a new dynamic insulation system for window frames, with an active ventilation function and a heat pump for heat recovery.

The use of CFD technique for predicting the properties of airflow fields and particle movement is effective to carry out parametric study intended for a wide range of particle sizes. In this study, particle dispersions due to turbulent flow and thermophoretic effect were analyzed for a simplified ventilator model. Numerical results that comprise a classification of particle motion, temperature difference and particle diameter were reported.

The air pumping effect of a fire plume, proposed years ago, to give a higher air intake rate through vertical openings in a compartment fire is further investigated in this paper. Equations for the air intake rate through vertical openings found in the literature are reviewed. As most of the reported correlation expressions were derived empirically from experiments, results might be different if the fire geometry, fuel type and ambient conditions are different.

This study presents an optimization method of sensor layout to improve identification accuracy of indoor contaminant sources. The method integrates an index, the performance of sensor layout (PSL), with a two-step screening procedure to determine sensor layouts that have potential to achieve relatively high levels of accuracy in source identification. Using the PSL, the performance of each possible sensor layout can be predicted and evaluated, and therefore the optimization method can be performed without running a source identification model.

The need to protect susceptible patients from cross-infection resulting from airborne pathogens is essential in hospitals, especially when patient immunity is either suppressed due to medical procedures or compromised by ailment. Personalised ventilation (PV) is a method of creating a local zone of high air quality around such patients. However, contemporary PV techniques are based on mechanical ventilation, which adds to the energy burden of healthcare buildings. In single-bed wards, a potential source of infection could be other occupants such as visitors and healthcare workers.

Computational Fluid Dynamics (CFD) is evidently relevant to the study of fires, yet the intermediate chemistry has yet to be factored successfully into combustion models. Consequently, predicted airflow patterns, together with pressure and temperature contours, are mostly used in evaluating the performance of smoke control systems. But even using these assumptions, very few studies exist comparing predicted results from CFD with experimental findings. This leaves research with a paucity of data on how smoke is likely to spread, fill and be controlled in large halls.

This paper reports a critical analysis of the assessment of contaminant removal efficiency. Measurements have been carried out in a ventilated room equipped with a pine wood floor, which emits Volatile Organic Compounds (VOCs), considered as air pollutants in this paper. Thereafter, Computational Fluid Dynamics (CFD) simulations are performed. CFD results are compared to measurements to check their accuracy. Moreover, air quality within the ventilated room is numerically analysed via indices.