CFD

A quadrature method of moments, based on the population balance approach, was chosen to model nanoparticle coagulation and transport. Such a way has been already validated using experimental results in a homogeneous closed chamber in a steady fluid. In order to model the spatiotemporal evolution of a nano-aerosol, we propose here to couple the population balance equation (PBE) with computational fluid dynamics (CFD) considering a uniform pipe flow. A source term describing coagulation is added in convection-diffusion equations.

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.

In order to ascertain the relationship between opening conditions and indoor airflow characteristics, case studies were conducted by performing CFD analysis using the domain decomposition technique. Reproducibility of the domain decomposition technique was verified through wind tunnel experiments, and the correspondence was confirmed to be satisfactory. The authors confirmed the validity of a method of evaluating cross-ventilation performance which uses wind velocity ratios and ignores regional and meteorological locality.

The Aluminerie Alouette Inc. (AAI) smelter in northern Quebec, Canada recently completed a major plant expansion that includes a new casthouse for the continuous production of low-profile, air-cooled aluminium sows. The radiation and convection heat release of 15 MW to the workplace from the aluminium metal solidification and cooling is significantly higher than that experienced in the traditional water-cooled casting process where the majority of the heat is removed by the cooling water.

In a simple single-zone building with two openings under an opposing wind, a macroscopic theoretical analysis of smoke flow direction and smoke mass flow rate is carried out. Three solutions of smoke flow are identified under the same building geometry, the same heat release rate and the same ambient conditions at the steady state. Two of the solutions are shown to be stable and one is unstable. In the two stable solutions, one is an upward smoke flow with an upper smoke layer and a lower air layer, which may be considered relatively safe in terms of smoke control and human evacuation.

This paper reviews the application of CFD for designing and parametric studies of wind-induced natural ventilation. The approaches employed in such applications of CFD are whole-domain and domain-decoupled CFD modelling. The domain-decoupled technique separately analyses the external airflow fields outside and internal flows inside a building. In the whole-domain approach, the outdoor and indoor airflow is modelled simultaneously and within the same computational domain.

There is a growing desire to reduce peak temperatures within non-domestic buildings by accessing the thermal mass of separating floors. These floors are typically formed of concrete and can store reasonable amounts of heat. Unfortunately, they are usually thermally isolated from the room below by a suspended ceiling. Therefore, some architects try to access the concrete by leaving a perimeter gap in the suspended ceiling in each room to allow airflow across the underside of the separating floor. For visual and acoustic reasons, there is the desire to make this gap as small as possible.

Investigations were carried out into the airflow in a non-unidirectional airflow cleanroom and its affect on the local airborne particle cleanliness. The main influence was the method of air supply. A supply inlet with no diffuser gave a pronounced downward jet flow and low levels of contamination below it, but poorer than average conditions in much of the rest of the room. A 4-way diffuser gave much better air mixing and a more even airborne particle concentration throughout the cleanroom.

Windcatchers are roof mounted devices that use the action of the wind to provide top down natural ventilation to a room. Here, fresh air is channelled into a room while, at the same time, stale air is drawn out. This provides a simple but attractive natural ventilation methodology that is increasing in popularity in U.K. schools. However, an analysis of system performance has largely been limited to laboratory based measurements and the use of CFD to generate predictions.

The prediction of indoor airflow is indispensable in evaluating the thermal sensation of occupants in a cross-ventilated space because enhanced heat loss due to the elevated convective heat transfer in the occupied zone is an essential part of improving thermal comfort. A domain decomposition technique was developed to separate CFD for internal cross-ventilation flow from external flow outside buildings, and to predict indoor airflow with reasonable computational effort and sufficient accuracy.