duct

Although a significant amount of work has been done to elucidate the conditions under which fungi will grow on the surfaces of materials, little information is available that quantitatively relates surface concentrations to airborne concentration and, ultimately, exposure. This paper discusses the impact of relative humidity (RJI), air velocity, and surface growth on the emission rates of fungal spores from the surface of contaminated material.

Canada's Space Centre in St Hubert, Quebec, is a new 27,870 m2 complex which was awarded first place in the ASHRAE Technology Awards (1996) for new commercial buildings. A dual duct ventilation system was installed to provide a comfortable and pleasant research environment. Dual duct systems, which are the heart of the mechanical concept, provide high indoor-air quality, along with design flexibility, energy efficiency and low capital costs.

Constant injection of tracer gas was used to determine the airtightness of a straight length of300 X 300 mm square duct in a laboratory setting. Holes are performed in the ductwork which is connected to a fan with variable speed control to simulate leakages. The holes can be sealed with rubber bungs to simulate an airtight ductwork. 'Stationary' and 'mobile' methods have been developed. The stationary method is suitable for conditions where the locations of the leaks in the ductwork is known.

Particle loss augmentation in turbulent flow was studied experimentally. Experiments were performed in a I SO mm square ventilation duct. Small tracer particles of size ranging from 0.7-7.l μ.m were used to study deposition enhancement with streamwise-periodic disturbances mounted on one of the principal walls, under turbulent flow. A new and highly sensitive analytical technique was adopted to determine the spatial mass flux along the ribbed duct. On some surfaces, particle deposition enhancement as much as seven times higher than on .smooth surfaces was observed.

This paper presents a comparison of predictions from a duct efficiency model developed by the authors with measured real-time heating n, system efficiency measurements from six site-built residential homes with natural gas furnaces in the Puget Sound region. The model takes into account the interaction between supply and return side losses, the interaction between conduction and air leakage losses, the interaction rs between unbalanced leakage and natural infiltration, and the recovery of heat through the building envelope from ducts in various locations 1) within the home.

When a fume cupboard is placed in a room with a ventilation duct, the air movement inside and around the fume cupboard is fully three-dimensional turbulent flow. However, in order to understand the fluid flow away from the fume cupboard a much simpler model can be used. This leads to a steady 20 model, with the computational domain including only the sash of the fume cupboard, the room and the entrance into the ventilation duct. In this paper we have used both the k-E turbulence model and the wall function technique to calculate the steady 20 turbulent fluid flow.