ducts

Samples of surface dust were collected from ducts before and after an HV AC system cleaning project in an office complex in Canada. Dust levels were quantified gravimetrically and concentrations of viable fungi were determined (1) using a standard dilution plating method from vacuum-collected surface dust samples; and (2) by the collection of surface samples on commercially available agar contact slides.

A large number of modern European buildings are equipped with ducted air distribution systems. Because they represent a key parameter for achieving a good indoor climate, increased attention has been given to their performance during the past fifty years. One aspect that is particularly developed in this handbook concerns the airtightness of the ductwork, which has been identified as a major source of inadequate functioning and energy wastage of HVAC systems. The investigations were carried out within the framework of the DUCT project (1997-1998).

Particle deposition from turbulent duct flow is modelled and related to particle penetration of a ventilation system for a commercial office building. Three published turbulent deposition models capable of accommodating surface roughness are compared to experimental data and used to determine the penetration of 0.1 - 10 (m spherical particles through a sample duct run. Depending on the model employed, penetration fractions varied from 0.40-0.94 for 0.1 (m particles and 0.28-0.73 for 10 (m particles.

An efficient numerical method for solving the Reynolds-Averaged Navier-Stokes (RANS)equations with turbulence models for complex geometry and high Reynolds number flows isused to perform a highly-resolved computation of the turbulent flow in a strongly curved partof a ventilation duct.The three-dimensional incompressible RANS equations and the isotropic k-w two-equationnear-wall turbulence closure are written in generalized curvilinear coordinates in the strongconservation form.