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A visual inspection method to evaluate cleanliness of newly installed air ducts

Visual inspection is a subjective method but yet necessary to control duct cleanliness. In order to improve its reliability, a visual scale has been realised and results from a panel of 10 inspectors have been compared to measurements.

The field comparison of three measuring techniques for evaluation of the surface dust level in ventilation ducts

Three measuring techniques have been compared for evaluation of the surface duct level in ventilation ducts : vacuum test, gravimetric tape method, optical tape method. Measurements have been operated in 13 recent buildings in Helsinki using the three methods. The vacuum test gives similar values to the gravimetric tape method when air ducts show no residual oil from their manufacturing (average values 1.1 and 1.2 g/m2). With residual oil, vacuum test gives higher dust levels than gravimetric tape method. The optical tape method is the most easy to use on site.

A control of supply duct outlet air temperature in PEM.

The work presented here is a design and implementation of PID control system to regulate a supply duct outlet air temperature in PEM (Personal Environment Module). Simulation is done first to understand the relationship between a temperature distribution in task space, flow rate and the outlet air temperature of PEM. Then a linear dynamic model of heating process of PEM is obtained P, PD, and PID type control systems, to provide the rapid response without overshoot and saturation, are designed and implemented.

Ventilation effectiveness of large space with swirling airflow formed by the multi-openings square ducts.

If the swirling airflow is formed in the room, the ventilation effectiveness in the room becomes better than by the other method, as the airflow pattern has the fixed direction and the stable airflow path is built up. To make swirl the room air, it is necessary to supply getting larger airflow rate toward outer zone from center. To supply such an airflow distribution simply is used the multi-openings square duct. The reason is that the supply airflow distribution of multi-openings duct has a tendency to increase toward the tip.

Energy efficient ventilation filters.

To ensure good indoor air quality in buildings, filters are installed in the ventilation ducts. These filters cause a pressure drop in the ducts, so that increased power to the ventilation fans is required to maintain the flow of fresh air. To reduce this problem, the Norwegian company, Interfil, developed a new energy efficient filter in 1995. This filter has been carefully tested in recent years. The test results show that, compared to ordinary filters, the new filters could reduce fan power by about 10%, while maintaining indoor air quality.

HVAC duct system design using genetic algorithms.

A genetic algorithm technique is used to design an HVAC air duct system with minimum life-cycle cost. The approach has the capability to incorporate standard (discrete) duct sizes, variable time-of-day operating conditions and variable time-of-day utility rates. An example is used to illustrate these capabilities and results are compared to those obtained using weighted average flow rates and utility rates to show the life-cycle cost savings possible using this genetic algorithm methodology.

Study on contamination control of airborne particle from air conditioning systems in Japanese buildings.

Field studies were carried out on air contamination by dust particles from air conditioning systems in four buildings in Tokyo area. We tried to investigate contamination of airborne particle and surface contamination by sedimentary dust in air duct, and considered a matter in all its aspects that caused indoor air pollution.

1. Time variations of airborne particle concentrations at supply outlet were influenced by the operation of air conditioning system.

Dispersal of spores from fungal-contaminated duct material.

Fungal-contaminated air handling systems have been implicated as a source for the dispersal of spores into the indoor environment, potentially serving as a route of exposure to building occupants. Because quantitative data are lacking, this study was conducted to measure the dispersal of spores from fungal colonies growing on three types of duct material: galvanized metal, rigid fibrous glass ductboard, and fiberglass duct liner.

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