Trouble shooting air distribution problems in mechanically ventilated offices often has to be carriedout in limited "after hours" periods. The method of applying a pulse of tracer to the fresh air supplyhas been found to be too time consuming to map the local mean age of air over complex floor plans.In response an automated gas chromatograph has been developed to make air change efficiencymeasurements in real time using the method of homogeneous emission.
Concentrations of indoor air contaminants are normally calculated by assuming that they fullyfollow airflow paths in a room. This assumption is also used to predict the local residence timeof contaminants in a room, which may further be used to characterise the ventilation effectiveness.In this paper, a different methodology has been adopted, in which indoor airborne particles do notalways follow the main airstream induced by the ventilation system. Dispersion of particles ispredicted by a drift-flux model.
The series connected heat exchangers - configured either as an arrangement of gas-gas,gas-liquid or liquid-liquid heat exchangers- are widely used in the process industry andair-conditioning where they can be found in a variety of heat (cool) recovery, in heating andcooling applications.
This paper gives an overview of duct leakage issues in Europe. A literature review indicates alack of ductwork air tightness measurement data in the member states. However, based on afew papers and above all on a field study on 22 duct systems in France, we conclude that theventilation and energy use implications of leaky ducts are large and merit furtherexamination. To this end, we have started the SAVE-DUCT project (1997-1998) aiming atstudying the potential implications of a tight air duct policy at the European level.
Air flow through doors, windows and other large openings constitutes a major factor inbuilding ventilation. However, due to the complexity of the physical processes involved,relevant physical phenomena are not yet fully understood.The paper presents data obtained from five consecutive experiments concerning air flowthrough a large opening (door) connecting two rooms (volumes 28.3 m and 38.1 mrespectively) with different air temperatures.
Checking models of thermal behaviour or ventilation of a room can be performed in specialtest cells. At EMPA a ventilation test chamber with several experimental facilities has beendesigned and built. The inside wall surface temperatures of the chamber can be controlledusing a software model which simulates the thermal behaviour of a real wall. As a test case aheated office room was calculated with TRNSYS and compared with measurements made inthe chamber.As an example of checking ventilation models the validation of a CFD-model of ahorizontally pivoted window is presented.
Perceived barriers restricting the implementation of natural or simple fan assisted ventilationsystems in the design of new office type buildings and in the refurbishment of existing suchbuildings have been identified in seven central and north European countries with moderate orcold climate: United Kingdom, Belgium, The Netherlands, Switzerland, Norway, Sweden andDenmark.The barriers were identified in an in-depth study with structured interviews based onquestionnaires among leading designers and decision makers: architects, consultant engineers,contractors, developers, owners and governme
Existing infiltration and exfiltration calculation methods are mainly based on the stationaryapproach, where long term mean values are used for wind input data. The real wind speed is,however, varying continuously with time. Because the process of the crack flow is non-linear,using mean wind speed values will give erroneous results for the air flows.
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