PR1997

The results presented here supply values for the room ventilation efficiency of a number of configurations covering as many as possible of the ventilation systems encountered in actual practice. The study is based on experimental results and numerical simulation. Using a few configurations experimented-on, simulations were performed using CFD code, which in particular allowed the reliability of calculations to be checked. The simulation tool was then used in such a way as to arrive at results that could be applied in practice.

The purpose of this research is to give an overall prospect of the performance of 4 kinds of ventilation systems for dwellings using numerical simulation under various conditions. The total number of combinations of various parameters for the calculation is 174. Calculations for pollutant concentration, humidity and condensation, interior pressure and airflow rate, heat energy by ventilation, etc. are performed hourly through the heating season.

This paper presents an analysis of different possibilities of representing mass transfers in zonal models. In this aim, formulations derived from the Navier-Stokes equations or from Euler's theorem are obtained. The models which result from them and empirical models are compared so that to define the best compromise between simplicity, accuracy and easy convergence.

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