AIVC - Air Infiltration and Ventilation Centre

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mathematical modelling

Influence of air infiltration on the energy consumption in the large industrial halls.

Computer programs INFILS and ACFES2/R have been developed for the analysis of industrial buildings' heating loads and energy consumption relating to air infiltration. The heat demand computation results for typical hall structures are presented. It is shown that on windy days with low outside temperatures, total heat losses rose to 180% of basic heat losses. The necessity of developing proper methods for designing, building and testing elements of industrial buildings is emphasized.

The energy saving effect of double frame windows.

The interaction of air leakage and transmission heat through a double frame window makes the overall heat loss less than the sum of them acting separately. Theoretical calculation shows that in the case of infiltration, a double frame window may recover 21% to 32% of air leakage heat loss, and exfiltrated air through a double frame window not only loses no energy but, on the contrary, reduces the energy consumption of heat transmission, covering 23% to 36% of the enthalpy drop of exfiltrated air before and after leakage. Experimental data and field test agreed well with these results.

The importance of attic ventilation.

Attic ventilation is compared with other means of ceiling heat flux reduction in low cost housing. A simple steady state mathematical model has been run with climatic data for a summer day of Porto Alegre, Brazil. The increase inceiling thermal resistance has proved to be the best improvement, but it is expensive. The greatest proportion in ceiling heat flux reduction is in the natural ventilation range and forced ventilation adds little to it. As natural ventilation does not imply extra cost, it is very important in low cost housing and should be optimised.

Multizone infiltration studies at Lawrence Berkeley Laboratory.

Multizone infiltration requires extensive and complex information about the flow characteristics and pressure distribution inside the building, and thus has been too difficult to develop and to validate. By relying on lumped parameters for the description of air flow distribution in a building, a simplified model is produced. This paper describes the parameters and considerations involved in the development of the multizone infiltration model.

The prediction of air infiltration.

Describes a reasonably accurate method for estimating air infiltration for engineers or energy auditors who are not specially trained in infiltration research. The method requires two steps: field measurement of the building properties, and calculation of the infiltration from weather data and themeasured properties. Fan pressurization techniques are described and how to use them to measure the air tightness of the building envelope, and the procedures required to make infiltration predictions with the Lawrence Berkeley Laboratory infiltration model.

Methods for estimating air change rates and sizing mechanical ventilation systems for houses.

This paper presents a simple method for estimating the total air change rate of a house with or without mechanical ventilation. The proposed method can be used to assess the effect of a mechanical ventilation system on total air change rates. It can also be included in existing simple computer programs forestimating heating requirements for houses. A calculation procedure is also presented for sizing mechanical ventilation systems for houses. This procedure can be used to estimate the forced ventilation rate required to achieve the desired total air change rate.

Influence of open windows on the interzone air movement within a semi-detached dwelling.

A multicell air flow computer program is used to determine the influence of 1) open windows and 2) closed internal doors on the ventilation rate of a semi-detached house. The changes in interzone air movement and room air change rates are also examined. Tracer gas field measurements used to validate the multicell program show good agreement with the predicted values. Results show that opening windows can alter significantly, not only the overall ventilation rate of the building, but also the individual air change rates in rooms.

The ventilation rate and airtightness of the covered public swimming bath at Wetteren. De ventilatie in en de luchtdichtheid van het overdekt gemeentelijk zwembad teWetteren.

Describes the measurement of air change rate and airtightness of a mechanically ventilated public swimming bath in Belgium. The relationship between airtightness and air change rate is outlined. Various methods of calculating the air leakage from the pressurization results are compared. Nitrous oxide was used for the tracer gas measurements, which were made both with and without the mechanical ventilation system working. The LBL model was used to calculate the air infiltration rate.

The physical reasons for the appearance of draughts - new findings. Physikalische ursachen fur zugerscheinungen - neue erkenntnisse.

Presents a mathematical model for the measurement of thermal comfort. Compares the results with previous measurements of air velocity in buildings with and without air conditioning.

Investigating natural air flows on the basis of similarity theory in covered spaces with floor heating. Untersuchung von naturlichen luftstromungen in fussbodenbeheizten hallenbauten auf der grundlage der ahnlichkeitstheorie.

Describes qualitative experimental investigation of the air flow in a scale model representing a typical, average hall. Smoke was used to display the air flows. A mathematical model was also developed. Determination of the turbulent air flow in the model confirms the suitability of the mathematical model foruse in quantitative experiments, in particular for measuring the heat flux density.