AIVC - Air Infiltration and Ventilation Centre

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mathematical modelling

Evaluation of ventilation systems through three dimensional numerical computation.

To make an evaluation of ventilation systems, numerical computation was carried out for three dimensional, isothermal, and turbulent flow schemes. It was found that there exists an optimum position for an inlet in relation to an outlet whereby the most effective ventilation can be attained. In addition, similar to the results for the two dimensional computation, the slope of the concentration decay is virtually constant and independent of the position in the room, so the mixing factor derived from this slope can be used as an index of the ventilation efficiency.

Predictions of temperature distributions within spaces with convective heat sources.

Discomfort due to stuffiness and adverse temperature gradients may occur in well insulated rooms with low levels of natural ventilation. Using methods previously applied to studies of convection in the atmosphere, a model of the room air movement

Computation of ventilation currents.

Much research work has been carried out on modelling ventilation air currents. The authors propose that the currents be divided into specific zones, the air parameters of each zone being determined by different conditions. The formula is then derived by the addition of an infinite number of elementary currents flowing from a multitude of point sources. From this, a general formula is proposed to calculate the velocity, temperature and admixture concentration along the whole flow of the current.

Air infiltration and indoor air quality - a critical review.

Covers the factors affecting air infiltration and indoor air quality, the utility of existing air infiltration models, and the ideal and practical requirements of a relevant indoor air quality model that could be used as a tool for management of atmosphere in tightly enclosed residential spaces.

Transient analysis of the thermal and moisture conditions in wall constructions with additional thermal insulation

A transient simulation method TRATMO with applications to the analysis of the hygrothermal behaviour of timber frame constructions with additional thermal insulation is discussed. This method makes it possible to evaluate the hygrothermal behaviour with respect to risks of mouldering since it gives simultaneous information on moisture content and temperature at certain sections of the construction. Based on the computer simulations and experiments a number of practical aspects to be considered in additional thermal insulation of timber frame constructions are introduced.

A state-of-the-art research assessment for residential attic condensation

A brief synopsis of recent analytic and experimental studies is given. Conclusions are that convective transfer of water vapour into an attic from the living space below often transports more moisture than diffusive transfer through the ceiling construction. Large quantities of moisture are stored in the roof sheathing during warm spring and summer periods. Solar loading during mild winter periods can produce desorption of moisture from the sheathing. This paper reviews the formulation of mathematical relationships among physical parameters governing moisture transfer within attics.

Moisture and retrofitted wall insulation in existing houses

Presents the conclusions of several field studies carried out in retrofitted houses in the USA and compares them with predictions from models.

Air infiltration and heat exchange.

Air-to-air heat exchangers were evaluated as a method of maintaining indoor contaminant concentration levels below acceptable levels. A mathematical simulation of air infiltration and indoor contaminant generation was used todetermine the distribution of contaminant concentrations at various average intervals including hourly and yearly. Both spot generation such as from unvented combustion, and diffuse sources, such as from materials, were considered for four contaminants, nitrogen dioxide, carbon monoxide, carbon dioxide and formaldehyde.

A method to analyze the transient hygrothermal behaviour of building materials and components.

A method has been introduced for the analysis of the hygrothermal behaviour of building materials and construction. The model equations for coupled heat and mass transfer used in the computer code TRATMO and in the determination of hygrotherm

Thermal analysis of moisture conditions in multi-layer constructions.

A method to analyze thermal and moisture physical behaviour of building components under transient conditions is introduced. The method is supported by the procedure TRATMO (Transient Analysis of Thermal and Moisture Physical Behaviour of Constr