Conference Agenda

Duct air leakage tests -DALT- carried out on air systems today are carried out according to the procedures prescribed by specific International Standards. All these Standards, without exception, refer to a model that estimates leakage as a function of a leakage coefficient (f) multiplied by the leakage area value (A) and the static overpressure value elevated to an exponent n assumed constant and equal to 0.65. This model is a simplified form of a more general model that also requires determining the leakage exponent n.

Within certain limits, the simplified model fulfills the classification requirements but does not prove reliable for the analysis of leaks under operating conditions and, thus, for verifying the increase in energy consumption.

For such purpose, the application of the full model appears to be necessary; this requires the identification of a different test procedure capable of obtaining the information needed to determine not only the f- value but also the n - value.

The paper is focused on the proposal of a procedure useful for the characterization of the full model as well as a methodology for calculating the f and n parameters borrowed from that currently applied for the characterization of air leakages in buildings. Finally, the paper proposes a method to transfer the results obtained by the new procedure back to the information useful for classification, thus allowing the old procedure to be fully replaced without losing the applicability of the existing standards.

The methodology was applied to a real system and the values were identified.

The procedure presented was developed with the aim of being able to carry out the measurements using the same DALT instruments used to date without requiring replacement.