Flow leaks normalization

Flow leaks are small devices generating a well-determined flow when subject to a pressure differential (feed pressure). Though, they need to be calibrated against a reference flow based on the feed pressure and fluid density through a complex relation derived from the modified Darcy law, therefore results of a calibration performed in a given condition are not necessarily valid when the leak is used in different conditions. In this paper we will describe a correct renormalization of the calibration results allowing to compute precisely the actual flow rate generated by the leak. A mathematical description of the renormalization will be presented and a method for the experimental determination of the permeability will be discussed. It will be shown that the calibration uncertainty can be reduced by applying the correct normalization, and that the in-use uncertainty can be brought to be of the same order of magnitude as the calibration uncertainty.