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A cross-industry assessment of the flow rate-elapsed time profiles of test equipment typically used for dry-powder inhaler (DPI) testing: Part 2– analysis of transient air flow in the testing of DPIs with compendial cascade impactors
journal contribution
posted on 2020-07-16, 13:26 authored by Hendrik Versteeg, DL Roberts, F Chambers, A Cooper, M Copley, JP Mitchell, H MohammedWe describe a computational model that captures the physics of the unsteady airflow start-up that accompanies the testing of dry-powder inhalers (DPI) with cascade
impactors (CIs) specifically when following methods described in the pharmacopeial
compendia. This transient has been measured in a multi-organization study for a wide
range of conditions and reported in a companion article. The DPI test system is simulated
as a series of flow resistances, starting with the inhaler itself, including each stage of the
CI, and finishing with the prescribed flow control valve, wherein the flow is held at sonic
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velocity. The resulting non-dimensional equations indicate the relative importance of the
several flow resistances. The model agrees well with the available experimental data for
the Next Generation Impactor (NGI™) and qualitatively with the available data from a
variety of the configurations of the Andersen 8-stage cascade impactor (ACI), including
the typical 4-kPa pressure drop across an entry fixed orifice mimicking surrogate low-,
medium- and high-resistance DPIs. The model indicates that the start-up times for the
NGI and for the ACI are very reasonably estimated by a simple “reference time,” given in
equation (26) and, for an inlet flow rate of 60 L/min, having a value of 277 ms and 113
ms for the NGI and ACI (60-L/min configuration), respectively. The model also enables a
baseline, universal design curve for the flow rise-time performance of testing DPIs with
the NGI (Figures 9a,b), because this impactor requires no change of components for any
inlet flow rate.
History
School
- Mechanical, Electrical and Manufacturing Engineering
Published in
Aerosol Science and TechnologyVolume
54Issue
12Pages
1448 - 1470Publisher
Taylor and FrancisVersion
- AM (Accepted Manuscript)
Rights holder
© American Association for Aerosol ResearchPublisher statement
This is an Accepted Manuscript of an article published by Taylor & Francis in Aerosol Science and Technology on 14 August 2020, available online https://doi.org/10.1080/02786826.2020.1792825Acceptance date
2020-06-18Publication date
2020-08-14Copyright date
2020ISSN
0278-6826eISSN
1521-7388Publisher version
Language
- en
Depositor
Mr Hendrik Versteeg . Deposit date: 14 July 2020Usage metrics
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