Modelling Particle Deagglomeration in Dry Powder Inhalers

Phillips, Timothy (2011). Modelling Particle Deagglomeration in Dry Powder Inhalers B.Sc Thesis, School of Engineering, The University of Queensland.

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Author Phillips, Timothy
Thesis Title Modelling Particle Deagglomeration in Dry Powder Inhalers
School, Centre or Institute School of Engineering
Institution The University of Queensland
Publication date 2011
Thesis type B.Sc Thesis
Supervisor Matthew Cleary
Total pages 112
Language eng
Subjects 0913 Mechanical Engineering
Formatted abstract
Dry powder inhalers or DPIs are an effective method of drug delivery for several diseases and hold promise for improving the treatment of many other diseases. The full potential of DPIs is not realised due to dosage variability and low fractions of the dispensed medication arriving at the target area. These problems are due to the formation of powder agglomerates of sizes unsuitable for passage to the target area. In principle, DPI design can be improved to decrease the dosage variability and increase the fraction of dosage reaching the target area. The physical mechanisms responsible for deagglomeration are not entirely understood although turbulent shear forces acting on the particles have been shown to have a large effect.

The particle size distribution resulting from the action of turbulent shear forces on fine powders has been investigated for a steady flow deagglomeration device. A model of this device was produced with Computational Fluid Dynamics simulation and a Probability Density Function formulation of the Population Balance Equation was applied to the output of this with a Lagrangian Particle Monte Carlo Simulation. The model of particle breakage used in the Population Balance Equation is the power law model with, following the work of other authors, shear rate exponent of 1.85. The predictions of the resulting particle size distribution were compared to experimentally recorded data of the same quantity. The results of this simulation were found to be in disagreement with the observed particle size distribution however qualitative trends were correct. The disagreement between the theoretical and experimental particle size distribution is caused by the chosen value of shear rate exponent being inappropriate for use with the powders under investigation. Agglomeration of particles was found to have negligible impact on the predicted particle size distribution when the isotropic turbulence model of agglomeration was employed in this situation.

Future research areas on this topic have been identified to be improving the property interpolation scheme to better reflect the same method used by the computational fluid dynamics simulation, altering the particle positioning algorithm to improve accuracy, additional research into the physical mechanisms responsible for deagglomeration, improving the representation of breakage processes by the Population Balance Equation and incorporating the effects of particle inertia into the simulation.
Keyword Dry Powder Inhaler

Document type: Thesis
Collection: UQ Theses (non-RHD) - UQ staff and students only
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Created: Tue, 23 Dec 2014, 10:16:26 EST by Ahmed Taha Siddiqui on behalf of Scholarly Communication and Digitisation Service