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Papers by XU JIE CHEW
Journal of Turbomachinery, 1991
Sealing of the cavity formed between a stationary disk and a rotating disk under axisymmetric con... more Sealing of the cavity formed between a stationary disk and a rotating disk under axisymmetric conditions is considered. A mathematical model of the flow in the cavity based on momentum integral methods is described and this is coupled to a simple model of the seal for the case when no ingress occurs. Predictions of the minimum imposed flow required to prevent ingress are obtained and shown to be in reasonable agreement with the data of Bayley and Owen (1970), Owen and Phadke (1980), Phadke (1982), and Phadke and Owen (1983a, 1983b, 1988). With an empirical constant in the model chosen to match these data, predictions for the minimum sealing flow are shown to be in good agreement with the measurements of Graber et al. (1987). The analysis of Phadke’s data also indicates the measurements for small seal clearances must be viewed with caution due to errors in setting the seal clearance. These errors are estimated to be twice the minimum clearance considered. Seal behavior when ingress o...
Journal of Turbomachinery, 1989
Journal of Process Control, 2005
Crystallization is the main separation and purification process for the manufacturing of drug sub... more Crystallization is the main separation and purification process for the manufacturing of drug substances. Not only does crystallization affect the efficiency of downstream operations such as filtering, drying, and formulating, the efficacy of the drug can be dependent on the final crystal form. Advances in simulation and control algorithms and process sensor technologies have enabled the development of systematic first-principles and direct design approaches for the batch control of crystallization processes. These approaches address different challenges associated with pharmaceutical crystallization control. This paper provides an overview of recent technological advances in the in situ control of pharmaceutical crystallization processes. Implementation of the first-principles and direct design approaches are compared, and their relative merits are explained. Areas of future opportunities for application of advanced control strategies in pharmaceutical crystallization are presented.
Chemical Engineering Research and Design, 2007
Crystallization is the most important unit operation for the separation and purification of chemi... more Crystallization is the most important unit operation for the separation and purification of chemicals in the pharmaceutical and fine chemical industries. Crystallization processes in pharmaceutical active ingredient manufacturing have been traditionally a recipe-based operations, offering little scope for dynamic process control and improvement. With the change in regulatory climate from quality-by-testing (QbT) to quality-by-design (QbD) and with the advent of the process analytical technology (PAT) initiative, it is timely to examine the impact of such quality-based emphasis on crystallization control. In this paper, we review the important recent developments in the control of crystallization process, and discuss their feasibility and scope for implementation in industrial processes. The control methods to achieve different aspects of crystal product quality, including particle size distribution (PSD), crystal habit and polymorphic form, are discussed separately.
Fuel and Energy Abstracts, 1996
Journal of Turbomachinery, 1991
Sealing of the cavity formed between a stationary disk and a rotating disk under axisymmetric con... more Sealing of the cavity formed between a stationary disk and a rotating disk under axisymmetric conditions is considered. A mathematical model of the flow in the cavity based on momentum integral methods is described and this is coupled to a simple model of the seal for the case when no ingress occurs. Predictions of the minimum imposed flow required to prevent ingress are obtained and shown to be in reasonable agreement with the data of Bayley and Owen (1970), Owen and Phadke (1980), Phadke (1982), and Phadke and Owen (1983a, 1983b, 1988). With an empirical constant in the model chosen to match these data, predictions for the minimum sealing flow are shown to be in good agreement with the measurements of Graber et al. (1987). The analysis of Phadke’s data also indicates the measurements for small seal clearances must be viewed with caution due to errors in setting the seal clearance. These errors are estimated to be twice the minimum clearance considered. Seal behavior when ingress o...
Journal of Turbomachinery, 1989
Journal of Process Control, 2005
Crystallization is the main separation and purification process for the manufacturing of drug sub... more Crystallization is the main separation and purification process for the manufacturing of drug substances. Not only does crystallization affect the efficiency of downstream operations such as filtering, drying, and formulating, the efficacy of the drug can be dependent on the final crystal form. Advances in simulation and control algorithms and process sensor technologies have enabled the development of systematic first-principles and direct design approaches for the batch control of crystallization processes. These approaches address different challenges associated with pharmaceutical crystallization control. This paper provides an overview of recent technological advances in the in situ control of pharmaceutical crystallization processes. Implementation of the first-principles and direct design approaches are compared, and their relative merits are explained. Areas of future opportunities for application of advanced control strategies in pharmaceutical crystallization are presented.
Chemical Engineering Research and Design, 2007
Crystallization is the most important unit operation for the separation and purification of chemi... more Crystallization is the most important unit operation for the separation and purification of chemicals in the pharmaceutical and fine chemical industries. Crystallization processes in pharmaceutical active ingredient manufacturing have been traditionally a recipe-based operations, offering little scope for dynamic process control and improvement. With the change in regulatory climate from quality-by-testing (QbT) to quality-by-design (QbD) and with the advent of the process analytical technology (PAT) initiative, it is timely to examine the impact of such quality-based emphasis on crystallization control. In this paper, we review the important recent developments in the control of crystallization process, and discuss their feasibility and scope for implementation in industrial processes. The control methods to achieve different aspects of crystal product quality, including particle size distribution (PSD), crystal habit and polymorphic form, are discussed separately.
Fuel and Energy Abstracts, 1996