Lyophilization model of mannitol water solution in a laboratory scale lyophilizer

Ravnik, Jure; Golobič, Iztok; Sitar, Anže; Avanzo, M.; Irman, Š.; Kočevar, K.; Cegnar, Mateja; Zadravec, Matej; Ramšak, Matjaž; Hriberšek, Matjaž

doi:10.1016/j.jddst.2018.02.015

Cited by 22 publications

(29 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The freeze-drying process is usually divided into two parts, the primary and secondary drying stage [4]- [6]. The process starts when the frozen substance is subjected to a sudden decrease in system pressure, setting the thermodynamic conditions below the triple point of the solvent (predominantly water) for sublimation to occur.…”

Section: Modeling the Lyophilization Processmentioning

confidence: 99%

“…In order to obtain the governing set of equations, the energy conservation equation is written for the temperature field in the dried and frozen region, while the mass conservation is usually written for the sublimating water in the form of bounded concentration and partial pressure of liquid vapor, and for the inert gas in the form of partial pressure inside the dried region. The computational algorithm, described in Ravnik et al [6], is an example of an effective model for the solution of the temperature and concentration fields of bounded water inside the substance in the vial, together with the solution of the partial pressure distribution of inert gas and moisture vapor inside the porous layer of the filling.…”

Section: Computational Modelmentioning

confidence: 99%

“…The boundary conditions for all three variables, temperature, partial pressure of inert gas and of water vapor, depicted in Fig. 2, are set separately for the primary and the secondary q simulations of lyophilization in a vial [5], [6], [7]. As the stopper is seldom removed from the vial, its presence acts as an additional hydraulic resistance to the flow of the sublimated vapor, leading to increased pressure values for the evaporated solvent at the exit from the vial.…”

Section: Computational Modelmentioning

confidence: 99%

“…A dedicated model for the sublimation of the surface crystals is therefore needed in order to account for the consumed drying time for the initial 2% of the frozen water. Under the assumption that the top layer of ice has approximately the height of 2% of the height of the cake [6], the conditions at the free surface can be approximated as a single layer of ice crystals, and the sublimation model of ice crystals can be designed by considering a direct contact with the gas space of the vial.…”

Section: Model Of Surface Sublimationmentioning

confidence: 99%

“…In order to obtain the pressure drop that occurs within the vial and the stopper geometry, a CFD analysis was performed. The ideal way of performing the CFD analysis would be by a direct coupling of heat and mass transfer computation of the process inside the vial filling, by using a dedicated computational model [6], [7] and a full 3D CFD analysis of vapor flow through the interior vial duct with the stopper. As this would require the derivation of a new computer program, a simplified approach was adopted.…”

Section: Fluid Flow Modelmentioning

confidence: 99%

See 4 more Smart Citations

The Influence of a Vial Stopper on Flow and Mass Transfer Conditions Inside a Vial

Hriberšek

Zadravec

Časar

et al. 2018

Advances in Fluid Mechanics XII

View full text Add to dashboard Cite

In the process industry, vacuum-type dryers are becoming increasingly important. A special case of vacuum drying is lyophilization, where a solution, containing up to 90% of solvent (typically water), is dried under the conditions of very low temperatures and extremely low system pressures. As a container type, in which the solution is dried, a vial is frequently used. The intensity of drying is to a large extent controlled by the pressure conditions above the drying surface. The vial and the rubber stopper geometry present a significant pressure drop in the flow of sublimated solvent, but are experimentally difficult to determine. In order to produce realistic pressure conditions for the mass transfer computation, a CFD analysis of flow inside the vial-stopper channel is performed. The influence of imposing the no-slip and slip conditions on the solid surfaces on the pressure drop in the system is studied under the typical sublimation conditions. The effect of the increased partial pressure of the solvent on the sublimation rate is calculated by implementing the Maxwell-Stefan diffusion model.

show abstract

Section: Modeling the Lyophilization Processmentioning

confidence: 99%

Section: Computational Modelmentioning

confidence: 99%