Optimization of the Freeze-Drying Cycle: A New Model for Pressure Rise Analysis

Heat Transfer in Freeze-Drying Apparatus

“…product temperature at the beginning of the test, and K v ) are retrieved by looking for the best fit between measured and calculated values of chamber pressure (Milton et al, 1997;Chouvenc et al, 2004;Tang et al, 2006;. The optimal selection of sampling frequency and duration of the test has been discussed by Fissore et al (2011a), who also proposed a modification of the Dynamic Parameters Estimation algorithm to cope with the problem of ill-conditioning.…”

Rapid freeze-drying cycle optimization using computer programs developed based on heat and mass transfer models and facilitated by tunable diode laser absorption spectroscopy (TDLAS)

“…For example, several articles about cycle optimization focus on the pressure rise (PRA) or manometer temperature measurement (MTM) technology. [2][3][4][5] This technology was first reported by Milton et al 3 for the purpose of measuring mean product temperature using a noninvasive approach. Later, Chouvenc et al 4,5 extended the PRA technology to a pilot dryer with a more slowly cycling isolation valve.…”

“…[2][3][4][5] This technology was first reported by Milton et al 3 for the purpose of measuring mean product temperature using a noninvasive approach. Later, Chouvenc et al 4,5 extended the PRA technology to a pilot dryer with a more slowly cycling isolation valve. Using this approach, the following three dependent variables were determined: (1) the ice sublimation interface temperature T p , (2) the mass transfer resistance of the dry layer, and (3) the overall heat transfer coefficient of the vial K v .…”

Computer-Aided Framework for the Design of Freeze-Drying Cycles: Optimization of the Operating Conditions of the Primary Drying Stage

“…Various experimental methods were developed in the past to evaluate Kv and Rp, e.g., the test of pressure rise: the drying chamber is isolated from the condenser for a short time interval (usually ranging from 5-10 to 30 s) closing a valve in the duct connecting the chamber to the condenser and the pressure variation in the chamber, due to water vapor accumulation, is measured. Then, model parameters (Kv and Rp), as well as other variables like product temperature and the residual amount of ice, are estimated looking for the best fit between the values of chamber pressure measured and those calculated using a mathematical model of the process [22][23][24][25][26][27]. As an alternative to this method, it is possible to use Tunable Diode Laser Absorption Spectroscopy (TDLAS) to estimate Kv and Rp, beside product temperature and the residual amount of ice [28][29][30].…”