How Vial Geometry Variability Influences Heat Transfer and Product Temperature During Freeze-Drying

Vacuum freeze-drying technology is applicable to the process of high heat-sensitive products. Due to the long drying period and extremely low processing temperature and pressure, the uniform and efficiency of heat transfer fluid temperature in shelf are critical for product quality. Therefore, in this study, the commercial computer fluid dynamics (CFD) software, FLUENT, was utilized for three-dimension numerical simulation of the shelf vacuum freeze-drying process. The influences of different inlet and outlet positions for shelves on the uniformity of the flow rate and temperature were discussed. Moreover, it explored the impacts on the temperature gradient of shelves after heat exchange of different flow rates and low temperature materials. In order to reduce the developing time and optimize the design, the various secondary refrigerants in different plies of shelves were investigated. According to the effect of heat exchange between different flow rates and low temperature layer material shelves on the temperature gradient of shelves surface, the minimum temperature gradient was 20 L/min, and the maximum was 2.5 L/min.

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Molded Vial Manufacturing and Its Impact on Heat Transfer during Freeze-Drying: Vial Geometry Considerations

AAPS PharmSciTech ◽

10.1208/s12249-021-01926-x ◽

2021 ◽

Vol 22 (2) ◽

Author(s):

Tim Wenzel ◽

Henning Gieseler

Keyword(s):

Heat Transfer ◽

Contact Area ◽

Freeze Drying ◽

Thermal Characteristics ◽

Heat Transfer Characteristics ◽

Transfer Parameter ◽

Manufacturing Technique ◽

Transfer Characteristics ◽

Heat Transfer Parameter ◽

Glass Compositions

AbstractRecent advances in molded vial manufacturing enabled manufacturers to use a new manufacturing technique to achieve superior homogeneity of the vial wall thickness. This study evaluated the influence of the different manufacturing techniques of molded vials and glass compositions on vial heat transfer in freeze-drying. Additionally, the influence of using empty vials as thermal shielding on thermal characteristics of edge and center vials was investigated. The vial heat transfer coefficient Kv was determined gravimetrically for multiple vial systems. The results showed superior heat transfer characteristics of the novel manufacturing technique as well as differences in heat transfer for the different glass compositions. Empty vials on the outside of the array did not influence center vial Kv values compared to a full array. The direct contact area and vial bottom curvature and their correlation to heat transfer parameters were analyzed across multiple vial systems. A new approach based on light microscopy to describe the vial bottom curvature more accurately was described. The presented results for the contact area allowed for an approximation of the pressure-independent heat transfer parameter KC. The results for the vial bottom curvature showed a great correlation to the pressure-dependent heat transfer parameter KD. Overall, the results highlighted how a thorough geometrical characterization of vials with known heat transfer characteristics could be used to predict thermal characteristics of new vial systems as an alternative to a time-consuming gravimetric Kv determination. Primary drying times were simulated to show the influence of Kv on drying performance.

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785. Water vapour and heat transfer during vacuum freeze drying, with reference to optimal process conditions

Vacuum ◽

10.1016/0042-207x(67)91678-8 ◽

1967 ◽

Vol 17 (4) ◽

pp. 250

Keyword(s):

Heat Transfer ◽

Water Vapour ◽

Freeze Drying ◽

Process Conditions ◽

Optimal Process

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Impingement Cooking of Meat Products: Effect of Variability on Final Temperature

Food Science and Technology International ◽

10.1177/1082013208095515 ◽

2008 ◽

Vol 14 (3) ◽

pp. 241-250 ◽

Cited By ~ 2

Author(s):

K. Cronin ◽

J. Caro-Corrales ◽

J. Tobin ◽

J. Kerry

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Input Parameter ◽

Meat Products ◽

Dominant Contribution ◽

Final Temperature ◽

Product Temperature ◽

Dimensional Variation ◽

Beef Burgers

Heat transfer coefficient (HTC) for chicken fillets and beef burgers were determined at a number of product-to-tube distances in an impingement air unit. The coefficient varied from < 100 W/m2 K to over 200 W/m2 K depending on the input parameter settings. The level of variation in the coefficient between adjacent product items in the oven has been quantified as ±20 W/m 2 K. Models of sheat transfer for both food products have been developed. Parameter of the models indicated that depending on the product, either dimensional variation in the product or dispersion in the HTC between products can make the dominant contribution to dispersion in final product temperature.

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