Heat Transfer Scale-Up Considerations

It is important to add heat transfer scale-up considerations to the scale-up approach for liquid parenteral solutions as heat transfer applications may play a considerable role in preparation of these products. For heat transfer applications, constant horsepower per unit volume is used to achieve approximately similar heat transfer coefficients for the same type of impeller. This approach is a close approximation since the effect of horsepower on the heat transfer coefficient (ho) is relatively small  

Therefore, even a moderate error in the mixer scale-up will have only a small effect on the agitator-side heat transfer coefficient. Other factors that include heat transfer area per unit volume are considerably more significant. For instance, in the jacketed tank, the heat transfer area per unit volume decreases upon scale-up. In order to assure the same proportionate heat removal or addition per unit batch size, additional heat transfer area (e.g., coils) may be required. Additionally, other variables such as temperature driving force may have to be adjusted to compensate for decreased heat 

Typical Agitator-Side Heat Transfer Coefficients of Organic Fluids 

One must also stress the importance of quality considerations during compounding and full adherence to current good manufacturing practices while producing parenteral products. Personnel responsible for the process design and scale-up of the equipment must assure proper documentation 

Cartensen JT, Metha Ashol. Scale-up factors in the manufacturing of solution dosage forms. Pharm Technol 1982 6(ll) 64-77. 

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