What is the pressure drying mode? Understand the optimal level

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The Pressure drying mode is one of two drying options for the sublimation dryer, Currently, we all choose this drying mode to ensure the optimal and fastest drying process. In this content we will learn more to clearly understand how the machine operates when using this drying mode.

Pressure-based drying controller on Mactech freeze dryer

The freeze dryer is a device that dries brittle products based on 3 main factors, including: 1 is the pressure level in the drying chamber, 2 is the freezing temperature of the product and 3 is the dry temperature of the product at the end of drying process. Having said that, you probably don’t understand, but we have analyzed many of these parameters in previous content for users to have as reference. See more in the content on how to monitor the operation of the freeze dryer to see the changing steps in the drying process from A to Z.

The fast or slow drying speed of a product will depend on the sublimation rate of ice (also known as the evaporation rate) in the product, The fast or slow sublimation rate will depend on the heat is supplied to the product quickly or slowly during the heating drying stage.
In the pressure drying mode, the pressure value in the drying chamber is used as a milestone (threshold) to decide the product heat increase is fast or slow, as long as good product quality is ensured.

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The parameters displayed on the control screen are simplified for users to conveniently follow. Towards the end, the product temperature increases and the drying chamber pressure drops further.

There is a very important relationship between the pressure in the drying chamber and the sublimation of ice in the product. That is, when the product heat is increased too quickly, the ice sublimates too quickly, leading to an increase in drying chamber pressure. If the pressure increases uncontrollably, for example to about 200~500pa, the ice will gradually turn into liquid, which will cause the product quality to decrease. Therefore, there is a pressure value that is controlled so that the machine always operates properly, which is called sublimation pressure. This pressure threshold is usually set at 50pa which is appropriate. Lower is better but drying will be slower, but if set higher it should not exceed 100pa.

Pressure drying mode is the optimal drying mode, When the pressure in the drying chamber is always below the threshold of 50pa (for example), increasing the heat for the product will be done continuously so that the sublimation process of ice occurs the most and fastest.. But if that causes the pressure to increase beyond 50pa, the machine will stop providing heat. For every time below 50pa, the machine will continuously provide heat. Towards the end of drying process, the amount of ice remaining in the product will gradually decrease, then the amount of steam released from the product will not be as much as at the beginning, so the pressure will gradually decrease to a low level (about 20pa), then the 50pa threshold is no longer used.

This parameter (sublimation pressure) is set on Mactech‘s freeze dryer, so other dryer brands on the market may not have this parameter.

The máy sấy thăng hoa website (Vietnamese name) provides information about freeze drying for all types of products in both English and Vietnamese so that users can easily find product drying information.

So you understand what pressure drying mode is. If you don’t understand clearly, please contact Mactech Việt Nam so we can answer directly. Through this, if Customers need advice on how to dry the product effectively, please contact via Hotline, thank you for learning the shared content.

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