Heat transfer method on Freeze drying, hot drying and cold drying

Each method of drying products from fruits, vegetables, fish, meat, medicinal herbs, powder solutions… has a different principle or heat transfer method, each heat transfer method will have its advantages and disadvantages and appropriate applications. In this content, we will learn about heat transfer methods to products on freeze dryers, hot dryers and heat pum dryers of Mactech to see the differences between them.

The temperature factor in drying methods is very important because it directly affects the evaporation rate of water in the product, whether the temperature is negative, low or high temperature all have appropriate effects. In each type of dryer, the heat transfer method will be different, depending on the drying principle.

The Common drying methods today include hot drying (with Circulating hot air dryers), heat pump drying, freeze drying (or sublimation drying) and vacuum drying, all of which require the use of temperature to dry the product. With hot drying and cold drying, wind (air) is used to circulate continuously in the machine to transfer heat as well as continuously dry the product surface. That’s why in the image above you will see that on both sides of the machine there are rows of small holes, which is where the hot wind blows out to transfer heat to the product.
So the heat transfer method with convection hot drying is to use circulating air to transfer heat to the product. The drying tray is usually in the form of a perforated plate, a mesh tray, and the more airy the tray, the better.

With Freeze dryers and vacuum dryers, the drying chamber is vacuumed to a very low pressure, so there will be no air in the drying chamber, so the heat transfer method will have to be different from the hot drying or heat pump drying. With current Mactech sublimation dryers, the solvent heat transfer system is mainly used for the highest efficiency.
The cold heat is transmitted from the main cooling system of the machine to the tray support shelf and then transmitted to the drying tray and the product, which is the freezing stage for the product to a cold temperature of -30^oC. During the drying stage, the sublimation stage of ice in the product, the product temperature must gradually increase from frozen to +30^oC or higher. Then the heat transfer solvent system will transfer hot heat from the resistance heater to the drying tray and product.

The contact heat transfer method between the product surface and the drying tray surface is the best and most effective way to transfer heat (hot and cold) in a vacuum environment, so Customers will see the drying tray part of this device is relatively complex and has many details. The drying tray containing the freeze drying products is always a flat tray, 1-2mm thick, solid sheets, it is important to always be very flat so that the contact area with the shelf supporting the tray is always the highest, heat transfer is fastest.

On the interface of this Máy sấy thăng hoa website, there will be full titles and images of each part of the dryer for you to learn in detail.

So with the above basic information, Readers have a better understanding of the current heat transfer methods used in dryers. Customers who need more advice on drying products and suitable dryers, please contact Mactech Việt Nam for detailed information. Thank you for learning the shared content.