Freeze Drying Chamber

Drying Chamber Shape: It Matters A Lot

When you buy a freeze dryer machine, you must noticed that there are 2 types of drying chamber: Rectangular shape and Cylindrical shape. To select the right one, you should know the features of them, because the chamber really matters a lot, to your product quality, batch duration, cost and application fields. In this article, we will have a complete comparation, so that help you select the right freeze drying equipment.

Production Processing and Cost

Both cylindrical chamber and rectangular chamber starts with a S/S plate, rolling and welding to its final shape.

The cylindrical drying chamber process is quite simple and easy, rolling the plate to cylindrical and then welding it. Later use several steel rings (external welding) to reinforce.

The rectangular drying chamber process need more time. Because it needs corners treatment (rounded) for easy clean in later use period, and it requests complex reinforce structure, since rectangular drying chamber has larger innerstress, easy distortion if poor reinforce.

Rectangular chamber due to its complex process, its cost about 3X higher than cylindrical ones, either labor cost or processing cost.

Rectangular Chamber
Rectangular Chamber
Cylindrical Chamber
Cylindrical Chamber

The Insulation

Rectangular chamber, due to the complex reinforce structure, PUF injection is the only way for insulation, so that anywhere can cover by heat insulation material.

Cylindrical chamber has more choices: PUF, Rubber sponges, Mineral wools etc. easy to cover on it.

The Spacing Using Rate

Rectangular chamber space using rate much higher than cylindrical ones (>25%). The heat-plates stuff into rectangular chamber (with evenly spacing between) almost can full fill it; but cylindrical chamber cannot, a lot space is wasted (between chamber wall and shelf module), some manufacturers try add some smaller size heat-plates in top and bottom part of the shelf module, to increase the space using rate, but still cannot compete with the rectangular ones.

Rectangular Chamber
Rectangular Chamber
Cylindrical Chamber
Cylindrical Chamber

Temperature Uniformity

With a lot empty space, cylindrical chamber is hard to guarantee the temperature uniformity inside it, also because of the empty space around shelf module which caused “Edge Effect”, the heat-plate temperature uniformity also influenced a lot: For a specified heat-plate, center part temperature higher than surrounding; For the entire shelf module, top and bottom heat-plates temperature lower than central ones.

Rectangular chamber, heat-plates temperature uniformity is much better, whatever between heat-plates or between points (in a heat-plate), the variance can control <+/-1C.


Cylindrical chamber is easy to clean, because of the physical advantage, and the large space around the shelf module enable cleaning tools easy to reach any place.

Rectangular chamber, although the corners are rounded, but due to the limit space, cleaning tools almost impossible to reach inside, especially the (upper and bottom) chamber walls.


As mentioned above, rectangular chamber absolutely is better than cylindrical drying chamber, except the cost is higher. But not always, for freeze drying, the selection should be based on application fields:

For common food, fruit, snacks, herbs etc. that not request accuracy temperature control, freeze drying equipment with cylindrical chamber is very suit. Economic price and less production time.

For high value materials and heat sensitive products like bacteria, probiotics, enzymes, probiotics, pharmaceutical APIs and biological ingredients, rectangular chamber freeze dryer may be the right one. Because it offers incomparable temperature uniformity.

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