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DIFFERENCE BETWEEN SINGLE DRUM AND DOUBLE DRUM

“Single drum, double drum” are very familiar terms if you are working in the field of coffee roasting or have ever cared a little about coffee roasters.

Today, Mars would like to share a bit of knowledge about the structure, features and differences between these two types of drums so that customers have a deeper understanding to choose the right product for yourself.

Double drum: The drum is welded from 2 layers of materials glued together (can be stainless steel or cast iron or carbon steel, about the MARS ROASSTER roasting drum material mentioned in the previous article), maybe 2 layer of the same material or different materials depending on the purpose of use, in between these two layers is an air layer (called an air cushion).

Single drum: is a drum made of 1 layer of material, molded monolithically and as the name suggests, has only 1 layer.

Through the concept of 1-layer drum, 2-layer drum, we can also imagine the structure of the drum. Next, we need to find out more about the technology you are using for the roaster. Currently, the two most commonly applied technologies are: direct heating technology (direct combustion) and indirect heating technology (hot air).

– Direct combustion technology: is that the flame from the burner is in direct contact with the outer wall of the roasting drum.

– What about hot air technology: that is, heating the air in another location and then the hot air will be pushed into the roasting cage to ripen the coffee beans. In the following article, Marrs will learn more about these two technologies with everyone.

What are the advantages and disadvantages of these two types of drums when applied to direct burning and hot air technology?

Advantages and disadvantages of  Double drum roasting drum when heated directly:

  • Advantages: heat will be transferred from the first layer then to the air cushion – thanks to this layer the heat is evenly distributed on the drum wall, creating a uniform heat in the second layer. Therefore, the coffee is exposed to any temperature. Any point on the drum is equally heated, without scorching the edges.
  • Disadvantage: As everyone knows, solids will transfer heat better than air, the air layer in the middle of the double drum is considered as single drum of insulation. With a double drum we will need a much larger amount of heat to heat the coffee than with single drum, resulting in burning fuel.

Advantages and disadvantages of single layer roasting drum when burning directly:

  • Advantages: Heat is transferred to the drum quickly, saving fuel.
  • Disadvantage: Although it is a drum and the coffee is always stirred continuously during roasting, if we take a closer look, the coffee is heated when it comes in touch with the drum surface, this surface of the bean is in touch but the surface of the bean is exposed. The other side is not. In addition, while stirring, the beans will stack on top of each other, so there will be seeds that are exposed first, heat transfer first or in other words, the beans will heat unevenly, leading to a situation where the beans ripen first. and the seeds ripen later. Moreover, when the seeds are ripe but still in contact with the drum, it will lead to burning.
  • Conclusion: For these reasons, we can conclude that the single drum is not suitable for direct combustion technology. Double drum is the optimal choice for this technology.

Advantages and disadvantages of 2 types of drums when using hot air technology:

In this case, the roasting drum is only responsible for storing and stirring the seeds, not providing heat for the beans (only a small insignificant part). So single or double in this case does not matter.

In terms of mechanics, a monolithic single-layer drum will be much more durable than a double drum because of its completely solid molded structure. In contrast, double drums, if applied in this technology, will give a big disadvantage because it will be difficult to roast according to the profile. The reason is because the double drum holds well, so it is difficult to increase or decrease the heat according to the roaster’s will. So single drums are more suitable for hot air technology than double drums.

  • Conclusion: So single drum is more suitable for hot air technology than double drum.

We can draw the conclusion, each type of drum will be suitable for different heat transfer technology. Your roaster will be optimized using the right materials and technology. So is your roaster optimized yet? Please text and or call Duong Thanh DTC so that we can share what you are interested in. Do not forget to accompany Duong Thanh in the next articles.

Best regards!