Drying machine technology has a wide range of service areas. Faced with numerous industries, materials with different physical and chemical properties, product quality, and other diverse requirements, drying equipment technology is a cross industry, interdisciplinary, and experimental scientific technology.

Generally, knowledge and skills in three aspects are required for the development and application of drying technology. One is to understand the physical and chemical properties of the dried material and the usage characteristics of the product. The second is to be familiar with the principles of transfer engineering, including mass transfer, heat transfer, fluid mechanics, and aerodynamics, which are the principles of energy transfer. The third requirement is to have means of implementation, which includes engineering design for drying processes, main equipment, electrical instrument control, and other aspects. Obviously, these three aspects of knowledge and technology do not belong to the same disciplinary field. In practice, knowledge and skills in these three aspects are indispensable. So drying technology is a cross industry and interdisciplinary technology.

Although modern dryer technology has a development history of over a hundred years, it still belongs to the category of experimental science. Most drying equipment technologies currently lack scientific theories and design methods that can accurately guide practice. In practical applications, relying on experience and small-scale experimental data is still the main way to guide. The reasons for this situation are as follows:

One of the reasons is that the basic disciplines on which drying technology relies (mainly disciplines belonging to the field of transmission engineering) themselves have the characteristics of experimental science. For example, the development of aerodynamics research still relies on "wind tunnel" experiments, which indicates that it has not yet departed from the scope of experimental science. And the development level of these basic disciplines directly affects and determines the development level of drying technology.

The second reason is that many drying processes involve the intersection of multiple disciplines and technologies, involving a wide range of variables and complex mechanisms. For example, in the field of spray drying technology, the trajectory of atomized droplets in the drying tower is the key to engineering design. The trajectory of a droplet is related to its own volume, mass, initial velocity and direction, as well as the flow velocity of other droplets and hot air around it. But these parameters are undergoing changes due to the processes of mass and heat transfer. Moreover, in the initial state, neither the size of droplets nor the distribution of hot air can be uniform. Obviously, relying solely on theoretical calculations for engineering design of such a complex and variable process is unreliable.

The third reason is that the types of materials being dried are diverse, and their physical and chemical properties are also different. Different materials may have significant differences in their mass and heat transfer rates even under the same drying equipment conditions. If not treated differently, it may lead to unsatisfactory consequences. For example, in the drying process of certain Chinese herbal medicines, even if they belong to the same type of herb, the drying conditions must be changed due to differences in their origin or harvest period, otherwise the product quality will be substandard.

The above three reasons determine that the development and application of drying technology should be based on experiments. However, these characteristics of drying equipment technology are often intentionally or unintentionally overlooked by people. Manufacturers often avoid conducting necessary drying experiments due to a lack of testing equipment or incomplete types (which is a common phenomenon in China), while users often abandon the requirement to conduct necessary tests due to a lack of understanding of the characteristics of drying technology. The outcome is that the device has poor performance and may even be scrapped. In our country, such cases are not uncommon. There was a lesson learned from a set of industrial drying equipment worth 20 million yuan being idle due to failure to meet usage requirements. Therefore, before constructing industrial drying equipment, especially larger ones, it is necessary to conduct sufficient and convincing tests, and use the test results as the basis for the construction of industrial equipment. This is a significant characteristic of the application of drying technology.