What brand of dryer is good?
Drying technology has a wide range of applications. In the face of numerous industries, materials with different physical and chemical properties, product quality and other requirements, drying technology is a cross-industry, interdisciplinary, and experimental science technology. Generally, three aspects of knowledge and technology are required in the development and application of drying technology.
The first is to understand the physical and chemical properties of the dried material and the characteristics of the product.
The second is to be familiar with the principles of transfer engineering, that is, the principles of energy transfer such as mass transfer, heat transfer, fluid mechanics and aerodynamics.
Third, there must be means of implementation, that is, engineering design of drying process, main equipment, electrical instrument control, etc. Obviously, these three aspects of knowledge and technology do not belong to one subject area.
Although modern drying technology has a history of more than one hundred years, it still belongs to the category of experimental science. Most drying technologies currently lack scientific theories and design methods that can accurately guide practice. In practical applications, relying on experience and small-scale test data is still the main way to guide.
The reasons for this situation are as follows:
One reason: Some basic disciplines (mainly disciplines under the category of transfer engineering) on which drying technology is based have the characteristics of experimental science. For example, the research and development of aerodynamics must be promoted by "wind tunnel" experiments, which means that it has not deviated from the scope of experimental science. 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 are processes where multiple disciplines and technologies meet, which involve a wide range of areas, many variables, and complex mechanisms. For example, in the field of spray drying technology, the trajectory of the atomized droplets in the drying tower is the key to engineering design. The trajectory of the droplet is related to its volume, mass, initial speed and direction, and the flow velocity of other droplets and hot air around it. However, these parameters are changing all the time due to the progress of mass transfer and heat transfer. Moreover, in the initial state, neither the size of the droplets nor the distribution of hot air can be uniform. Obviously, it is unreliable to only rely on theoretical calculations for engineering design for such a complex and changeable process.
The third reason: the types of dried materials are diverse, and their physical and chemical properties are also different. Even under the same drying conditions, the mass and heat transfer rates of different materials may be quite different. If they are not treated differently, they may cause unsatisfactory consequences. For example, for the drying of some Chinese herbal medicines, although the same medicinal materials are of the same kind, the drying conditions must be changed only because of the differences in the origin or harvest period of the medicinal materials, 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 technology are often overlooked intentionally or unintentionally. Manufacturers often avoid drying experiments that should be done due to lack of test equipment or incomplete types (this is a common phenomenon in our country), and users often give up the requirements for necessary tests because they do not understand the characteristics of drying technology. The result is that the device is not effective or even scrapped. Therefore, before building an industrial drying device, especially a larger device, a sufficient and convincing test must be carried out, and the test results shall be used as the basis for the construction of the industrial device. This is a significant feature of the application of drying technology.