rom the above theoretical analysis, we can see that there are many factors that affect the microwave drying quality of wood. From the internal factors, there are not only the reasons for the great difference of dielectric properties between different parts of wood caused by the uneven wood properties and water content distribution, but also the reasons of the uneven distribution of electromagnetic field and the limited penetration depth of electromagnetic wave produced by microwave drying equipment. From the external factors,
there are many reasons, such as the power of microwave radiation is too large, radiation time is too long, the external air velocity is too fast and so on. Therefore, starting from the above theoretical analysis, the following measures can be taken to prevent the occurrence of drying defects in wood microwave drying.
1) In terms of internal factors, the wood microwave dryer, especially the microwave drying chamber, can be optimized to select the appropriate microwave frequency,
improve the uniformity of microwave electromagnetic field distribution in the chamber, and improve the monitoring and control system. There are five specific measures: first, choose the appropriate microwave frequency, microwave frequency directly affects the penetration depth of microwave in wood, with the increase of microwave frequency, the penetration depth in wood decreases. Considering that the working frequency of microwave used in industrial microwave heating is generally 915 MHz or 2 450 MHz, and that microwave drying is mainly used for drying hard-dried wood with large thickness, it is suggested that the working frequency of microwave should be 915 MHz in order to improve the wear of microwave in wood when designing and manufacturing wood microwave drying equipment.
1) In terms of internal factors, the wood microwave dryer, especially the microwave drying chamber, can be optimized to select the appropriate microwave frequency,
improve the uniformity of microwave electromagnetic field distribution in the chamber, and improve the monitoring and control system. There are five specific measures: first, choose the appropriate microwave frequency, microwave frequency directly affects the penetration depth of microwave in wood, with the increase of microwave frequency, the penetration depth in wood decreases. Considering that the working frequency of microwave used in industrial microwave heating is generally 915 MHz or 2 450 MHz, and that microwave drying is mainly used for drying hard-dried wood with large thickness, it is suggested that the working frequency of microwave should be 915 MHz in order to improve the wear of microwave in wood when designing and manufacturing wood microwave drying equipment.
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