# Using Modeling to Select the Type of Microwave Field Emitter for Dense-Layer Grain Dryers
## 3 Results
### Comparison of Radiation Patterns for the Three Types of Emitters Studied  
A comparison of the radiation efficiency values for the three types of waveguides under study showed that the semicircular waveguide has the best data. However, the distribution of radiated power shown in Figures 11b, 13b and 15b does not fully allow us to estimate the change in the distribution of the electromagnetic field along the waveguides. Therefore, Figure 16 shows graphs of directional patterns for three types of waveguides.  
Figure 16 shows the radiation patterns along the waveguide perpendicular to the radiation. The radiation patterns show that the most uniform distribution of the microwave field is observed in a semicircular waveguide. This allows you to make a choice in its favor.  
Figure 16: Radiation patterns for the three types of waveguides under study.  
Figure 15: Results of 3D mathematical simulations for microwave field radiation in the output of semicircle waveguide with slot radiator: (**a**) 3D angular pattern for microwave electromagnetic field and (**b**) 3D density distribution of radiated microwave field.  
In order to confirm the authors' conclusion regarding the comparison of radiation uniformity based on the radiation pattern, further simulations were conducted. The distribution of the microwave field in the wheat grain layer with a moisture content of 14% was modeled. As a result, graphs (Figure 17) of the microwave field absorption along the length (\(z\)-coordinate) and height (\(y\)-coordinate) of the waveguide were obtained.  
The change in the power absorbed by the grain completely corresponds to the change in the radiation amplitude in the radiation patterns.  
Figure 17: Grain absorption of the microwave field radiated by the waveguide (**a**) for a horn waveguide; (**b**) for a rectangular waveguide; and (**c**) for a semicircular waveguide.  
There is a significant difference in the irregularity of radiation between the three types of emitters. Therefore, it is not necessary to use numerical uniformity indices in this case. The use of homogeneity indices will be more meaningful when the difference between the radiation patterns of the electromagnetic field radiation is smaller.  
It should be noted that in the microwave drying of grain, the operating modes of the radiators depend on the grain heating temperature and its current moisture content. The operating modes of the radiators are not constant but vary depending on the results of real-time monitoring of the grain layer's condition. Therefore, the coordination of waveguides is carried out based on the zone of operation within the setup (depending on the moisture content of the processed grain). The coordination of waveguides is assessed using three indicators: standing wave ratio, radiation efficiency, and uniformity of the microwave field distribution. The evaluation of coordination and \"adjustment\" of coordination is performed at the stage of modeling the field propagation in the grain. Thus, this work should be carried out in the next stage of modeling.  
In this case, it will be necessary to consider the placement of waveguides in the microwave-active zone. The mutual arrangement of waveguides and the microwave-convective zone's enclosure will influence the modeling results. Once the best result is achieved through modeling, experimental studies can be conducted.