The microwave heating and drying equipment
As a prelude to the design work of the online microwave wood drier, simulations
were performed by Risman [33] using the QW3D software in order to optimize
the field distribution in the cavity, i.e., to determine the cavity dimensions to
achieve as even heat distribution as possible. The field distribution, and
consequently the heat distribution, depends on the design of the cavity [34]. The
electromagnetic waves interfere with each other in the cavities and thereby give
rise to a specified electric field within the space. The cavity or applicator that was
developed for wood drying is not quite a single-mode cavity. Actually, there is a
supplemental mode that allows the heat distribution to extend further in the
longitudinal direction (figure 3 in Paper II). This will decrease the crosstalk
between the cavities. Crosstalk means that the fields in the different cavities affect
each other disadvantageously and out of control. It is for that reason of great
importance to minimize this effect. The heat distribution in the cavities gives rise
to longitudinally directed hotter spots in the wood load (figure 19). The balance
between these spots is affected or caused by two vertical and two horizontal strip
plates (figure 3 in paper II) that also reduce the crosstalk. The heat distribution
shown in figure 19 was captured by an IR camera (AGEMA 550).