Untilted edge slot antennas excited by T-shaped wires

An effective method is proposed to excite the untilted edge slot antennas. In the proposed method, two T-shaped wires are placed at both sides of each untilted slot. Two legs of each T-shaped wire are connected to the waveguide walls, while the third leg is open. One of the T-shaped wires connects the upper broad wall of the waveguide to the narrow wall of the waveguide which contains the slots. Similarly, the other T-shaped wires connect the lower broad wall of the waveguide to the narrow wall of the waveguide that contains the slots. The phase reversal between the adjacent slots can be accomplished by changing the orientation of the T-shaped wires. It is shown that the arm lengths of the connected wires can be employed as a parameter to control the radiated power by the slots. Furthermore, the arm lengths of the open wires can be selected properly to control the dynamic range of the equivalent normalized susceptance associated with each untilted slot antenna. To validate the effectiveness of the proposed antennas, two linear arrays consisting of 11 slots have been designed, implemented, and tested. The simulation and the measurement results of the designed arrays show that for the proposed untilted edge slot antennas, the dynamic range of the equivalent normalized susceptance is improved significantly which leads to a straightforward design process with no requirement to resort to any time-consuming tuning process.

Effect of Reactor Thickness on Gas-Solid Flow and Heat Transfer of Thin Rectangular Fluidized Bed Reactors for CO2 Capture

Thermal design of dual circulating fluidized bed reactors for carbon dioxide (CO2) capture was carried out. To handle large heat duties for regeneration, a thin rectangular reactor was proposed. For feasible thermal design, the effect of varying reactor thickness on the gas-solid flow and heat transfer of the thin rectangular fluidized bed was investigated. Reactor thickness of 10, 30, and 60 mm was tested. Numerical simulations were conducted to analyze the pressure difference, solid particle hold-up distribution, particle velocity, granular temperature, and heat transfer in detail. According to our results, when the reactor is between 10 mm and 30 mm thick, a large solid hold-up occurs adjacent to the narrow wall. This causes a large pressure difference due to the wall effect. Furthermore, the particle velocities were analyzed to evaluate that there is the two-dimensional (2D) particle mixing behaviors. On the other hand, in the case of reactors with a thickness of 60 mm, tuning flows occur adjacent to the narrow wall. This reduced the pressure difference and the three-dimensional (3D) particle mixing behaviors. This difference in particle behavior affected heat transfer. In the case of reactor thicknesses between 10 mm and 30 mm, the heat transfer increased with the reactor thickness. In particular, the heat transfer at the narrow wall of the reactor with a thickness of 10 mm was extremely low due to the low particle mixing. On the other hand, there was more heat transfer with a thickness at the 60 mm wall, despite the low solid hold-up.