Journal of Brilliant Engineering (BEN)

Merve Kurt

This study numerically presents the design of a multi-band metasurface-based microwave absorber designed to operate in the S, C, X, and Ku bands. The proposed structure exhibits simulated peak absorption values above 95% at resonance frequencies of 2.9 GHz, 6.3 GHz, 11.7 GHz, and 17.5 GHz, with narrowband fractional bandwidths of 0.64–1.14%. Polarization sensitivity was evaluated under normal incidence, while angular stability was assessed for Transverse Electric (TE) and Transverse Magnetic (TM) modes under oblique incidence. In addition, the structure was analyzed at oblique incidence angles of 15°, 30°, 45°, 60°, and 75° for TE and TM modes, showing that high absorption performance is generally maintained up to 60° incidence. To further interpret the absorption mechanism, effective permittivity and effective permeability were retrieved at the resonance frequencies; because the design is metal-backed, these parameters are treated as qualitative indicators of the electric and magnetic resonances rather than bulk constitutive parameters. Normalized impedance analysis confirms good matching with free space, with the real part approaching unity and the imaginary part approaching zero at all four resonances. In addition, electric field, magnetic field, and surface current distributions were analyzed at each resonance frequency, revealing anti-parallel current loops between the patterned resonator and the ground plane that confirm the magnetic-resonance mechanism underlying the absorption response. An equivalent circuit model (ECM) was additionally constructed in ADS to verify the reliability of the simulation results, yielding a reflection coefficient (S11) response consistent with the CST Microwave Studio results.

https://doi.org/10.36937/ben.2027.41158

Burak Dumlu Taner Tekin

In industrial ethanol production, distillation and rectification columns are among the most critical units in terms of process energy consumption. In this study, the product column of an industrial-scale ethanol production plant was modeled using ChemCAD software, and the effects of fundamental operating parameters on column performance were investigated. NRTL was selected as the thermodynamic package for the modeling work; the feed stream liquid volume component ratios were defined as Water: 0.91667, Ethanol: 0.08312, and Methanol: 0.00021. In the 60-trays product column, the reflux ratio (R/D), feed tray position, and feed temperature parameters were investigated using a single variable approach. The top product ethanol concentration (vol%), bottom product ethanol loss (vol%), and column energy consumption (MW) were evaluated as performance criteria. Simulation results showed that increasing the reflux ratio improved product purity but significantly increased energy consumption; raising the feed tray position reduced bottom product losses; and increasing the feed temperature resulted in a significant decrease in energy consumption. As a result of the multi-criteria evaluation, the most favorable operating conditions identified in this study to be a reflux ratio of R/D=6, a feed tray of 21, and a feed temperature of 55°C. It was assessed that the determined parameter set provides an favorable balance between product purity and energy consumption and The identified operating conditions provide a favorable balance between ethanol purity and energy consumption within the investigated operating range.

https://doi.org/10.36937/ben.2027.41134