This study investigates the transient thermo-fluid behavior of structured packed beds for rock thermal energy storage (RTES) applications using pore-scale modeling. Three representative lattice-based packings are considered: simple cubic (SC), body-centered cubic (BCC), and face-centered cubic (FCC). For each configuration, periodic structured geometries are generated and discretized with conformal meshes designed to resolve conjugate heat transfer at pore-scale and interstitial flow features. The governing Navier-Stokes and energy equations are solved to obtain detailed velocity and temperature fields, enabling direct assessment of local and transient transport mechanisms that are later used to refine the correlations for continuum porous-medium models. The analysis focuses on transient operation across charging, storage, and discharge phases. Particular attention is paid to high-temperature regimes where radiative component is the main contributor to the effective thermal transport through void spaces and solid surfaces. Surface-to-surface radiation modeling is incorporated for this purpose, and to quantify its impact relative to convection and conduction. The resulting dataset allows systematic comparison of SC, BCC, and FCC arrangements in terms of pressure-drop behavior and heat transfer effectiveness which will find application in thermal stratification preservation during storage and utilization factor during charging and discharging. Moreover, the pore-scale results are used to refine effective porous media properties suitable for larger-scale packed-bed simulations. The outcomes provide design guidance for selecting and optimizing structured packed-bed arrangements for RTES systems, supporting improved multiscale models and more reliable engineering design at high temperatures.