Structure (contactor internals, mesh, laminate) is carried as a mass ratio to sorbent with its own c_p — the same m_str·c_p,str term as the Simplified DAC energy model; it adds to the bed thermal mass and so to the sensible duty. The wall follows a first-order approach to T_des (heating) or T_amb (all other steps) and offers no thermal resistance of its own — the bed couples to it through the volumetric coefficient U_a. The LDF sliders set k at 20 °C; a nonzero activation energy scales each coefficient with the instantaneous bed temperature as k(T) = k₂₀ exp[−E_a/R (1/T − 1/293.15)] (Arrhenius), so desorption at T_des is faster than capture at ambient; E_a = 0 reproduces the constant-k model exactly.