The pressure drop across packed beds that are rotating differs in significant and unexpected ways, compared to the pressure drop behavior across conventional packed beds. For a wide range of operating conditions, (1) the pressure drop across an irrigated bed can be significantly lower than that across a dry bed and (2) for a fixed outer diameter, increasing the depth (i.e., more transfer units) of a rotating bed can result in a reduction in the pressure drop across the bed. Furthermore, the power required to spin the rotor diminishes as the vapor flow rate increases. Previously published correlations on the pressure drop across rotating beds do not explain or predict these phenomena. Here, a semiempirical sectional pressure drop model is presented, where all of these phenomena are related to the gas phase conserving its angular momentum as it flows from the shell through the rotating bed toward the centrally located exit.