Study of a simplified heat transfer model for the ventilated roof desiccant bed

Solid desiccant technologies offer a promising route to low-carbon dehumidification, but most existing systems are stand-alone units that require high-grade regeneration heat, auxiliary fans or pumps, and dedicated plant space. This study investigates a ventilated roof desiccant bed directly integrated into an inclined roof, which combines thermal insulation with nighttime indoor dehumidification and enables fully passive, solar-driven daytime regeneration. To support efficient performance analysis and design, a simplified heat transfer model is developed using a lumped resistance network that represents the metal frame, desiccant layer, and channel air by a set of characteristic temperature nodes. The equivalent thermal resistances are identified using a differential evolution algorithm based on 10 days of measured summer weather in Wuhan, China. The simplified model is further validated under two representative meteorological scenarios (clear-sky and overcast days). Across all cases, the mean absolute error of characteristic node temperatures remains below 1.2 °C (0.5 °C for the overcast day), while the mean absolute error of the internal surface heat flux is below 2 W m−2 and the mean absolute percentage error during peak solar hours is about 2.9%. Compared with the reference COMSOL model, the proposed simplified model reduces computation time by roughly three orders of magnitude while preserving high fidelity, making it well suited to parametric studies, long-term performance assessment, and future coupled heat and moisture analyses of the ventilated roof desiccant bed.