Performance enhancement of desiccant wheel dehumidification using a closed-loop independently-cooled purge sector for ultra-low humidity applications

Ultra-low humidity environments required by semiconductor, lithium-ion battery, and pharmaceutical manufacturing demand dew points that condensation dehumidification cannot reliably reach, making desiccant wheels indispensable. Conventional three-sector wheels use a purge sector to pre-cool the desiccant, but its sizing is constrained by a trade-off between lowering process outlet humidity and preserving process airflow while avoiding desiccant rewetting. This study proposes a closed-loop independently-cooled purge sector, in which the purge air circulates within a sealed loop that recovers residual desiccant heat to preheat the regeneration air and is re-cooled before re-entering the wheel. This removes the purge latent load on the main cooling coil, drives the net purge moisture exchange to zero, and permits the loop to be served either by chilled water or by lower-cost cooling tower water. Using a validated, Python-reimplemented model, four configurations were compared by specific energy consumption (SEC) across 0 °C to −35 °C dew points at 120 °C and 140 °C regeneration. The two-sector design proved incapable of entering the deep-dehumidification range, whereas the three purge-equipped configurations were indistinguishable over the mild range. The proposed system using chilled water separated from the conventional design as the requirement tightened and alone reached the −30 °C and − 35 °C targets, extending single-stage deep-dehumidification capability; the cooling tower water variant, despite far cheaper purge cooling, proved unable to follow it that far. Raising the regeneration temperature increased SEC at every target, and a second-law assessment reinforced the same conclusions.