Energy-Efficient Dehumidification for Greenhouse Buildings via Subcooling Regulation Strategies in Thermoelectric Systems

To investigate the influence of fin–wall subcooling regulation on moist-air condensation dehumidification, this study numerically investigates the dehumidification performance and energy response of a thermoelectric cooling system under three subcooling control strategies: gradient subcooling, frequency-modulated subcooling, and amplitude-modulated subcooling. Under strictly identical gas-phase parameters and geometric conditions, the moisture removal rate per unit area, the friction-mass-transfer factor, and the moisture-removal energy efficiency are adopted as evaluation indicators. The results show that gradient subcooling exerts a pronounced non-monotonic influence on dehumidification performance, with an optimal subcooling range around 32–33 K. Further increases in subcooling lead to reduced dehumidification performance accompanied by significantly increased energy-related indicators, indicating a transition toward a high-energy, low-benefit operating regime. Compared with gradient subcooling, frequency-modulated subcooling provides a more favorable balance between dehumidification performance and energy efficiency under relatively high subcooling conditions, demonstrating a clear frequency–subcooling coupling effect. In contrast, amplitude-modulated subcooling plays only a secondary role and shows limited influence on both dehumidification performance and energy-related indicators within the investigated parameter range.