Air dehumidification performance study of a desiccant wheel by a three-dimensional mathematical model

Abstract

Hitherto air-conditioners have severe shortcomings because of the inherent need to maintain the cooling coil temperature significantly below the air's dew point. Their energy efficiency can be improved by employing desiccant wheel dehumidifiers that offer independent humidity control. Although numerous experimental and theoretical studies have evaluated desiccant wheels’ performance, no existing investigation yields a detailed account of its localized temperature and humidity distributions. Therefore, a new three-dimensional mathematical model was developed to study the time-dependent and steady-state temperature, humidity, and reaction distributions. The model predicted the performance with the maximum discrepancy of ±10% in both temperature and humidity ratio. It also revealed that the countercurrent airflow configuration has a more uniform reaction distribution than the concurrent configuration. The parametric analysis using the model revealed that higher regeneration temperatures require smaller regeneration angles. With the regeneration temperatures ranging between 110 and 50 °C, the optimal regeneration angles span 120–180°. Additionally, the dehumidification performance could be easily improved by increasing the wheel's rotation speed at low desiccant mass since coating more desiccant on the wheel is costly and inconvenient.