Effect of velocity ratio and RPH on the performance of desiccant wheel: experimental and numerical investigation

The demand for dry air is steadily rising in air conditioning and storage applications. A desiccant wheel is well recognized for providing continuous and effective dehumidification, with the added advantage of using low-grade thermal energy for the regeneration. In the present study, a desiccant wheel is integrated with a solar air heater that utilizes both-end open evacuated tubes as the heat source. This solar air heater is capable of producing hot air at approximately 122.1°C with an airflow rate of 144 kg/h, thereby enhancing the dehumidification performance of the desiccant wheel. Further, it was observed that with increase in RPH of desiccant wheel from 5 to 20 the dehumidification performance was decreased by 71.5%. At a lower RPH range of 5–10, the desiccant wheel showed its best performance at a velocity ratio of 2, achieving up to 80% dehumidification of the air. On the other hand, at higher RPH it continuously decreases with increase in velocity ratio from 1 to 2.5. The average dehumidification effectiveness and DCOP at 5 RPH, was 0.82 and 0.37, respectively, at a velocity ratio of 2. Further, the cost of dehumidification is observed to be about 0.16 $/kg with CO₂ mitigation of 64.85 tons over the life cycle. Further, a numerical analysis is also conducted with various solid desiccants, revealing that regular density silica gel performs effectively at lower regeneration temperatures, i.e. 70–80°C, whereas activated alumina exhibits superior dehumidification capability at higher regeneration temperatures, i.e. around 100–120°C.