Adsorption Cooling With Multi-Stage Desiccant Processes

For traditional adsorption cooling systems using silica-gel-like desiccant wheels, the moisture is removed from the air and stored in the desiccant wheels. The subsequent reactivation process is to dry the wheel by blowing hot air. The moisture is added to the dried air to take the advantage of evaporative cooling. Currently, the two processes are performed on the different sections of a wheel. However, the temperature of the reactivated part will be higher, and the residual heat will be dissipated into the air-conditioning space. Some researchers have reported to add another section to cool down the regenerative part. Unfortunately, the addition of cooling section decreases the working durations of other two sections. In this study, a novel desiccant-evaporative cooling process is proposed. The wheel is now stationary. Fans and air doors were designed to adjust various air flows to pass through the wheel to perform the dehumidifying, reactivation, and cooling inside the wheel. Most importantly, for each period, the desiccant wheel was used only to dehumidify, reactivate, or cool down. The air to cool the desiccant wheel was released outside, so no residual heat went to the air-conditioning space. The outdoor air was acquired to be heated and reactivate the desiccant wheel. The indoor was used to cool the wheel to achieve better cooling effects. An experimental prototype was designed and established. The air could be directed through the desiccant wheel. A controller was installed. The duration of the dehumidifying, reactivation, and cooling process could be set on the panel. The evaporative cooling process was performed by ten ultrasonic humidifiers. The hot air was from a liquid-to-air heat exchanger, and the hot water can be from a solar heater or any waste heat sources. Optimized sets of period durations were suggested. The criteria to end each process have been proposed for future automation. It is shown that the novel design is able to deliver cooler air. Although the cool air output is currently intermittent, a solution has been figured out and will be improved soon.