Visualization of the hygroscopic water distribution in an adsorbent bed by neutron radiography

It is important for the design of an adsorption heat exchanger used in an adsorption refrigerator to know the hygroscopic water distribution in the adsorbent bed with cooling or heating, because the adsorption/dehydration process is a complicated phenomenon with heat conduction, vapor diffusion, and vapor flows in the particle bed, and it is a dominant factor on the performance. A neutron radiography method was applied to measure the hygroscopic water distribution in an adsorption bed. In this study, a transient phenomenon in a dehydration process was investigated. Silica gel particles whose component is 99.8% silicone dioxide and diameter is around 0.5 mm are used as an adsorbent, and they are packed in an aluminum cylinder with a 36 mm inner diameter and 100 mm depth. From the radiographs, the transient characteristics of the hygroscopic water distributions were clearly visualized via some image processing methods.