Dramatic effect of residual gas on dynamics of isobaric adsorption stage of an adsorptive chiller

• The effect of non-adsorbable gases on dynamics of an adsorptive chiller is studied.
• The tests were performed on representative fragments of real heat exchangers.
• The adsorption rate is extremely sensitive to traces of residual air/hydrogen.
• Minimal amount of air necessary to significantly slow down the adsorption is found.

This paper reports an experimental study aimed to elucidate the effect of non-adsorbable gases (air and hydrogen) on dynamics of isobaric adsorption stage of an adsorptive chiller (AC) cycle. This is the first study performed on real small scale adsorbers, based on commercial heat exchangers (HExs) filled with loose grains of the adsorbent AQSOA™-FAM-Z02. The adsorption dynamics was studied by a gravimetric large temperature jump method under conditions of typical AC cycle. Three notable observations are described in the paper: (1) at any gas pressure Pgas, the experimental uptake curves are exponential; (2) the adsorption rate is extremely sensitive to traces of residual air and depends on the HEx geometry and the nature of residual gas; (3) the effect of hydrogen is less dramatic as compared with air. The minimal amount of residual air necessary to form the blocking air-rich layer is evaluated by developing a one-dimensional stationary model of the vapour adsorption in the presence of gas. This amount is found to be highly sensitive to the total vapour pressure and the HEx mass transfer surface area. Practical recommendations on avoiding/dumping the effect of residual gas are made.