Effect of Residual Gas on Water Adsorption Dynamics Under Typical Conditions of an Adsorption Chiller

In this article the effect of a non-adsorbable gas (air) on kinetics of water adsorption on loose grains was studied for three adsorbents promising for adsorption chilling: SWS-1L (silica KSK modified by calcium chloride), silica Fuji type RD, and FAM-Z02. The experimental conditions were fixed similar to real operating conditions during an isobaric adsorption stage of the basic cycle of an adsorption chiller (AC). Reduction of the adsorption rate was revealed even at a partial pressure of residual air as low as 0.06 mbar. Dependence of the characteristic adsorption time on air partial pressure was found to be linear for partial pressures greater than 0.4 mbar, with the slope depending on the adsorbent nature. Desorption stage was less affected by the residual air. Specific power released in an AC evaporator during the adsorption process was estimated as a function of the partial pressure of residual air, and recommendations how to improve cooling performance are made.

[1]  Michael A. Lambert,et al.  Design of solar powered adsorption heat pump with ice storage , 2007 .

[2]  D. A. Frank-Kamenet︠s︡kiĭ.  Diffusion and heat transfer in chemical kinetics , 1969 .

[3]  G. Cacciola,et al.  A family of new working materials for solid sorption air conditioning systems , 2002 .

[4]  Kim Choon Ng,et al.  Adsorption Characteristics of Silica Gel + Water Systems , 2002 .

[5]  Yuri I. Aristov,et al.  New composite sorbents of water and ammonia for chemical and adsorption heat pumps , 2006 .

[6]  Yuri I. Aristov,et al.  Kinetics of water adsorption on loose grains of SWS-1L under isobaric stages of adsorption heat pumps: The effect of residual air , 2008 .

[7]  A. Freni,et al.  Selective water sorbent for solid sorption chiller: experimental results and modelling , 2004 .

[8]  Kim Choon Ng,et al.  Investigation on the isotherm of silica gel+water systems , 2004 .

[9]  K. Ng,et al.  Experimental investigation of the silica gel–water adsorption isotherm characteristics , 2001 .

[10]  Giovanni Restuccia,et al.  Selective water sorbents for multiple applications, 1. CaCl2 confined in mesopores of silica gel: Sorption properties , 1996 .

[11]  A. Freni,et al.  Kinetics of water sorption on SWS-1L (calcium chloride confined to mesoporous silica gel): Influence of grain size and temperature , 2006 .

[12]  B. Dawoud,et al.  A new methodology of studying the dynamics of water sorption/desorption under real operating conditions of adsorption heat pumps: Experiment , 2008 .

[13]  J. Rawlings.  Diffusion and heat transfer , 2011 .

[14]  Takao Kashiwagi,et al.  Computer simulation of a silica gel-water adsorption refrigeration cycle - the influence of operating conditions on cooling output and COP , 1995 .

[15]  Hiroyuki Kakiuchi,et al.  Water vapor adsorbent FAM-Z02 and its applicability to adsorption heat pump , 2005 .

[16]  Yuri I. Aristov,et al.  Kinetics of water adsorption on silica Fuji Davison RD , 2006 .