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Dynamic optimization of adsorptive chillers: The “AQSOA™-FAM-Z02 – Water” working pair

Girnik, Ilya S., Aristov, Yuri I.
Energy 2016 v.106 pp. 13-22
adsorbents, adsorption, desorption, heat transfer, temperature
Despite significant progress in commercial ACs (adsorption chillers) achieved for the last thirty years, still there is a much room for their further improvement. This paper addresses the optimization of dynamic performance of ACs utilizing loose grains of a novel adsorbent AQSOA™-FAM-Z02. The dynamic data were measured by a Volumetric Large Temperature Jump method under typical conditions of isobaric ad/desorption stages of real AC cycle. For the first time, the effects of number of the adsorbent layers (N = 2, 4, and 8), grain size (0.2–0.9 mm) and cycle boundary conditions were comprehensively studied. The most notable findings revealed for the water ad/desorption dynamics are: 1) the initial part of all kinetic curves is exponential and can be described by a single characteristic time τ; 2) at equal values of the ratio (S/m)=(heat transfer surface)/(adsorbent mass), the dynamic curves are very close regardless the adsorbent grain size R (the “grain size insensitive” regime is observed at 0.44 m²/kg ≤ (S/m) ≤ 1.75 m²/kg); 3) the maximal specific cooling power is a linear function of the (S/m)-ratio. Appropriate recommendations on improving the AC cycle dynamics which concern the optimal conversion degree, grain size and (S/m)-ratio are made.