Composite sorbent of methanol “LiCl in mesoporous silica gel” for adsorption cooling: Dynamic optimization

A novel composite sorbent of methanol “LiCl in mesoporous silica gel” has recently been proposed for AC (adsorption cooling). Its testing in a lab-scale adsorption chiller resulted in the specific cooling power of 210–290 W/kg and the cooling COP of 0.32–0.4. Although these values are rather encouraging, a room for their enhancement still exists. The aim of this paper was a dynamic optimization of the composite performance in AC cycles. Dynamics of methanol sorption on loose grains of the LiCl/silica composites was studied by a Large Temperature Jump method under typical conditions of AC cycle. Effects of number of the sorbent layers, salt content, grain size and cycle boundary temperatures were studied. Physico-chemical processes in the three-phase system (salt, solution, vapor) were shown to be quite complex and can strongly affect the dynamics of methanol ad-/desorption. Several obstacles which can retard the sorption were analyzed. Appropriate recommendations on improving the cycle dynamics, which concern optimal conversion degree, salt content and relative durations of ad- and desorption phases, were made.

Research highlights
► Dynamic optimization of methanol sorption on composite LiCl/silica gel for adsorption cooling.
► Effects of number of the sorbent layers, salt content, grain size and cycle boundary temperatures.
► Interactions in three-phase system (vapor, salt and its solution) affect adsorption dynamics.
► Sorption rate depends on driving force for chemical reaction and driving force for heat transfer.
► Appropriate recommendations on improving the cycle dynamics are made.