Activated carbon fiber cloth and CaCl2 composite sorbents for a water vapor sorption cooling system

• Activated carbon fiber cloth (ACFC) and CaCl2 composite sorbents were prepared.
• Formation mechanism of the composite sorbents during the impregnating was revealed.
• Ca2+ adsorption by the surface groups can be ignored for the composite preparation.
• CaCl2 concentration in the pores of the ACFC can be described by D–R equation.
• The composite is promising for sorption cooling system.

In this work, we investigated activated carbon fiber cloth (ACFC) and CaCl2 composite sorbent (CS) prepared using impregnation method. Formation mechanism of the composite was investigated. During the impregnation process, a solution of CaCl2 is concentrated inside the pores of the ACFC. The solution concentration process is described using the Polanyi potential theory and the Dubinin–Radushkevich equation while ignoring Ca2+ adsorption by the surface functional groups. If the CaCl2 content of the CS is less than 38.2%, all the CaCl2 locates inside the pores of the ACFC. The water sorption performances of the CS of different CaCl2 contents were measured using an ASAP2020M Accelerated Surface Area and Porosimetry analyzer. The CSs with a CaCl2 content of 15.2 and 22.8% exhibit a greater amount of absorbed water than the equivalent CaCl2. This is because the CaCl2 dispersed inside within pores exhibits a lower hydration pressure than the bulk CaCl2, and the ACFC contributes to the amount of water that is absorbed. However, it is likely that the hydration pressure of the dispersed CaCl2 in the CS containing the maximum possible amount of CaCl2 does not change. Water sorption in this kind of CS can reach as high as 90% of the equilibrium water sorption amount within 2 min. The coefficient of performance for the air conditioning cycles calculated from the isosters of the CS containing the maximum CaCl2 content may reach 0.7, which is considered promising for sorption cooling.