Thermodynamic study of isosteric heat at zero coverage : applications to adsorption cooling and desalination

Abstract

The production of cooling and drinkable water represents major and essential needs for the mankind. Vapor compression cooling and desalination systems are mainly driven by electricity, produced by burning fossil fuels, which contributes to the global warming (GW) because of the encountered direct CO 2-emissions. The refrigerants used in vapor compression systems possess high global warming potential (GWP), resulting in an indirect contribution to the GW and, consequently, to the severe consequences on the worldwide climate. Recovering the waste heat generated upon burning fossil fuels to provide both cooling and fresh water demands through the application of adsorption assisted cooling and desalination cycle may remarkably contribute in mitigating the bad consequences of the GW. At present, the bulky size of adsorption chiller and desalination systems obstructs its practical application. The size of an adsorption bed depends on the quality of the porous adsorbents. Therefore, the present thesis aims to develop a thermodynamic framework for calculating the interaction potentials between the adsorbate and the adsorbent pore structures, from which the isosteric heat at zero coverage is formulated as a function of pore width and volume. The proposed modelling provides necessary information for the design of adsorbent materials. The proposed interaction potential model includes the Lennard Jones (LJ) Potential with the inclusion of electrostatic and induction potential. The model is first applied to the graphite surface, in which the electrostatic and induction potentials are obtained to be very small compared to the LJ potential. The maximum isosteric heat is found in the super micro-pore regions. On the other hand, the Reverse Monte Carlo (RMC) and molecular dynamics methods are applied to understand the silica structure for water adsorption. For water interaction with silica gel, the electrostatic interaction is found to be high. For water adsorption on CHA and AFI 4.4 Summary of Chapter 4 ..