Modelling of unsteady processes of adsorption refrigeration systems

Abstract

Energy savings on refrigeration systems are highly desired due to the aware ness of limited energy sources in recent years. In this regard, new technologies have been developed in addition to the conventional refrigeration systems, which utilizes fossil fuels as an energy source, in order to utilize renewable energy sources and waste heat. Adsorption refrigeration systems, which are operated by the renewable low-grade thermal energy sources, have drawn attention because of the advantages in aspects of energy saving and being environment friendly. However, adsorption refrigeration sys tems have many problems in terms of long cycle time and low system performance yet to be overcome. In this thesis, adsorption refrigeration systems with non-uniform temperature and non-uniform pressure profile within the adsorbent bed have been investigated by comparing the effect of different operating conditions and working pairs such as sil ica gel-water and activated carbon-methanol on various system parameters in order to analyze the poor heat and mass transfer process within the adsorbent bed. More over, heat and mass recovery operations have been applied to the basic cycle in order to improve system performance by demonstrating their effect on coefficient of perfor mance (COP). The mathematical model has been performed in only radial direction and numerically solved with the help of finite difference method and Newton-Rhapson method by using pre-defined initial and boundary conditions, and discretized partial differential equations implemented in Matlab. The results indicate that the analysis carried out in this thesis shows good agreement with the studies in the literature.