Adsorption cooling cycle with / without heat and mass recovery enhancements

Abstract

In this thesis study an adsorption cooling system containing two adsorption beds that operate conversely, an evaporator and a gas cooler is modeled. The model is constructed based on heat and mass transfer equations. The temperature in the bed is considered uniform and the numerical model is developed with time dependent Euler’s explicit numerical solution method. The cycle time is divided into phases where the adsorption beds operate at converse processes. The temperature and concentration variation at each phase is obtained and the performance of the cooling system is stated in terms of SCP and COP. For simple cycle, performances of two different adsorption pairs (MAXSORB-III/CO2 and ACF-20/CO2) are investigated. MAXSORB-III is chosen to be operated in recovery cycles since it has better adsorption performance than ACF-20 according to simple bed analyzes. Heat transfer enhancement is included into model by adding heat recovery phases between sorption and isosteric processes. The duration of heat recovery process is determined by comparing the influence on performance indicators COP and SCP. Heat recovery enhances the performance in terms of COP but does not have any influence on SCP. To improve SCP, mass recovery process is involved before the heat recovery process until the bed pressures are equalized. It is shown that the amount of mass that can be recovered, is dependent on evaporation temperature at constant desorption pressure. Simple, heat recovery and mass & heat recovery cycle pressure-temperature-concentration diagrams obtained to show the effect of enhancements on temperature and concentration at each process. Finally the effect of hot source temperature and evaporation temperature and adsorbent mass amount is shown at each type of cycles.