Design and Simulation of Solar Adsorption Cooling System for Residential Applications
Amati, Dan Aggrey
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Many Ugandans might have experienced the increased temperatures in their living rooms of late. The humidity of air for instance (average 80.3%) is the maximum reached in a year at Entebbe, Uganda. The average annual temperature in Uganda is recorded to be 26oC. This has led to increased purchase of cooling devices as such increase in the energy demand to run these devices. It is reported the electricity demand has also been increasing at 10% per annum of which residential portion is 24.24% just after industrial sector. This electricity is utilized by technologies with more harmful effects to meet the cooling demand in most instances, these dire effects will be experienced later. It is only prudent attention needs to gradually shift to the design of technologies that no longer aid this situation. Solar adsorption cooling systems is one of these technologies. It is environmentally sound, there are no moving parts and as such less maintained. Methanol and activated carbon are used as working pairs. Recent developments in this technology have experienced setbacks in performance as compared to the available options hence their less demand. Studies will always continue to improve these systems because they are the future. To analyze such systems in our environment specifically Makerere University, models were generated based on the geographical location and climatic conditions herein. These were used to produce results of a simulation using MATLAB and Engineering Equation Solver (EES). This formed the basis of analysis. The major aim of this theoretical endeavor was to study the effects of temperature variations on the most important component, the adsorber under the prevailing climatic data obtained on Makerere University. This is then used to suggest improvements on the components for better performance. This study showed that for a significant amount of methanol to be desorbed from the activated carbon in a cooling system with evaporator temperature ranging from 0 to 20oC and condenser temperatures ranging from 30 to 40oC, a temperature of at least 90oC is required by the adsorbent bed. The maximum COP produced during desorption is 0.2578. The temperature 90oC is achievable under these weather conditions considering the design of the bed. This goes to show that solar adsorption cooling system can be an effective, practicable and ecofriendly for Makerere with abundant sunshine. Suggestions were further made to improve this performance through heat transfer enhancements in the adsorber to improve on the temperature distribution in the bed. This is for faster desorption of refrigerant.