Reducing Energy Consumption Of Air-Conditioners In Warm-Humid Climates Through Desiccant Cooling - A Cfd Study

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ABSTRACT The ambient temperature and relative humidity in hot-humid climates, particularly in most countries in sub-Saharan Africa, can get as high as 41 °C and 84%, respectively. For indoor thermal comfort for people, temperature of 20–25 °C and relative humidity of 50–55% should be maintained. Air-conditioners that operate with vapour compression cycle are used to maintain such conditions. In conventional Vapour Compression Systems (VCS), inlet air is cooled below its dew point for dehumidification and then reheated again to obtain air flow with desired temperature and humidity. This process of dehumidification and reheating is inefficient and leads to high consumption of energy. In Desiccant Cooling Systems, dehumidification of air is done by utilizing desiccant material to get desirable humidity and then the dry air is cooled by evaporation method or cooling coils down to suitable temperature. The process of using desiccant to control the air humidity before the air-conditioning process makes the system more energy efficient. In this work, a CFD study has been conducted to ascertain how desiccant can be used to reduce the relative humidity of air prior to the air-conditioning process. The CFD simulations were conducted using TRNSYS software with input data from the Typical Metrological Year (TMY) data for Kumasi. The results show that the desiccant system is able to reduce the cooling load of a selected inefficient VCS in an office in Kumasi by as much as 65%. In addition, analysis in this study has shown that there is potential electricity savings of 2406 kWh/year with the desiccant cooling system over the conventional VCS.
A Thesis submitted to the School of Graduate studies, Kwame Nkrumah University of science and technology, Kumasi, Ghana In partial fulfillment of the requirements for the degree of MASTER OF PHILSOPHY IN MECHANICAL ENGINEERING