Article about air conditioning

ARTICLE ABOUT AIR CONDITIONING
SUMMARY OF “A novel air conditioning system: Membrane Air Drying and Evaporative Cooling”
Written By: Carlos Andrés Quintero Borrás
Code 200029306 – 5th Semester Mechanical Engineering
Universidad del Norte – Barranquilla

Needs of human body and environmental conditions are not so compatible. In consequence, it is common and necessary to change the conditionsof spaces to be more comfortable. In order to maintain an inhabited space or an industrial installation at a desired temperature and humidity, some air conditioning processes are necessary, and those processes have been widely studied. For example, H.T. El-Dessouky, H.M. Ettouney and W. Bouhamra, from the Department of Chemical Engineering of the College of Engineering and Petroleum of the KuwaitUniversity, proposed a novel system for air conditioning which combines membrane air-drying and an indirect/direct evaporative cooling system.

In this article, there were stated some facts about this novel system. For example, this new combination extends the operating range of the evaporative cooler for small differences of dry and wet bulb temperatures. Also, the investigation of thefeasibility of operating the proposed system for the cooling of ambient air to an outlet temperature of 19°C and a relative humidity of 90% has found that system analysis shows limitations imposed on air cooling by the direct evaporative cooler, the indirect evaporative cooler and the indirect/direct evaporative cooler. For ambient temperatures above 35°C, operation of the ID system requires relativehumidity values below 30%. Energy consumption for various cooling combinations, including mechanical vapor compression, is evaluated by the energy efficiency rating, showing savings of up to 58.9% over the conventional system.

The topic is introduced by explaining about air conditioning in hot and arid environments, as being an essential requirement for support of daily human activities. Forexample, the Middle East and many other countries around the globe have a long summer season with a daily average temperature of 35°C and maximum values in the upper forties. In addition, long spells of humid weather occur during the summer season with relatively lower temperatures, in the mid thirties, and very high relative humidity, with average values above 60% and maximum values close to 90%. Inmany of these countries, the energy used to condition and cool the indoor air ranges from 40 to 70% of the total energy consumption of the country. For this reason, attempts have been made to employ systems that consume lower energy than the stand-alone MVC units. Direct evaporative coolers, known also as single stage evaporative coolers, have a simple design where direct contact is made betweenambient air to be cooled, and water. Contact of air and water results in evaporation of a small amount of water, where the latent heat of evaporation causes simultaneous reductions in the air and water temperatures. Problems related to these cooling units are solved in part by the indirect evaporative cooler and the indirect/direct evaporative cooler.

Conventional mechanical vapor compressionsystems have high power consumption rates and harmful effects on the environment; evaporative coolers consume much lower energy than the MVC system, but their use in a stand-alone mode cannot meet the required cooling load throughout the whole year; combined systems of evaporative coolers and mechanical vapour compression have higher energy consumption rates than the stand-alone evaporativecooling systems. The indirect/direct evaporative cooling systems have better cooling performance than the DEC or IEC units; systems based on air dehumidification with liquid or solid dessicant and evaporative cooling, are not as common or efficient as the mechanical vapor compression units. This is because of operational and design difficulties, which need dessicant refrigeration, elimination or...