Avaliação energética de uma unidade de refrigeração por absorção utilizando brometo de lítio-água (LiBr-H2O)

Abstract

Great part of the consumption of industrial and residential energy is associated with the refrigeration necessity, and indirectly, to the air conditioning. In building not industrials, the cost for climatization can arrive 80% of the costs of electric energy, whereas in the industry, this value can reach up to 40%, for example, the textile industry. The residential sector In Brazil, is the second largest consumer of electricity, due to home cooling system. This motivates the study of refrigeration absorption cycles using the source of solar energy. Although the system of refrigeration and used climatization more is of vapor compression, which uses electric energy to produce the cold, the first system of refrigeration was the absorption cycle (thermal). The study and development of vapor compressors occurred by the easiness of installation of the equipment and the availability of electric energy, thus favoring, the increase of the performance of the cycle of vapor compression and the popularizing of the same. Either for the residential and industrial use or ambient questions, a bigger use of the thermal cycles of refrigeration is essential in the next years. The rational use of the energy resources for the production of the cold requires that other forms of energy, beyond the electric energy, readily are used. This present work aimed to study, design, modeling and simulate the thermo solar system coupled with the absorption refrigeration system using a pair of fluid H2O-LiBr (lithium bromide-water). Through the computer software TRNSYS (Transient System Simulation), version 14.1, it was possible to design and simulate the size of the room to be cooled, the collector area of solar energy, the volume of the tank and the refrigeration absorption cycle as a function of the main termofluid-dynamic parameters. The collector solar energy system has a solar collector, a storage tank, pump and thermal fluid energy carrier, in this case water. The cooling system has five (5) components: evaporator, absorber and heat exchanger located on the low-pressure system, power source and condenser located on the high pressure system. Experimental data as temperature, relative humidity and solar radiation were collected during the period between October and December 2007 at Federal University of Alagoas in Maceió, Brazil. Graphical results show the profiles of average temperature of the environment to be refrigerated with respect to various parameters such as room size, tank volume, solar energy collector area, cooling capacity and minimum temperature refrigeration. The results showed COP variation with time, the auxiliary heat required to absorption cycle as a function of the hot water collector system, among others.