engleski

Absorption cooling devices with LiBr / H2O as working media

Nowadays, cooling demand is rapidly increasing in many parts of the world, especially in Mediterranean and moderate climates. Electrically driven compressor chillers are usually used for the refrigeration and space cooling purposes, but their large consummation of electric energy, especially in peak–load periods during the summer, causes some problems in energy systems. This also results with an unwanted increase in consumption of electric energy obtained mainly from fossil fuels. On the other hand, the absorption cooling devices are driven mostly by thermal energy and only a little part of electric energy is used for their operation. Furthermore, solar thermal energy can be used for running the absorption cycles and efficient cooling can be obtained during the periods with largest solar insolation which is in correlation with the system cooling demand. Waste energy from the absorption cycles can be further utilized for the heating of sanitary domestic water. Also, in the periods when there are no needs of cooling, solar thermal energy can be utilized for the space heating of buildings. The market potential for absorption cooling, especially solar cooling, is very large and still under development. These solutions are environmentally friendly because of their lower electricity demand and they also have very low operational costs, which is another advantage. Since the absorption cooling systems are not yet sufficiently recognized in technical practice, an absorption cooling device installed for cooling of a business building in Dubrovnik, Croatia is chosen as the basis for the proposed paper. This paper contains a short historical review of absorption cooling devices, starting from the first experiments revealing that some liquids are capable to absorb aqueous vapour and some other gases all through the mass produced devices that have become forerunners of many modern absorption systems. The aim of the study is to develop the mathematical model of an absorption cooling process in MATLAB and to test this model by calculating thermodynamic properties of binary mixture LiBr/H2O using the constant coefficients given by Dong – Seon Kim and Infante Ferreira. The derived model is used for calculation of absorption cooling process in the working conditions of the installed solar cooling plant in Dubrovnik, Croatia. The technical parameters of the system were collected by using the long distance measurement system. The experimental data are then compared to the data calculated by the model. The comparison confirms that the theoretical model can be applied for this case taking into account slight deviations resulting from the simplifications used in the model (particularly from the idealization in the heat transfer processes).

absorption cooling ; devices ; mathematical model

nije evidentirano