Autor/autori: B. CACIULA, V.POPA , L. COSTIUC

Abstract: This paper investigates the relative performance of a thermally activated environmentally friendly cooling system: a NH3-H2O sorption system. This system can by activated with relatively low heat source temperatures such as those achieved by solar collectors. The study explores the relative thermal performance, i.e. the performance coefficient and refrigeration capacity of the system and a qualitative comparison based on the type of solar collector, i.e. compound parabolic collector. The geographical functioning location of the system was chosen for the city of Bra?ov, Romania for July. Firstly, the solar system collectors was investigated: the efficiency of the solar collectors as a function of the ambient temperament, the solar radiation and heating medium temperature, daily irradiance on a fixed plane, daily irradiance on a 2-axis tracking plane, average daily temperature profile. The absorption system is analyzed. The mathematical model developed is based on the energy and mass conservation equations. The thermodynamic model of ammonia-water binary mixture was used in the calculations. The advantage of this model is given by the high evaluation accuracy of the state points, compared with the common method, with the enthalpy-concentration diagram, where the reading accuracy of the values is relative. The results show an improvement to the design parameters currently used when calculating these types of refrigerating installation. In addition, a minimum number of “requirements” for the refrigerating cycle have been identified in order for this to be able to work within the designed parameters and with acceptable values for the performance coefficients. The thermodynamic model of the ammonia-water binary mixture, once completed, enables different types of absorption thermodynamic cycles to be studied with the purpose of improving their efficiency.

Keywords: absorption, solar refrigeration, sustainable cooling, environmentally friendly techn