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Absorption systems offer an alternative way to substitute energy economically in mechanical compression systems in the field of refrigeration and air conditioning. The aim of this article is to investigate the transient performance of a single effect absorption chiller using the pair LiBr/H 2 O when the overall heat transfer coefficients are varied in time by updating the thermo-physical properties and convective coefficients. A thermodynamic model was developed based on conserving mass and energy and considers, so as to determine the overall heat transfer coefficients of the heat exchangers of a chiller and the correlations of the convective coefficients of the processes of refrigeration by absorption (desorption, absorption, condensation and evaporation). This model when tested for real operating conditions and considering the overall coefficients of heat transfer were constant throughout the process showed relative errors were less than 15% in the chilled water circuit and under 2% in cold water. This difference drops significantly when the variable overall coefficients are considered throughout the process, these errors being approximately 5% and 0.3%, there being a percentage fall in all water circuits. [ABSTRACT FROM AUTHOR]

This paper shows a thermodynamic cogeneration model (single-effect LiBr/H 2 O absorption chiller coupled to a 30 kW microturbine, a cooling tower and a heat exchanger) and analyzes energetic and exergetic behavior of the system. A computational algorithm was developed on the EES-32 platform to evaluate the influence of the main operating parameters of the cogeneration system. The effect of parameters such as hot water temperature, the microturbine load, the ambient temperature, etc. on the cooling capacity and the COP (Coefficient of Performance) of the chiller are analyzed. The balance equations are based on the principles of conservation of energy, mass and species. The total exergy of the working fluids was calculated taking into account the physical and chemical characteristics. In the cogeneration system, the greatest irreversibility was found in the microturbine with 52.88 kW and the least in the absorption chiller with 1.78 kW. The analysis was performed by varying the load of microturbine and its influence on the COP and the cooling capacity. The COP values are based on the first and second law of thermodynamics. Due to the load variation of the microturbine, and its influence on inlet and outlet temperatures of the water, the COP values were obtained 0.74 and 0.24, respectively. Finally the overall energy and exergy efficiencies of cogeneration was determined, these values were about 50% and 26%, respectively. [ABSTRACT FROM AUTHOR]