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This paper presents the exergy analysis of a single effect water-LiBr adiabatic absorption facility. A comparison to diabatic (isothermal) absorption systems was carried out, under varying operating parameters in terms of the coefficient of performance and exergy efficiency. The effect of generator, absorption, and evaporator temperatures on these parameters was determined as well as the inclusion of the exergy analysis for individual components. The results obtained allowed for the identification of the parameters that influence the performance of the adiabatic absorption system: where the recirculation ratio RR emerged as an important parameter showing that with increasing RR values the exergy efficiency and coefficient of performance improved and that the irreversibility of absorber and generator was more sensible to RR variations than to other components. Two recirculation configurations were analyzed, and it was verified that there were not significant differences in performance when the presented configuration was modified. The results also showed that the coefficient of performance could be up to 20% higher with adiabatic absorbers than with those systems operating with diabatic absorbers [ABSTRACT FROM AUTHOR]

Abstract: Various researchers have developed models of conventional H2O–LiBr absorption machines with the aim of predicting their performance. In this paper, the methodology of characteristic equations developed by is applied. This model is able to represent the capacity of single effect absorption chillers and heat pumps by means of simple algebraic equations. An extended characteristic equation based on a characteristic temperature difference has been obtained, considering the facility features. As a result, it is concluded that for adiabatic absorbers a subcooling temperature must be specified. The effect of evaporator overflow has been characterized. Its influence on cooling capacity has been included in the extended characteristic equation. Taking into account the particular design and operation features, a good agreement between experimental performance data and those obtained through the extended characteristic equation has been achieved at off-design operation. This allows its use for simulation and control purposes. [Copyright &y& Elsevier]

Abstract: A facility for experimental evaluation of innovative components forming part of a single effect LiBr–H2O adiabatic absorption chiller is described. Plate heat exchangers have been incorporated in the design. Two adiabatic absorber configurations, droplets and liquid sheets, were designed and tested and its performances parameters were experimentally determined. Evaporator limitations have been identified and included in the analysis. Liquid accumulation leads to overflow of refrigerant out of the evaporators. Some general observations, regarding particular operating conditions, are reported. The absorber performance has been characterized in terms of heat and mass transfer through the heat conductance and the effectiveness. The influence of the recirculation ratio is presented for both cases. The liquid sheet configuration has shown better evaluation parameters than droplets configuration. A significant reduction in the absorber size (up to 50%) as compared to using droplets is possible. [Copyright &y& Elsevier]

This paper reports the experimental results of a single effect absorption cooling system of 3 kW of nominal cooling capacity operating with ammonia–lithium nitrate solution. The system was designed and built in the Instituto de Energías Renovables of the Universidad Nacional Autónoma de México and can be used for food conservation or air conditioning. The absorber and generator are falling film heat exchangers. The condenser, evaporator and solution heat exchanger are compact plate heat exchangers. The heat was supplied to the generator at temperatures between 85 °C and 105 °C, while the cooling water temperatures to remove the heat produced during the condensation and absorption varied between 18 °C and 36 °C. The results showed that the system can produce up to 2.7 kW of cooling capacity at heating water temperatures of 95 °C and can achieve evaporator temperatures as low as 1 °C. The experimental coefficients of performance varied between 0.45 and 0.70. Because of the developed system do not need a rectifier and reasonable good coefficients of performance were achieved, the developed system seems to be a good alternative to be used for food conservation or air conditioning. [ABSTRACT FROM AUTHOR]