INTRODUCTION In the last few decades@ due to the increasing level of pollution worldwide and the cost of energy@ the search for maximum exploitation of the available energy has lead to the development and use of cogeneration or trigeneration systems. Heating@ ventilation@ air-conditioning@ and refrigeration systems (HVAC-R) play a major role in modern society energy consumption. These systems are mostly based on the vapor compression cycle@ due to high efficiency@ but the vapor compression cycle needs work input@ and high energy consumption is still observed@ therefore research efforts have been made to develop intelligent refrigeration systems in order to reduce energy consumption (Vargas and Parise 1995; Buzelin et al. 2005). Hence@ alternative HVAC-R systems have been the subject of much recent scientific research. Among these systems@ absorption refrigeration is receiving great attention since it may produce energy@ heat and cold@ using@ as energy source@ waste heat from industrial processes or@ for instance@ exhaust gases in automobiles (Temir and Bilge 2004). The major companies working on this area focus on large capacity absorption systems@ i.e. above 100 TR. However@ since most refrigeration and air-cooling units are of small capacity and operate based on vapor compression cycle systems@ there is still a vast field in which absorption systems could be employed. An absorption system also allows the direct use of primary energy@ particularly solar energy and natural gas@ for refrigeration purposes (Ezzine et al. 2004). Although this system is less costly and simpler than vapor compression systems@ its comparatively low coefficient of performance has limited its use to few and specific applications. Nevertheless@ the absorption refrigeration system may reach a refrigeration capacity higher than that of a vapor compression system when energy sources such as waste (residual) heat from industrial processes@ gas or vapor turbines@ sunlight or biomass are used instead of electricity (Adewusi and Zubair 2004). The performance of absorption systems is dependent on an adequate choice of the refrigerant/sorbent working pair@ and ammonia-water has been receiving great attention since these fluids do not contribute to the greenhouse effect (Bruno et al. 1999; Lazzarin et al. 1996). The technical literature is rich in publications on the absorption refrigeration field. Particularly@ Abreu (1999) and Villela and Silveira (2005) used as heat source for absorption systems@ the combustion of liquid petroleum gas (LPG) and biogas@ respectively@ studying the design and performing a thermoeconomic analysis of the analyzed systems. Other studies focused on the exergy analysis of absorption refrigeration systems@ including Sedighi et al. (2007)@ Hasabnis and Bhagwat (2007)@ Khaliq and Kumar (2007)@ Arivazhagan et al. (2006)@ and Sencan et al. (2005). Simulation and optimization studies have also been published analyzing the absorption refrigeration system in isolation (Vargas et al. 1996; Vargas et al. 2000a; Vargas et al. 2001). However@ the exergy analysis and optimization of an absorption refrigerator to produce cooling and heating@ based on a theoretical-experimental model@ could not be found in the open literature. The aim of this work is two-fold: i) to formulate theoretically the absorption system heat transfer interactions using a simplified mathematical model for the energy and exergy analysis of an existing LPG (gas fired) driven absorption refrigeration unit@ and ii) based on experimental measurements@ to characterize system pull-down times and to carry out an energetic and exergetic optimization for maximum thermodynamic performance of the system@ i.e.@ minimum energy consumption.