SUMMARYIn the present study, the first and second law of thermodynamics have been used to analyze in detail the performance of a double absorption (lift) heat transformer operating with the water-lithium bromide mixture. A mathematical model was developed to estimate the coefficient of performance (COP), the exergy coefficient of performance (ECOP), the total exergy destruction in the system (C TD ) and the exergy destruction (C D ) in each one of the main components, as a function of the system temperatures, the efficiency of the economizer (EF EC ), the gross temperature lift and flow ratio (FR). The results showed that the generator is the component with the highest irreversibilities or exergy destruction contributing to about 40% of the total exergy destruction in the whole system, reason why this component should be carefully designed and optimized. The results also showed that the COP and ECOP increase with increase in the generator, the evaporator and the absorber-evaporator temperatures and decrease with the absorber and condenser temperatures. Finally, it was observed that the COP and ECOP are very dependent of the FR and the economizer efficiency (EF EC ) values. Also the optimum operating region of the analyzed system is shown in the present study.

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SUMMARYThe first and second law of thermodynamics have been used to analyze the performance of an experimental single-stage heat transformer operating with the water/lithium bromide mixture. Enthalpy coefficients of performance (COP), external coefficients of performance (COP EXT ), exergy coefficient of performance (ECOP), exergy destruction or irreversibility in the system and components (I) and the improvement potential (Pot) have been calculated against the gross temperature lift and the main operating temperatures of the system. The results showed that the highest COP, COP EXT and ECOP values are obtained at the highest solution concentrations meanwhile the Pot and the I of the cycle remain almost constant against these parameters. Also it was shown that the COP, COP EXT and ECOP decrease with an increase with the absorber temperature, meanwhile the Pot and the I increase. Moreover, it was observed that in all the cases independently of the operating temperatures of the system, the absorber accounts with most of the half of the total irreversibility in the system. Finally, it was shown that the improvement potential is considerable for the system.

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