Exergy analysis of an experimental single-stage heat transformer operating with single water/lithium bromide and using additives (1-octanol and 2-ethyl-1-hexanol)

Second law of Thermodynamics has been used to analyze the performance of an experimental single-stage heat transformer operating with the water/lithium bromide as single working pair and subsequently, using 1-octanol and 2-ethyl-1-hexanol as additives. Additives have been used in order to increase the heat transfer in the absorber and generator decreasing their irreversibilities. The enthalpy-based coefficients of performance (COP), external coefficients of performance (COP(EXT)), exergy-based coefficients of performance (ECOP) and the irreversibilities of the equipment components were calculated for the main operating temperatures of the system. The results showed that for absorber temperatures between 84 degrees C and 88 degrees C the highest COP, COP(EXT), and ECOP are obtained with the use of the 2-ethyl-1-hexanol (400 parts per million) additive, reaching values up to 0.49, 0.40 and 0.43, respectively. The lowest coefficients of performance and highest irreversibilities were obtained by using the single water/lithium bromide mixture. Analysing the irreversibilities in each one of the main components of the system, it was found that 2-ethyl-1-hexanol decreases considerably the irreversibility in the absorber then increasing the efficiency of this component and hence of the entire equipment. (C) 2011 Elsevier Ltd. All rights reserved.