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)

• Published in: Applied thermal engineering Vol. 31; no. 16; pp. 3526 - 3532
• Main Authors: Rivera, W., Martínez, H., Cerezo, J., Romero, R.J., Cardoso, M.J.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-11-2011; Elsevier
• Subjects: Absorption heat transformers; Additives; Applied sciences; Bromides; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Exergy; Generators; Heat transfer; Heat transformers; Law; Lithium; Mathematical analysis; Operating temperature; Theoretical studies. Data and constants. Metering; Thermal engineering; Water/lithium bromide; Additives; Exergy; Water/lithium bromide; Absorption heat transformers; Energy analysis; Thermodynamics; Additive; Exergy analysis; Enthalpy; Lithium bromide; Performance; Heat transfer
• ISSN: 1359-4311
• DOI: 10.1016/j.applthermaleng.2011.07.006

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 °C and 88 °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.
► An exergy analysis has been used to analyze an experimental heat transformer. ► The system operated with single water/lithium bromide and then adding two additives. ► The additives were 1-octanol and 2-ethyl-1-hexanol. ► The 2-ethyl-1-hexanol additive reduced the system irreversibilities. ► The highest coefficients of performance were obtained with the 2-ethyl-1-hexanol additive.