Comparative first- and second-law analysis of an absorption cycle

Technical Report · Mon Jul 01 04:00:00 EDT 1985

OSTI ID:5574382

Perez-Blanco, H; Pan, L

Generally, the basis of efficiency calculations and optimization studies of absorption cycles is the first law of thermodynamics. It is often argued that a first-law analysis does not produce all the information needed to optimize the absorption system. According to this line of thought, only an analysis based on the second law of thermodynamics gives the needed information. Assessment of the usefulness of second-law analysis as applied to absorption cycles seems adequate to determine the potential benefits of gathering the additional data for the absorbent-refrigerant combinations currently under consideration. To this end, a comparative first- and second-law analysis of a single-effect, lithium bromide-water absorption cycle is carried out here. An existing computer program and entropy values from the literature are used to analyze the cycle. The effects of temperature approaches in each heat exchanger and external heating/cooling fluid flow rates on the cycle performance are determined. A comparison of the results obtained via first- and second-law analyses reveals that the usefulness of the information depends on the boundaries of the system under consideration. Optimization of the absorption cycle itself, without considering the effect of external heating/cooling fluid flow rates at all, can be accomplished by first-law analysis. However, optimization of not only the cycle but also the external flow rates (i.e., the overall thermal system) is better accomplished by second-law analysis. Another interesting result of this study is that a critical temperature approach for cycle optimization can be found for the generator. In practical terms, this means that improving the heat exchanger in the generator will not always enhance the thermal performance of the cycle. 5 refs., 14 figs., 5 tabs.

• Research Organization: Oak Ridge National Lab., TN (USA)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 5574382
• Report Number(s): ORNL/TM-9595; ON: DE85015066
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140502* -- Solar Energy Conversion-- Thermonic & Thermoelectric conversion
ABSORPTIO
ABSORPTION
ALKALI METAL COMPOUNDS
BROMIDES
BROMINE COMPOUNDS
COEFFICIENT OF PERFORMANCE
DATA
EXPERIMENTAL DATA
HALIDES
HALOGEN COMPOUNDS
HEAT EXCHANGERS
HEAT PUMPS
HYDROGEN COMPOUNDS
INFORMATION
LITHIUM BROMIDES
LITHIUM COMPOUNDS
LITHIUM HALIDES
MATHEMATICAL MODELS
NUMERICAL DATA
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
THERMODYNAMIC PROPERTIES
THERMODYNAMICS
WATER