Abstract
The Kalina flash cycle (KFC) is a novel, recently proposed modification of the Kalina cycle (KC) equipped with a flash vessel. This study performs a comparative analysis of the thermodynamic performance of KC and KFC utilizing low-grade heat sources. How separator pressure, flash pressure, and ammonia mass fraction affect the system performance is systematically and parametrically investigated. Dependences of net power and cycle efficiencies on these parameters as well as the mass flow rate, heat transfer rate and power production at the cycle components are analyzed. For a given set of separator pressure and ammonia mass fraction, there exists an optimum flash pressure making exergy efficiency locally maximal. For these pressures, which are higher for higher separator pressure and lower ammonia mass fraction, KFC shows better performance than KC both in net power and cycle efficiencies. At higher ammonia mass fraction, however, the difference is smaller. While the maximum power production increases with separator pressure, the dependence is quite weak for the maximum values of both efficiencies.
Highlights
The Kalina cycle (KC) is a novel power cycle proposed in the early 1980s by Kalina [1] which replaces water of the steam cycle by an ammonia-water mixture and is equipped with a vapor-liquid separator
In order to compare the thermodynamic performance of the Kalina flash cycle (KFC) with that of the Kalina cycle (KC), the performance of KFC is analyzed first
By taking ammonia mass fraction and separator pressure for both cycles and flash pressure for KFC as key parameters, a parametric study was systematically performed on the effects of these parameters on the cycle performance
Summary
The Kalina cycle (KC) is a novel power cycle proposed in the early 1980s by Kalina [1] which replaces water of the steam cycle by an ammonia-water mixture and is equipped with a vapor-liquid separator. Sun et al [14,15] carried out an energy-exergy analysis for a solar boosted KC with an auxiliary superheater to utilize low-grade heat sources They reported a parametric optimization result for a pilot system that the generated power, exergy and energy efficiencies reaching up to 491 kW, 35.6%, and 6.48%, respectively. Proposed a KC integrated with thermoelectric generators to directly convert heat into electricity They reported an enhancement of 7.3% in net power with efficiencies comparable to the conventional. This study carries out a comparative analysis of the thermodynamic performance of KC and KFC utilizing low-grade heat sources. It is systematically investigated how flash pressure and other system parameters affect their thermodynamic performance. The dependences of mass flow rates, heat transfer rates and power production at the appropriate components and the dependences of net power and efficiencies of the systems on these parameters are analyzed
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