scholarly journals Exergy Analysis of Kalina and Kalina Flash Cycles Driven by Renewable Energy

2020 ◽  
Vol 10 (5) ◽  
pp. 1813
Author(s):  
Kyoung Hoon Kim ◽  
Hyung Jong Ko ◽  
Chul Ho Han
Keyword(s):  
Exergy Analysis ◽  
Power Production ◽  
Ammonia Concentration ◽  
Exergy Efficiency ◽  
Low Grade ◽  
Heat Sources ◽  
Exergy Destruction ◽  
Kalina Cycle ◽  
Low Grade Heat ◽  
Exergy Performance

The Kalina cycle (KC) has been recognized as one of the most efficient conversion systems of low-grade heat sources. The Kalina flash cycle (KFC) is a recently proposed novel cycle which is equipped with an additional flash process to the KC. In this study, the exergy performance of KC and KFC driven by a low-grade heat source are investigated comparatively. The dependence of the exergy destruction at each component as well as the system’s exergy efficiency on ammonia concentration, separator pressure and, additionally, flash pressure for KFC, are systematically investigated. Results showed that KFC can be optimized with respect to flash pressure on the base of exergy efficiency, and the component where largest exergy destruction occurs varies for different separator pressure and ammonia fraction in both systems. It is also shown that the maxima of net power production and exergy efficiency in KFC with optimal flash pressure are superior to those in KC.

scholarly journals Comparative Thermodynamic Analysis of Kalina and Kalina Flash Cycles for Utilizing Low-Grade Heat Sources

Energies ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 3311 ◽  
Author(s):  
Kyoung Kim ◽  
Chul Han ◽  
Hyung Ko
Keyword(s):  
Mass Fraction ◽  
Power Production ◽  
Low Grade ◽  
Heat Sources ◽  
Kalina Cycle ◽  
Thermodynamic Performance ◽  
Locally Maximal ◽  
The Difference ◽  
Proposed Modification ◽  
Low Grade Heat

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.

Low-Grade Heat Source Utilization by Carbon Dioxide Transcritical Power Cycle

2007 ◽  
Author(s):  
Yang Chen ◽  
Wimolsiri Pridasawas ◽  
Per Lundqvist
Keyword(s):  
Carbon Dioxide ◽  
Dynamic Performance ◽  
Average Power ◽  
Power Production ◽  
Low Grade ◽  
Heat Sources ◽  
Climate Conditions ◽  
Power Cycle ◽  
Transcritical Carbon Dioxide ◽  
Low Grade Heat

One way to reduce the fossil fuel consumption and mitigate environmental impact is to utilize low-grade heat sources for power production. In this paper, a transcritical carbon dioxide power cycle is analyzed for its potential in utilizing the low-grade heat sources. Solar thermal is selected as a representative of low-grade heat sources. TRNSYS 16 and Engineering Equation Solver (EES) are employed using co-solving technique to analyze the dynamic performance of the proposed system. Both daily performance and annual performance of the proposed system under Swedish climate conditions are simulated. The simulation results show that the proposed system can achieve 8% average thermal efficiency and consequently 2.43 kW average power production during the system working period on a randomly selected summer day with a 30 m2 solar collector. Over the whole year, the maximum daily power production is about 17 kWh and the maximum monthly power production is about 185 kWh.

scholarly journals Analysis and Optimization of Exergy Flows inside a Transcritical CO2 Ejector for Refrigeration, Air Conditioning and Heat Pump Cycles

Energies ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1686 ◽  
Author(s):  
Sahar Taslimi Taleghani ◽  
Mikhail Sorin ◽  
Sébastien Poncet
Keyword(s):  
Critical Point ◽  
Exergy Analysis ◽  
Exergy Efficiency ◽  
Performance Criteria ◽  
Exergy Destruction ◽  
Two Phase ◽  
1D Model ◽  
Ejector System ◽  
Exergy Performance ◽  
The Impact

In this study, the exergy analysis of a CO2 (R744) two-phase ejector was performed using a 1D model for both single and double choking conditions. The impact of the back pressure on the exergy destruction and exergy efficiencies was presented to evaluate the exergy performance under different working conditions. The results of two exergy performance criteria (transiting exergy efficiency and Grassmann exergy efficiency) were compared for three modes of an ejector functioning: Double choking, single choking and at the critical point. The behavior of three thermodynamic metrics: Exergy produced, exergy consumed and exergy destruction were evaluated. An important result concerning the ejector’s design was the presence of a maximum value of transiting exergy efficiency around the critical point. The impact of the gas cooler and evaporator pressure variations on the different types of exergy, the irreversibilities and the ejector global performance were investigated for a transcritical CO2 ejector system. It was also shown that the transiting exergy flow had an important effect on the exergy analysis of the system and the Grassmann exergy efficiency was not an appropriate criterion to evaluate a transcritical CO2 ejector performance.

scholarly journals Influence of evaporating rate on two-phase expansion in the piston expander with cyclone separator

2020 ◽  
Vol 24 (3 Part B) ◽  
pp. 2077-2088 ◽  
Author(s):  
Weifeng Wu ◽  
Qi Wang ◽  
Zhao Zhang ◽  
Zhijun Wu ◽  
Xiaotian Yang ◽  
...  
Keyword(s):  
Low Grade ◽  
Cyclone Separator ◽  
Expansion Process ◽  
Two Phase ◽  
Kalina Cycle ◽  
Thermodynamic Cycles ◽  
Heat Utilization ◽  
Inlet Stream ◽  
Organic Rankine Cycles ◽  
Low Grade Heat

The trilateral flash cycle shows a greater potentiality in moderate to low grade heat utilization systems due to its potentiality of obtaining high exergy efficiency, compared to the conventional thermodynamic cycles such as the organic Rankine cycles and the Kalina cycle. The main difference between the trilateral flash cycle and the conventional thermodynamic cycles is that the superheated vapor expansion process is replaced by the two-phase expansion process. The two-phase expansion process actually consists of a flashing of the inlet stream into a vapor and a liquid phase. Most simulations assume an equilibrium model with an instantaneous flashing. Yet, the experiments of pool flashing indicate that there is a flash evaporating rate. The mechanism of this process still remains unclear. In this paper, the flash evaporating rate is introduced into the model of the two-phase expansion process in the reciprocating expander with a cyclone separator. As such, the obtained results reveal the influence of evaporating rate on the efficiency of the two-phase expander.

Exergy Analysis of a Combined Power and Refrigeration Thermodynamic Cycle Driven by a Solar Heat Source

2003 ◽  
Vol 125 (1) ◽  
pp. 55-60 ◽  
Author(s):  
Afif Akel Hasan ◽  
D. Y. Goswami
Keyword(s):  
Heat Source ◽  
Exergy Analysis ◽  
Thermodynamic Cycle ◽  
Exergy Efficiency ◽  
Operating Conditions ◽  
Optimum Operating ◽  
Water Mixture ◽  
Exergy Destruction ◽  
Ammonia Water ◽  
Solar Heat

Exergy thermodynamics is employed to analyze a binary ammonia water mixture thermodynamic cycle that produces both power and refrigeration. The analysis includes exergy destruction for each component in the cycle as well as the first law and exergy efficiencies of the cycle. The optimum operating conditions are established by maximizing the cycle exergy efficiency for the case of a solar heat source. Performance of the cycle over a range of heat source temperatures of 320–460°K was investigated. It is found that increasing the heat source temperature does not necessarily produce higher exergy efficiency, as is the case for first law efficiency. The largest exergy destruction occurs in the absorber, while little exergy destruction takes place in the boiler.

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