scholarly journals Splitting Physical Exergy by Its Feasible Working Ways

Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 2091
Author(s):  
Dongbo Gao ◽  
Xiaoqi Peng ◽  
Yanpo Song ◽  
Ping Zhou
Keyword(s):  
Exergy Analysis ◽  
Thermal Power ◽  
Splitting Method ◽  
Computational Method ◽  
New Method ◽  
Inlet Temperature ◽  
Working Ability ◽  
The Real ◽  
Power Cycle ◽  
Mathematical Derivation

This paper analyzed the problems associated with physical exergy splitting, and based on this, presented a new splitting method. This new method splits the physical exergy into three parts according to the feasible working ways, i.e.,: the direct, indirect, and adaptive exergy. The computational method and the physical meaning of the three exergy parts were presented in detail in terms of graphic representation and mathematical derivation. Then, it was applied to the exergy analysis of a thermal power cycle. The results show that compared with the conventional method which splits the physical exergy into thermal and mechanical parts, the current exergy splitting method can better represent the change rule of the working ability of the real working stream in the cycle and the influence of some operation parameters, such as the turbine inlet temperature, on the real working ability. The study suggests that the new method can make the exergy analysis more helpful and guidable in its applications.

scholarly journals Advanced Exergy Analysis of Waste-Based District Heating Options through Case Studies

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4766
Author(s):  
Huseyin Gunhan Ozcan ◽  
Arif Hepbasli ◽  
Aysegul Abusoglu ◽  
Amjad Anvari-Moghaddam
Keyword(s):  
Real Time ◽  
Heat Exchangers ◽  
Exergy Analysis ◽  
Thermal Power ◽  
District Heating ◽  
Exergy Efficiency ◽  
Hot Water ◽  
Exergy Destruction ◽  
District Heating System ◽  
The Real

The heating of the buildings, together with domestic hot water generation, is responsible for half of the total generated heating energy, which consumes half of the final energy demand. Meanwhile, district heating systems are a powerful option to meet this demand, with their significant potential and the experience accumulated over many years. The work described here deals with the conventional and advanced exergy performance assessments of the district heating system, using four different waste heat sources by the exhaust gas potentials of the selected plants (municipal solid waste cogeneration, thermal power, wastewater treatment, and cement production), with the real-time data group based on numerical investigations. The simulated results based on conventional exergy analysis revealed that the priority should be given to heat exchanger (HE)-I, with exergy efficiency values from 0.39 to 0.58, followed by HE-II and the pump with those from 0.48 to 0.78 and from 0.81 to 0.82, respectively. On the other hand, the simulated results based on advanced exergy analysis indicated that the exergy destruction was mostly avoidable for the pump (78.32–78.56%) and mostly unavoidable for the heat exchangers (66.61–97.13%). Meanwhile, the exergy destruction was determined to be mainly originated from the component itself (endogenous), for the pump (97.50–99.45%) and heat exchangers (69.80–91.97%). When the real-time implementation was considered, the functional exergy efficiency of the entire system was obtained to be linearly and inversely proportional to the pipeline length and the average ambient temperature, respectively.

Single-level anterior cervical fusion: a new method to evaluate the real need for plate augmentation

2019 ◽  
Vol 63 (4) ◽  
Author(s):  
Marco Ajello ◽  
Nicola Marengo ◽  
Paolo Pacca ◽  
Federico Pecoraro ◽  
Francesco Zenga ◽  
...  
Keyword(s):  
Anterior Cervical Fusion ◽  
New Method ◽  
Cervical Fusion ◽  
The Real ◽  
Single Level

Numerical Investigation of the Cooling Performance on the Endwall With and Without Fillet

2018 ◽  
Author(s):  
Qingzong Xu ◽  
Qiang Du ◽  
Pei Wang ◽  
Jun Liu ◽  
Guang Liu
Keyword(s):  
Secondary Flow ◽  
Turbulence Model ◽  
Film Cooling ◽  
Computational Method ◽  
Inlet Temperature ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Numerical Predictions ◽  
Turbine Vane

High inlet temperature of turbine vane increases the demand of high film cooling effectiveness. Vane endwall region was extensively cooled due to the high and flat exit temperature distribution of combustor. Leakage flow from the combustor-turbine gap was used to cool the endwall region except for preventing hot gas ingestion. Numerical predictions were conducted to investigate the flow structure and adiabatic film cooling effectiveness of endwall region in a linear cascade with vane-endwall junction fillet. The simulations were completed by solving the three-dimensional Reynolds-Averaged Navier-Stokes(RANS) equations with shear stress transport(SST) k-ω turbulence model, meanwhile, the computational method and turbulence model were validated by comparing computational result with the experiment. Three types of linear fillet with the length-to-height ratio of 0.5, 1 and 2, named fillet A, fillet B and fillet C respectively, were studied. In addition, circular fillet with radius of 2mm was compared with linear fillet B. The interrupted slot, produced by changing the way of junction of combustor and turbine vane endwall, is introduced at X/Cax = −0.2 upstream of the vane leading edge. Results showed that fillet can significantly affect the cooling performance on the endwall due to suppressing the strength of the secondary flow. Fillet C presented the best cooling performance comparing to fillet A and fillet B because a portion of the coolant which climbs to the fillet was barely affected by secondary flow. Results also showed the effect of fillet on the total pressure loss. The result indicated that only fillet A slightly decreases endwall loss.

Exergetic comparison of two different cooling technologies for the power cycle of a thermal power plant

Energy ◽  
2011 ◽  
Vol 36 (4) ◽  
pp. 1966-1972 ◽  
Author(s):  
Ana M. Blanco-Marigorta ◽  
M. Victoria Sanchez-Henríquez ◽  
Juan A. Peña-Quintana
Keyword(s):  
Power Plant ◽  
Thermal Power Plant ◽  
Thermal Power ◽  
Power Cycle

scholarly journals Bounding Lagrangian widths via geodesic paths

2014 ◽  
Vol 150 (12) ◽  
pp. 2143-2183 ◽  
Author(s):  
Matthew Strom Borman ◽  
Mark McLean
Keyword(s):  
Sectional Curvature ◽  
New Method ◽  
Finite Width ◽  
Energy Capacity ◽  
Positive Sectional Curvature ◽  
Floer Cohomology ◽  
The Real ◽  
Ambient Manifold ◽  
Open Map ◽  
Geodesic Paths

AbstractThe width of a Lagrangian is the largest capacity of a ball that can be symplectically embedded into the ambient manifold such that the ball intersects the Lagrangian exactly along the real part of the ball. Due to Dimitroglou Rizell, finite width is an obstruction to a Lagrangian admitting an exact Lagrangian cap in the sense of Eliashberg–Murphy. In this paper we introduce a new method for bounding the width of a Lagrangian$Q$by considering the Lagrangian Floer cohomology of an auxiliary Lagrangian$L$with respect to a Hamiltonian whose chords correspond to geodesic paths in$Q$. This is formalized as a wrapped version of the Floer–Hofer–Wysocki capacity and we establish an associated energy–capacity inequality with the help of a closed–open map. For any orientable Lagrangian$Q$admitting a metric of non-positive sectional curvature in a Liouville manifold, we show the width of$Q$is bounded above by four times its displacement energy.

Analytical Formulation of the Performance of the Allam Power Cycle

2020 ◽  
Author(s):  
Yousef Haseli
Keyword(s):  
Power Plants ◽  
Fossil Fuels ◽  
Air Separation ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Separation Unit ◽  
Power Cycle ◽  
Functional Relationships ◽  
Oxyfuel Combustion ◽  
Co2 Flow

Abstract Thermal power plants operating on fossil fuels emit a considerable amount of polluting gases including carbon dioxide and nitrogen oxides. Several technologies have been developed or under development to avoid the emissions of, mainly, CO2 that are formed as a result of air-fuel combustion. While post-combustion capture methods are viable solutions for reduction of CO2 in the existing power plants, implementation of the concept of oxyfuel combustion in future power cycles appears to be a promising technique for clean power generation from fossil fuels. A novel power cycle that employs oxyfuel combustion method has been developed by NET Power. Known as the Allam cycle, it includes a turbine, an air separation unit (ASU), a combustor, a recuperator, a water separator, CO2 compression with intercooling and CO2 pump. (Over 90% of the supercritical CO2 flow is recycled back to the cycle as the working fluid, and the rest is extracted for further processing and storage. The present paper introduces a simplified thermodynamic analysis of the Allam power cycle. Analytical expressions are derived for the net power output, optimum turbine inlet temperature (TIT), and the molar flowrate of the recycled CO2 flow. The study aims to provide a theoretical framework to help understand the functional relationships between the various operating parameters of the cycle. The optimum TIT predicted by the presented expression is 1473 K which is fairly close to that reported by the cycle developers.

scholarly journals The analysis of a Velox-type CHP plant for various gaseous fuels

2019 ◽  
Vol 137 ◽  
pp. 01001
Author(s):  
Krystian Smolka ◽  
Slawomir Dykas
Keyword(s):  
Power Plant ◽  
Waste Heat ◽  
Thermal Power ◽  
Combined Heat And Power ◽  
Power Cycle ◽  
Gaseous Fuels ◽  
University Of Technology ◽  
Gas Power Plant ◽  
Steam System ◽  
Small Capacity

For many years, the Institute of Power Engineering and Turbomachinery of the Silesian University of Technology has been using a small-capacity (about 500 kWe) steam-gas power plant. Based on many yearsof experience in operation of this power plant utilizing the Velox-type gas-steam system, an idea arose to modify this type of thermal power cycle to create a combined heat and power (CHP) plant of small capacity, dedicated for distributed heat and power production of the range up to 500 kW or production process steam with high temperature. Previous thermodynamic and economic analysis of that type of CHP plant were conducted for natural gas as afuel. The new idea is use the alternative gas fuels or waste heat for Velox-type CHP plant. An adaptation of the Velox-type CHP plant for various fuelscan be done in simple way by moving the combustion chamber out from the setof heat exchangers, in similar way as it is done for HRSG. This paper presents a thermodynamic analysis of the Velox-type steam-gas cycle fired with various alternative gas fuels such as coke gas, blast furnace gas, biogas orgas from gasification. The systems are modelled in the EBSILON® Professional 13 program.

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