Thermodynamic Analysis of Part-Flow Cycle Supercritical CO2 Gas Turbines

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
Motoaki Utamura
Keyword(s):  
Heat Exchanger ◽  
Gas Turbines ◽  
Expansion Ratio ◽  
Operating Conditions ◽  
Working Fluid ◽  
Pinch Point ◽  
Regenerative Heat ◽  
Regenerative Heat Exchanger ◽  
Flow Cycle ◽  
Cycle Efficiency

Cycle characteristics of closed gas turbines using supercritical carbon dioxide as a working fluid are investigated. It is found that an anomalous behavior of the physical properties of CO2 at the pseudocritical point may limit the heat exchange rate of a regenerative heat exchanger due to the presence of a pinch point inside the regenerative heat exchanger. Taking such a pinch problem into consideration, the cycle efficiency of the Brayton cycle is assessed. Its value is found to be limited to 39% degraded by 8% compared with the case without the pinch present inside. As an alternative, a part-flow cycle is investigated and its operable range has been identified. It is revealed that the part-flow cycle is effective to recover heat transfer capability and may achieve the cycle thermal efficiency of 45% under maximum operating conditions of 20 MPa and 800 K. Optimal combination of turbine expansion ratio and a part-flow ratio is 2.5 and 0.68, respectively. Parametric study is carried out. In neither compressor nor turbine, deteriorated adiabatic efficiency may affect cycle efficiency significantly. However, pressure drop characteristics of heat exchangers govern the cycle efficiency.

Thermodynamic Analysis of Part-Flow Cycle Supercritical CO2 Gas Turbines

2008 ◽  
Author(s):  
Motoaki Utamura
Keyword(s):  
Heat Exchanger ◽  
Gas Turbines ◽  
Expansion Ratio ◽  
Operating Conditions ◽  
Working Fluid ◽  
Pinch Point ◽  
Regenerative Heat ◽  
Regenerative Heat Exchanger ◽  
Flow Cycle ◽  
Cycle Efficiency

Cycle characteristics of closed gas turbines using super critical carbon dioxide as a working fluid are investigated. It is found an anomalous behavior of physical properties of CO2 at pseudo-critical point may limit heat exchange rate of a regenerative heat exchanger due to the presence of pinch point inside the regenerative heat exchanger. Taking such pinch problem into consideration, the cycle efficiency of Brayton cycle is assessed. Its value is found limited to 39% degraded by 8% compared with the case without the pinch present inside. As an alternative a part flow cycle is investigated and its operable range has been identified. It is revealed that the part flow cycle is effective to recover heat transfer capability and may achieve the cycle thermal efficiency of 45% under maximum operating conditions of 20MPa and 800K. Optimal combination of turbine expansion ratio and a part flow ratio is 2.5 and 0.68 respectively. Parametric study is carried out. In neither compressor nor turbine, deteriorated adiabatic efficiency may affect cycle efficiency significantly. However, pressure drop characteristics of heat exchangers govern the cycle efficiency.

scholarly journals Experimental Investigation of a Small-Scale ORC Power Plant Using a Positive Displacement Expander with and without a Regenerator

Energies ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1452 ◽  
Author(s):  
Collings ◽  
Mckeown ◽  
Wang ◽  
Yu
Keyword(s):  
Heat Exchanger ◽  
Power Plants ◽  
Large Scale ◽  
Internal Heat ◽  
Expansion Ratio ◽  
Operating Conditions ◽  
Working Fluid ◽  
Small Scale ◽  
Regenerative Heat ◽  
Positive Displacement

While large-scale ORC power plants are a relatively mature technology, their application to small-scale power plants (i.e., below 10 kW) still encounters some technical challenges. Positive displacement expanders are mostly used for such small-scale applications. However, their built-in expansion ratios are often smaller than the expansion ratio required for the maximum utilisation of heat sources, leading to under expansion and consequently higher enthalpy at the outlet of the expander, and ultimately resulting in a lower thermal efficiency. In order to overcome this issue, one possible solution is to introduce an internal heat exchanger (i.e., the so-called regenerator) to recover the enthalpy exiting the expander and use it to pre-heat the liquid working fluid before it enters the evaporator. In this paper, a small-scale experimental rig (with 1-kW rated power) was designed and built that is capable of switching between regenerative and non-regenerative modes, using R245fa as the working fluid. It has been tested under various operating conditions, and the results reveal that the regenerative heat exchanger can recover a considerable amount of heat when under expansion occurs, increasing the cycle efficiency.

A Solar Gas Turbine Cycle With Super-Critical Carbon Dioxide as a Working Fluid

2006 ◽  
Author(s):  
Motoaki Utamura ◽  
Yutaka Tamaura
Keyword(s):  
Carbon Dioxide ◽  
Heat Exchanger ◽  
Molten Salt ◽  
Gas Turbine ◽  
Thermal Power ◽  
Working Fluid ◽  
Regenerative Heat ◽  
Operation Conditions ◽  
Gas Turbine Cycle ◽  
Cycle Efficiency

Solar thermal power generation system equipped with molten salt thermal storage offers continuous operation at a rated power independent of the variation of insolation. A gas turbine cycle for solar applications is studied which works in a moderate temperature range (600–850K) where molten salt stays as liquid stably. It is found that a closed cycle with super-critical state of carbon dioxide as a working fluid is a promising candidate for solar application. The cycle featured in smaller compressor work would achieve high cycle efficiency if cycle configuration and operation conditions are chosen properly. The temperature effectiveness of a regenerative heat exchanger is shown to govern the efficiency. Under the condition of 98% temperature effectiveness, the regenerative cycle with pre- and inter-cooling provides cycle efficiency of as much as 47%. A novel heat exchanger design to realize such a high temperature effectiveness is also presented.

Heat Exchanger Design Considerations for Gas Turbine HTGR Power Plant

1977 ◽  
Vol 99 (2) ◽  
pp. 237-245 ◽  
Author(s):  
C. F. McDonald ◽  
T. Van Hagan ◽  
K. Vepa
Keyword(s):  
Heat Exchanger ◽  
Power Plant ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Power Conversion ◽  
Structural Safety ◽  
Working Fluid ◽  
Closed Cycle ◽  
High Degree ◽  
Cycle Efficiency

The Gas Turbine High Temperature Gas Cooled Reactor (GT-HTGR) power plant combines the existing design HTGR core with a closed-cycle helium gas turbine power conversion system directly in the reactor primary circuit. Unlike open-cycle gas turbines where the recuperative heat exchanger is an optional component, the high cycle efficiency of the nuclear closed-cycle gas turbine is attributable to a high degree to the incorporation of the recuperator (helium-to-helium) and precooler (helium-to-water) exchangers in the power conversion loop. For the integrated plant configuration, a nonintercooled cycle with a high degree of heat recuperation was selected on the basis of performance and economic optimization studies. A recuperator of high effectiveness was chosen because it significantly reduces the optimum pressure ratio (for maximum cycle efficiency), and thus reduces the number of compressor and turbine stages for the low molecular weight, high specific heat, helium working fluid. Heat rejection from the primary system is effected by a helium-to-water precooler, which cools the gas to a low level prior to compression. The fact that the rejection heat is derived from the sensible rather than the latent heat of the cycle working fluid results in dissipation over a wide band of temperature, the high average rejection temperature being advantageous for either direct air cooling or for generation of power in a waste heat cycle. The high heat transfer rates in the recuperator (3100 MWt) and precooler (1895 MWt), combined with the envelope restraints associated with heat exchanger integration in the prestressed concrete reactor vessel, require the use of more compact surface geometries than in contemporary power plant steam generators. Various aspects of surface geometry, flow configuration, mechanical design, fabrication, and integration of the heat exchangers are discussed for a plant in the 1100 MWe class. The influence of cycle parameters on the relative sizes of the recuperator and precooler are also presented. While the preliminary designs included are not meant to represent final solutions, they do embody features that satisfy many of the performance, structural, safety, and economic requirements.

Review of Computer Simulations of Regenerative Heat Exchangers

1978 ◽  
Vol 11 (8) ◽  
pp. 309-312
Author(s):  
A. J. Willmott
Keyword(s):  
Heat Exchanger ◽  
Recent Work ◽  
Computer Simulations ◽  
Heat Exchangers ◽  
Operating Conditions ◽  
Design Criteria ◽  
Regenerative Heat ◽  
Regenerative Heat Exchanger ◽  
Fuel Savings

Early models of the stationary performance of the regenerative heat exchanger are discussed together with more recent work in which the behaviour under chronologically varying operating conditions is simulated. The need is presented for better control facilities and possibly new design criteria if fuel savings in regenerative heat exchanger non-stationary operations are to be effected.

scholarly journals Parametric Study of Various Thermodynamic Cycles for the Use of Unconventional Blends

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4656
Author(s):  
Odi Fawwaz Alrebei ◽  
Philip Bowen ◽  
Agustin Valera Medina
Keyword(s):  
Working Conditions ◽  
Parametric Study ◽  
Gas Turbines ◽  
Carbon Capture ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Simple Cycle ◽  
Working Fluid ◽  
Specific Work ◽  
Cycle Efficiency

This paper aims to conduct a parametric study for five gas turbine cycles (namely, simple, heat exchanged, free turbine and simple cycle, evaporative, and humidified) using a CO2-argon-steam-oxyfuel (CARSOXY) mixture as a working fluid to identify their optimal working conditions with respect to cycle efficiency and specific work output. The performance of the five cycles using CARSOXY is estimated for wet and dry compression, and a cycle is suggested for each range of working conditions. The results of this paper are based on MATLAB codes, which have been developed to conduct the cycle analysis for CARSOXY gas turbines, assuming a stoichiometric condition with an equivalence ratio of 1.0. Analyses are based on the higher heating value (HHV) of methane as fuel. This paper also identifies domains of operating conditions for each cycle, where the efficiency of CARSOXY cycles can be increased by up to 12% compared to air-driven cycles. The CARSOXY heat exchanged cycle has the highest efficiency among the other CARSOXY cycles in the compressor pressure ratio domain of 2–3 and 6–10, whereas, at 3–6, the humidified cycle has the highest efficiency. The evaporative cycle has intermediate efficiency values, while the simple cycle and the free turbine-simple cycle have the lowest efficiencies amongst the five cycles. Additionally, a 10% increase in the cycle efficiency can be theoretically achieved by using the newly suggested CARSOXY blend that has the molar fractions of 47% argon, 10% carbon dioxide, 10% H2O, and 33% oxyfuel at low compressor inlet temperatures, thus theoretically enabling the use of carbon capture technologies.

A Regenerative Heat Exchanger for Livestock Buildings

1984 ◽  
Vol 27 (5) ◽  
pp. 1505-1510
Author(s):  
W. P. Lampman ◽  
E. B. Moysey
Keyword(s):  
Heat Exchanger ◽  
Regenerative Heat ◽  
Regenerative Heat Exchanger ◽  
Livestock Buildings
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