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.

Application of Supercritical Pressures in Power Engineering

2017 ◽  
pp. 404-457
Author(s):  
Igor Pioro ◽  
Mohammed Mahdi ◽  
Roman Popov
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
High Temperature ◽  
Gas Turbine ◽  
Power Plants ◽  
Thermal Power ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Thermal Power Plants ◽  
Power Cycles

SuperCritical Fluids (SCFs) have unique thermophyscial properties and heat-transfer characteristics, which make them very attractive for use in power industry. In this chapter, specifics of thermophysical properties and heat transfer of SCFs such as water, carbon dioxide and helium are considered and discussed. Also, particularities of heat transfer at SuperCritical Pressures (SCPs) are presented, and the most accurate heat-transfer correlations are listed. SuperCritical Water (SCW) is widely used as the working fluid in the SCP Rankine “steam”-turbine cycle in fossil-fuel thermal power plants. This increase in thermal efficiency is possible by application of high-temperature reactors and power cycles. Currently, six concepts of Generation-IV reactors are being developed, with coolant outlet temperatures of 500°C~1000°C. SCFs will be used as coolants (helium in GFRs and VHTRs; and SCW in SCWRs) and/or working fluids in power cycles (helium; mixture of nitrogen (80%) and helium [20%]; nitrogen, and carbon dioxide in Brayton gas-turbine cycles; and SCW “steam” in Rankine cycle).

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.

Optimization of an air-cooled hybrid gas turbine cycle (Brayton/Ericsson)

2003 ◽  
Vol 217 (3) ◽  
pp. 233-238 ◽  
Author(s):  
T. H. Frost ◽  
A anderson ◽  
B Agnew ◽  
I Potts
Keyword(s):  
Heat Exchanger ◽  
Gas Turbine ◽  
Cycle Performance ◽  
Specific Power ◽  
Air Cooling ◽  
Performance Parameters ◽  
Air Cooled Heat Exchanger ◽  
Gas Turbine Cycle ◽  
Cycle Efficiency ◽  
Cycle Temperature

The performance of a Brayson cycle, a hybrid gas turbine cycle, has been examined to establish the effect of air cooling and heat exchanger effectiveness on the cycle efficiency and specific power. The air-cooled heat exchanger was optimized to produce the maximum net efficiency for the specified minimum cycle temperature. The cycle performance was shown to be adversely influenced by the air cooling as it reduced both the specific power and efficiency. The heat exchanger effectiveness was shown to have a secondary impact on the performance parameters. An additional optimization of the heat exchanger at minimum volume is also presented to act as a benchmark against which the performance of the heat exchanger in the optimized cycle can be compared.

Novel Gas Turbine Cycle With Integration of CO2 Recovery and LNG Cryogenic Exergy Utilization

2002 ◽  
Author(s):  
Shimin Deng ◽  
Hongguang Jin ◽  
Ruixian Cai ◽  
Rumou Lin
Keyword(s):  
Gas Turbine ◽  
Greenhouse Gas Emission ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Average Temperature ◽  
Co2 Recovery ◽  
Gas Turbine Cycle ◽  
Cycle Efficiency ◽  
Very High ◽  
Turbine Exhaust

In this paper we propose a new gas turbine cycle, which employs a semi-closed recuperative gas turbine with LNG utilization. Nitrogen is selected as working fluid with air induced at the inlet of compressor. The inlet temperature of the compressor is kept pretty low with LNG cooling, and turbine inlet temperature can be very high because of internal combustion, and higher average temperature of heat absorption of the cycle is achieved due to recuperation. As a result, the cycle efficiency can reach as high as 70% (TIT=1250°C). Furthermore, along the process of LNG vaporization, turbine exhaust is cooled down; CO2 in the mixture is solidified and separated without extra power consumption. Two different natural gas sendout pressures (7.0 and 3.0 MPa) are considered. Their performances are simulated and a comprehensive analysis is carried out. The performance of the new cycle, CO2 recovery, and heat transfer in LNG vaporizer are discussed in detail. The new cycle proposed here is based on the integration of carbon dioxide recovery and LNG cryogenic exergy utilization, and it will contribute to both improvement on power generation efficiency and reduction of greenhouse gas emission.

scholarly journals A Novel Spherical Packed Bed Application on Decentralized Heat Recovery Ventilation Units

2019 ◽  
Vol 111 ◽  
pp. 01012
Author(s):  
Alper Mete GENC ◽  
Ziya Haktan KARADENIZ ◽  
Orhan EKREN ◽  
Macit TOKSOY
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Recovery ◽  
Thermal Power ◽  
Packed Bed ◽  
Small Scale ◽  
Regenerative Heat ◽  
Operation Conditions ◽  
Cyclic Operation ◽  
Wide Range

Decentralized heat recovery ventilation (HRV) systems are assumed as simple solutions to obtain a healthy and comfortable indoor environment. A wall or window mounted compact version of decentralized HRV systems (mono unit) are used for small scale, mostly residential applications. A fan and a heat exchanger are the critical components of this compact system. The flow capacity of these units are down to 10 m3/h, where efficiencies over 90% are commonly declared by the manufacturers. On the other hand, spherical packed beds (SPD) are widely used in the heat transfer applications such as; chemical reactors, grain driers, nuclear reactors, thermal storage in buildings and in solar thermal power plants, due to operational convenience. These systems are operated under steady flow conditions, unlike decentralized HRV systems which are designed for cyclic operation. In this study, heat recovery performance of a spherical packed bed heat exchanger for a decentralized HRV system is investigated. A one dimensional mathematical model for a SPD is obtained and an in-house computer code is developed to solve the transient heat transfer inside the packed bed under cyclic operation conditions. Well known convenient correlations were used for pressure drop calculations. A number of bed and sphere diameters were studied in a wide range. Various flow time and number of cycles were studied for the hot and cold flow to understand the SPD performance for HRV applications. This novel application also has the potential for regenerative heat recovery systems.

Some Alternative Technologies for Solar Thermal Power Generation

Solar Energy ◽  
2006 ◽  
Author(s):  
Motoaki Utamura ◽  
Yutaka Tamaura ◽  
Hiroshi Hasuike
Keyword(s):  
Heat Exchanger ◽  
Thermal Power ◽  
Thermal Design ◽  
Optical Systems ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Regenerative Heat ◽  
Turbine Inlet ◽  
The Cross ◽  
Field Efficiency

Two advanced optical systems and a highly efficient thermal cycle suitable for beam-down power tower with thermal storage are presented. (1) To increase field efficiency, the “cross beam” heliostat array concept is proposed. Using continuum optical model, the characteristics of the cross beam concept and its economy were investigated. (2) To protect the central reflector (CR) against wind force, a “multi-ring CR” concept is proposed. The concentration performance of multi-ring CRs is calculated using the ray-tracing method. It shows no worse results than the case with a single hyperboloid mirror. (3) The potential of a closed gas turbine cycle with supercritical carbon dioxide as a working fluid was investigated. An optimal cycle configuration involves a regenerative cycle with pre-cooling and inter-cooling cycles, in which theoretically achievable cycle thermal efficiency is 47% at the turbine inlet temperature of 800 K and turbine inlet pressure of 20 MPa. Detailed thermal design of a critical component, regenerative heat exchanger (RHX) is carried out using a newly developed printed heat exchanger (PCHE). It proved to be a feasible design.

Thermal-Hydraulic Characteristics of Microchannel Heat Exchanger and Its Application to Solar Gas Turbines

2007 ◽  
Author(s):  
Motoaki Utamura
Keyword(s):  
Carbon Dioxide ◽  
Heat Exchanger ◽  
Gas Turbines ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Working Fluid ◽  
Microchannel Heat Exchanger ◽  
Pressure Loss Coefficient ◽  
Wide Range ◽  
Gas Turbine Cycle

Incorporating “integral method” proposed here, a set of empirical correlations of local heat transfer coefficient and pressure loss coefficient are newly derived based on experiments using microchannel heat exchanger (MCHE) with supercritical carbon dioxide as heating medium and water as coolant. They are expressed in dimensionless forms of polynomial of Reynolds number and Prandtl number. The same correlation of Nusselt number is found applicable to both fluids and its value is almost two times larger than Dittus Boelter correlation. It was also shown that the above form is applicable to a wide range of geometry with the values of constants changed. Accuracy of both correlations is confirmed within 5% errors for MCHE with S-shaped fins in the range of pressures 9∼12.5MPa and temperatures 280∼390K. Based on the correlations, sizes of heat exchangers are evaluated contained in gas turbine cycle with super critical carbon dioxide as a working fluid applicable to solar power.

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 The Effect of Heat Exchanger Effectiveness and Exergy Loss in the Estimation of Cycle Efficiency

1998 ◽  
Author(s):  
J. H. Horlock
Keyword(s):  
Heat Exchanger ◽  
Gas Turbine ◽  
Heat Exchangers ◽  
Exergy Loss ◽  
Cycle Performance ◽  
Gas Turbine Cycle ◽  
Cycle Efficiency ◽  
The Relationship ◽  
Exergy Losses

The effect of heat exchanger effectiveness on cycle efficiency is well known. But the relationship between exergy loss in heat exchangers and the effectiveness is less well documented. In this paper the relationship is explored; it is shown how the exergy loss in the heat exchanger is changed as effectiveness is altered. It is also shown how the exergy losses in other components of the recuperative gas turbine cycle are changed, together with the overall cycle performance, as the effectiveness is varied.

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.

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