Finite-Time Thermodynamic Analysis of Combined Heat Engines

1997 ◽  
Vol 25 (4) ◽  
pp. 281-289 ◽  
Author(s):  
Mamdouh El Haj Assad
Keyword(s):  
Power Output ◽  
Finite Time ◽  
Combined Cycle ◽  
Maximum Power ◽  
Efficiency Ratio ◽  
Lower Efficiency ◽  
Maximum Power Output ◽  
Heat Engines ◽  
Output Ratio ◽  
Cycle Efficiency

The maximum power output and the efficiency at that power of a combined heat engines are analysed by using Curzon and Ahlborn's finite-time analysis. The efficiency at the maximum power of the combined reversible and irreversible heat engines has been obtained. This work also shows that when the engines are internally irreversible, the combined cycle delivers less power and has lower efficiency than an endoreversible combined heat engines. An expression is derived to relate the maximum power output ratio (irreversible/endoreversible) to the corresponding cycle efficiency ratio. It is shown by that relation that the efficiency ratio is much higher than the power ratio and they become identical when the irreversible cycle is very close to the endoreversible one.

scholarly journals Optimal temperatures and maximum power output of a complex system with linear phenomenological heat transfer law

2009 ◽  
Vol 13 (4) ◽  
pp. 33-40 ◽  
Author(s):  
Lingen Chen ◽  
Jun Li ◽  
Fengrui Sun
Keyword(s):  
Complex System ◽  
Heat Transfer ◽  
Power Output ◽  
Finite Time ◽  
Heat Engine ◽  
Thermal Capacity ◽  
Maximum Power ◽  
Finite Time Thermodynamics ◽  
Maximum Power Output ◽  
Different Temperatures

A complex system including several heat reservoirs, finite thermal capacity subsystems with different temperatures and a transformer (heat engine or refrigerator) with linear phenomenological heat transfer law [q ? ?(T -1)] is studied by using finite time thermodynamics. The optimal temperatures of the subsystems and the transformer and the maximum power output (or the minimum power needed) of the system are obtained.

Power Reserve Control for Gas Turbines in Combined Cycle Applications

2011 ◽  
Author(s):  
Eric A. Mu¨ller ◽  
Andrew Wihler
Keyword(s):  
Power Plant ◽  
Electricity Market ◽  
Power Output ◽  
Gas Turbines ◽  
Optimal Operation ◽  
Combined Cycle ◽  
Maximum Power ◽  
Frequency Regulation ◽  
Combined Cycle Power Plant ◽  
Maximum Power Output

In order to be able to optimally operate a combined cycle power plant in a liberalized electricity market, knowledge of the plant’s maximum exportable power generation capacity is vital. However, the maximum power output of a power plant is affected by numerous variable factors, such as the ambient conditions at the plant site. In addition, the allowable plant operating range might be narrowed by a compulsory reserve margin, if the power plant is participating in a frequency regulation program. In this paper, a power reserve controller is derived, which facilitates the optimal operation of a combined cycle gas turbine power plant subject to a reserve margin requirement. The power reserve controller bases on a mathematical description of the power plant and uses an adaptation mechanism to predict on a real-time basis the maximum allowable plant load limit. Based on tests on a single shaft combined cycle power plant, the operation of the power reserve controller is demonstrated and its performance is assessed. The test results prove that the controller predicts the maximum power output of the plant with high accuracy and that it is able to maintain a desired reserve capacity for frequency response as specified.

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