Optimal configuration of a class of endoreversible heat-engines for maximum power-output with linear phenomenological heat-transfer law

2007 ◽  
Vol 84 (9) ◽  
pp. 944-957 ◽  
Author(s):  
Jun Li ◽  
Lingen Chen ◽  
Fengrui Sun
Keyword(s):  
Heat Transfer ◽  
Power Output ◽  
Maximum Power ◽  
Optimal Configuration ◽  
Maximum Power Output ◽  
Heat Engines

Maximum Power From Fluid Flow: Results From the First and Second Laws of Thermodynamics

2012 ◽  
Author(s):  
German Amador Diaz ◽  
John Turizo Santos ◽  
Elkin Hernandez ◽  
Ricardo Vasquez Padilla ◽  
Lesme Corredor
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Power Output ◽  
Power Plants ◽  
Cross Sectional Area ◽  
Maximum Power ◽  
Sectional Area ◽  
Cross Sectional ◽  
Maximum Power Output ◽  
Piston Cylinder

The heat transfer principle of power maximization in power plants with heat transfer irreversibilities was cleverly extended by Bejan [1] to fluid flow, by obtaining that the energy conversion efficiency at maximum power is ηmax = 1/2(1 − P2/P1). This result is analog to the efficiency at maximum power for power plants, ηmax = 1 − (T2/T1)1/2 which was deduced by Curzon and Ahlborn [2]. In this paper, the analysis to obtain maximum power output delivered from a piston between two pressure reservoir across linear flow resistance is generalized by considering the piston cylinder friction, by obtaining relations of maximum power output and optimal speed of the piston in terms of first law efficiency. Expressions to relate the power output, cross sectional area of the chamber and first law efficiency, were deduced in order to evaluate the influence of the overall size constraints and fluid regime in the performance of the piston cylinder system. Flow in circular ducts and developed laminar flow between parallel plates, are considered to demonstrate that when two pressure reservoirs oriented in counterflow, with different and arbitrary cross sectional area, must have the same area in order to maximize the power output of the system. These results introduce some modifications to the results obtained by Bejan [1] and Chen [3]. This paper extends the Bejan and Chen’s work by estimating under turbulent regime the lost available work rate associated with the degree of irreversibilities caused by the flow resistances of the system. This analysis is equivalent to evaluate the irreversibilities in an endoirreversible Carnot heat engine model caused by the heat resistance loss between the engine and its surrounding heat reservoirs. This paper concludes with an application to illustrate the practical applications by estimating the lost available work of an actual steady-flow turbine and the layout pipes upstream and downstream of the same device.

The Efficiency at Maximum Power Output of a Carnot Engine with Heat Leak

1995 ◽  
Vol 23 (2) ◽  
pp. 157-165 ◽  
Author(s):  
F. Moukalled ◽  
R. Y. Nuwayhid
Keyword(s):  
Heat Transfer ◽  
Power Output ◽  
Maximum Power ◽  
Heat Leak ◽  
Suggested Model ◽  
Maximum Power Output ◽  
Transfer Processes ◽  
Newton’S Law ◽  
New Formulation ◽  
Special Case

Endoreversible thermodynamics are used for studying the performance of Carnot engines with heat leak. This is done by adding a heat leak term into a variation of the model suggested by DeVos [1]. Heat transfer across the engine is assumed to occur via a conduction/convection mechanism and Newton's law of cooling is employed to model the heat transfer processes. The efficiency at maximum power output is found to be deeply affected by the rate of heat leak. Moreover, the Curzon-Ahlborn relation [2] is shown to represent a special case of the new formulation. Since the suggested model allows more flexibility in predicting actual engines' performance, its use is recommended in thermodynamics courses.

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