ENTROPY PRODUCTION IN A SPONTANEOUS, ADIABATIC (NON-ISOTHERMAL) CHEMICAL REACTION

1959 ◽  
Vol 37 (11) ◽  
pp. 1911-1915
Author(s):  
D. H. Everett
Keyword(s):  
Free Energy ◽  
Entropy Production ◽  
Chemical Reaction ◽  
Internal Combustion Engines ◽  
Heat Engine ◽  
Internal Combustion ◽  
Combustion Engines ◽  
Initial Value ◽  
Definition Of

When a chemical reaction occurs spontaneously and isothermally the loss of useful work is equal to the decrease in free energy of the system. If the same reaction, supposed for example to be exothermic, occurs adiabatically the temperature rises and the system can be used as a source of heat to operate a heat engine: as heat is withdrawn the temperature of the system falls and eventually returns to its initial value. Part of the free energy of the reaction has been recovered as useful work, part lost in the spontaneous irreversible step. Expressions are derived for the loss of useful work and the entropy production in the adiabatic irreversible step, and it is shown that the work lost is equal to T0× (entropy produced) where T0 is the temperature ofthesurroundings. Some consequences of these ideas in relation to the definition of the efficiency of internal combustion engines are considered briefly.

Applying Thermodynamics in Search of Superior Engine Efficiency

2005 ◽  
Vol 127 (3) ◽  
pp. 670-675 ◽  
Author(s):  
Charles A. Amann
Keyword(s):  
Thermal Efficiency ◽  
Internal Combustion Engines ◽  
Combustion Engine ◽  
Heat Engine ◽  
Internal Combustion ◽  
Combustion Engines ◽  
Closed Cycle ◽  
Engine Efficiency ◽  
Operating Cycles ◽  
Thermodynamic Processes

Historically, a succession of thermodynamic processes has been used to idealize the operating cycles of internal combustion engines. In this study, the 256 possible combinations of four reversible processes—isentropic, isothermal, isochoric, and isobaric—are surveyed in search of cycles promising superior thermal efficiency. Regenerative cycles are excluded. The established concept of the air-standard cycle, which mimics the internal combustion engine as a closed-cycle heat engine, is used to narrow the field systematically. The approach relies primarily on graphical interpretation of approximate temperature-entropy diagrams and is qualitative only. In addition to identifying the cycles offering the greatest efficiency potential, the compromise between thermal efficiency and mean effective pressure is addressed.

Applying Thermodynamics in Search of Superior Engine Efficiency

2002 ◽  
Author(s):  
Charles A. Amann
Keyword(s):  
Thermal Efficiency ◽  
Internal Combustion Engines ◽  
Combustion Engine ◽  
Heat Engine ◽  
Internal Combustion ◽  
Combustion Engines ◽  
Closed Cycle ◽  
Engine Efficiency ◽  
Operating Cycles ◽  
Thermodynamic Processes

Historically, a succession of thermodynamic processes has been used to idealize the operating cycles of internal combustion engines. In this study, the 256 possible combinations of four reversible processes – isentropic, isothermal, isochoric, and isobaric – are surveyed in search of cycles promising superior thermal efficiency. Regenerative cycles are excluded. The established concept of the air-standard cycle, which mimics the internal combustion engine as a closed-cycle heat engine, is used to narrow the field systematically. The approach relies primarily on graphical interpretation of approximate temperature-entropy diagrams and is qualitative only. In addition to identifying the cycles offering the greatest efficiency potential, the compromise between thermal efficiency and mean effective pressure is addressed.

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