Reversed Camot engine

Carnot stated that the efficiency of a reversible Camot engine depends only on the temperatures of the heat reservoirs and is independent of the nature of the working substance. This theorem can be proved by showing that the assumption of a reversible engine with any but the known efficiency of a reversible Camot engine leads to a contradiction of the Clausius statement of the second law. 

As the efficiency of a Camot engine is independent of the working substance, the efficiency given in Equation (6.42) for an ideal gas must be equal to that given in Equation (6.29) for any reversible Camot engine operating between the same heat reservoirs. Thus,... 

Comprehensive discussions of fuel cells and Camot engines Nemst law analytical fuel cell modeling reversible losses and Nemst loss and irreversible losses, multistage oxidation, and equipartition of driving forces. Includes new developments and applications of fuel cells in trigeneration systems coal/biomass fuel cell systems indirect carbon fuel cells and direct carbon fuel cells. 

A Camot engine operates between two heat reservoirs in such a way that all heat absorbed is absorbed at the constant temperature of the hot reservoir and all heat rejected is rejected at the constant temperature of the cold reservoir. Any reversible engine operating between two heat reservoirs is a Camot engine an engine operating on a different cycle must necessarily transfer heat across finite temperature differences and therefore cannot be reversible. 

Since a Camot engine is reversible, it may be operated in reverse the Camot cycle is then traversed in the opposite direction, and it becomes a reversible... 

The Camot-engine cycle, described in Chap. 5, operates reversibly and consi of two isothermal steps connected by two adiabatic steps. In the isothermal stc at higher temperature TH, heat < H is absorbed by the working fluid of engine, and in the isothermal step at lower temperature Tc, heat QC is discard... 

The cycle traversed by an ideal gas serving as the working fluid in a Camot engine is shown by a PV diagram in Fig. 5.3. It consists of four reversible steps ... 

These calculations for a reversible cell show that die electrical work output is more dian 90% of die heat tliat would be released (AH) by actual combustion of the fuel. Were diis heat supplied to a Camot engine operating at practical temperature levels, a much smaller... 

Since the work supplied or obtained in each step of the Carnot cycle is expressible in the form — f PdV,th enclosed area on the P-V diagram of Fig. 4.3-26 is equal to the total work supplied hy the Carnot engine to its surroundings in one complete cycle. (You should verify that if the Camot engine is driven in reverse, so that the cycle in Fig. 

A Camot engine working in the reverse direction. Refrigerators and air conditioners supply work to remove heat from a cold heat source and deposit heat q into a hot heat sink. 

The energy transfers involved in one cycle of a Camot engine are shown sehematieally in Fig. 4.5(a). When the cycle is reversed, as shown in Fig. 4.5(b), the deviee is eaUed a Carnot heat pump. In each cycle of a Carnot heat pump, gh is negative and qc is positive. Since each step of a Carnot engine or Carnot heat pump is a reversible process, neither device is an impossible device. 

Just as the Carnot cycle C of Fig. 4.3 can be claimed to be the most efficient possible heat engine ( reai < camot = 1 — Itfc/tfhlX so t0° can reverse Carnot cycle C be claimed to be the most efficient possible refrigerator ... 

Statement of the Camot-Claiisitis principle for an open reversible transformation. Entropy.—These propositions suffice to give a clue to the importance of the principle of Carnot and Claufflus in the theory of heat-engines but the study of the motive power of heat is not our object so let us return to the principle itself and try to put it into such a form that it may be easily applied to the problems of chemical mechanics. 

Nicolas Leonard Sadi Carnot, the French engineer and physicist, was bom in Paris in 1796. His father, Lazare Nicolas Marguerite Carnot, was in the French military service. Sadi Camot is considered as the founder of modem thermodynamics. Famous for his invaluable contributions to science and thermodynamics, Sadi Camot was honored with the title Father of Thermodynamics. Some of his noteworthy contributions to thermodynamics are the concepts of Camot heat engine, Camot cycle, Carnot s theorem, Camot efficiency, and reversible cycle. 

Camot cycle - A sequence of reversible changes in a heat engine using a perfect gas as tbe working substance, which is used to demonstrate that entropy is a state function. The Camot cycle dso provides a means to calculate tbe efficiency of a beat engine. 

A heat engine, as mentioned in Sec. 4.2, is a closed system that converts heat to work and operates in a cycle. A Carnot engine is a particular kind of heat engine, one that performs Carnot cycles with a working substance. A Camot cycle has four reversible steps, alternating isothermal and adiabatic see the examples in Figs. 4.3 and 4.4 in which the working substances are an ideal gas and H2O, respectively. 

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