Carnot cycle-based engines

There are now two ways to increase the efficiency of energy conversion from the chemical state into the much-required electricity. They are to use binary or even tertiary systems (e.g. gas turbine -H steam turbine + Organic Rankine Cycle), or to use non-heat cycle based engines— thereby working around the Carnot limitation. 

Heat and temperature were poorly understood prior to Carnot s analysis of heat engines in 1824. The Carnot cycle became the conceptual foundation for the definition of temperature. This led to the somewhat later work of Lord Kelvin, who proposed the Kelvin scale based upon a consideration of the second law of thermodynamics. This leads to a temperature at which all the thermal motion of the atoms stops, By using this as the zero point or absolute zero and another reference point to determine the size of the degrees, a scale can be defined. The Comit e Consultative of the International Committee of Weights and Measures selected 273.16 K as the value lor the triple point for water. This set the ice-point at 273.15 K. 

The second law is independent of the first law. Historically, the second law was generally accepted and understood before acceptance of the first law. Therefore, we base the discussion on the efficiency of a reversible heat engine used in a Carnot cycle. If the efficiency of a reversible heat engine... 

The classic definition of temperature is based upon thermodynamics. Any suitable relation, based on the laws of thermodynamics, can be used to describe temperature on a thermodynamic scale. The two most commonly used relations are the efficiency of the reversible engine (the Carnot cycle) and the intensity of blackbody radiation (Planck s Law) expressed mathematically by... 

The hydride compressor is a form of "heat engine" based on the Carnot cycle. Its energy efficiency is about 50% of Carnot efficiency. Carnot efficiency is based on the temperature difference between the hot energy source and the cold heat sink. Efficiency plotted as a function of hot water (energy source) temperature appears in Figure 2. 

In 1824 a French engineer, Sadi Carnot, investigated the principles governing the transformation of thermal energy, heat, into mechanical energy, work. He based his discussion on a cyclical transformation of a system that is now called the Carnot cycle. The... 

Sadi Carnot s most valuable contribution to thermodynamics is Carnot s ideal heat engine operating with Carnot cycle. His works on ideal heat engine provided the foundation for quantitative mathematical formulation of Carnot efficiency based on Carnot s theorem. However, Carnot s research findings were not well known until another scientist Benoit Pierre Emile Clapeyron followed in his footsteps and experimented with the change in pressure and volume of the processes of a cycle and its effect on work done. Clapeyron developed Carnot s idea of the efficiency of... 

In spite of the somewhat hesitating conclusions, our aim was not perhaps to deny the possibility of exergy-based analysis at all. For instance in the case of separation processes, some information can be drawn even from a simple model, as shown above. Another problem is, how the information is further used. One should always bear in mind that the underlying ideas are rather simplistic, going back to the traditional, past-century s concepts of Carnot cycles, semipermeable membranes (in case of diffusion processes), reversible cells, and the like. Their role in the development of thermodynamics is incontestable. But in their rudimentary form, they hardly can stand as a base of contemporary engineer s reasoning, however sophisticated be the methods of computation. 

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