Carnot Revisited From Ideal to Real Processes

2 Carnot Revisited From Ideal to Real Processes 

We recall that the maximum amount of work available in a heat flow Q of a constant temperature TH T0 is given by 

The higher Qin and Q0, the higher the required and associated temperature differences for heat transfer into the working fluid at high temperatures and out from the working fluid at low temperatures for heat exchangers with finite heat exchange area. If the assumption is made that these two losses 

For a proof of this result, we refer to the original papers [1,2], but we can make the existence of these two optimal temperatures plausible by the following reasoning. Suppose we wish to introduce heat into the Carnot engine with a rate Qin- This fixes the upper temperature Thc of the Carnot cycle, for example by the approximate relation 

It is obvious from Equation 5.9 that by fixing Qin, THC is fixed and that according to Equation 5.11 this fixes Toc. The power of the engine is then given by 

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