ABSTRACT
We have become familiar with the Carnot cycle, which comprises two adiabatic processes and two isothermal processes (see Figure 2.6). If we assume that the working substance is a perfect gas, then the isothermal process involves no change of internal energy, and the first law tells us that Q=W for the process; thus the heat transfer for the heat added is given by
(6.1)
and the heat rejected is expressed by
(6.2)
Utilizing (2.17) and (2.29) we can derive the volume-temperature relation, viz.,
(6.3)
Thus, we observe that
(6.4)
Applying (5.30) to determine the thermal efficiency of the Carnot cycle, we find that
(6.5)
which is a very useful relation for the determination of Carnot cycle efficiency. Comparison of (5.30) and (6.5) shows that QA and QR for the Carnot cycle are related to the higher and lower temperatures (T1>T3) according to
QA=QR(T1/T3) (6.6)
consequently is useful in defining a thermodynamic temperature scale which has no dependence on thermometric properties of substances.
