4. Machines consuming thermal energy

In addition to the cold source at T _F and the hot sink at T _C , these systems, which consume thermal energy, use at least a third heat source at T _M where the driving heat is supplied. These are therefore at least trithermal systems.

Note that depending on the thermal level of this third source T _M , the following two cases may be encountered:

• 1 ^er cases : T _M > T _C > T _F

• Case 2: T _C >...