A mechanical model for exergy assessment: analogy with the equilibrium of a lever

We propose an analogy between the laws of thermodynamics and the well-known laws of]ever balance in mechanics. That is made possible thanks to the exe rgetic approach. The energies received or lost by the system are regarded a s forces, the corresponding Carnot factors to lever arms. We use the entrop ic temperature concept to define Carnot factors in the case of mass flows. The equilibrium of the lever with out friction corresponds to a reversible transformation. The equilibrium with friction in the axis to an irreversibl e one. The irreversibilities in the system are characterized using two para meters: the transfer exergy efficiency and the conversion exergy efficiency . (C) 2001 Editions scientifiques et medicales Elsevier SAS.