Figure 2.

The maximum-work efficiency η ^mw or the CA efficiency η _CA as a function of the Carnot efficiency η _C. The approximate and exact results of the optimal efficiency, ${\eta }_{\mathrm{ap}}^{m\mathrm{w}}$ and ${\eta }_{\mathrm{ex}}^{m\mathrm{w}}$ are denoted by a blue dashed line and a red solid line, respectively, while the CA efficiency η _CA is represented by a black dotted line. Here the parameters are N = 100, α = 3, γ = −3, and $r_1=r_2=r_3=1$.