Comment on 'Economies of scale: The physics basis' [J. Appl. Phys. 121, 044907 (2017)]

A recent article [A. Bejan, A. Almerbati, and S. Lorente, J. Appl. Phys. 121, 044907 (2017)] takes note of a relationship between size and efficiency that appears in the performance data of many engines and power plants. The authors attempt to interpret this phenomenon thermodynamically, concluding that the relationship is predicted by a general thermal power plant model. However, this conclusion is the result of an elementary error. The efficiency of the idealized thermal model in fact stays constant or decreases with increasing size.