The Stirling cycle and Carnot’s theorem

Abstract

Carnot’s theorem is often misunderstood and not well known in its various forms. When comprehended correctly in its ‘strong form’ Carnot’s theorem precludes any other reversible cycle from matching the efficiency of a Carnot cycle when operating clockwise between the same two temperature extremes. And yet it is possible to find published references that claim a Stirling cycle has an efficiency equal to that of a Carnot cycle. This is incorrect based both on Carnot’s theorem and by actually calculating the reversible Stirling cycle’s efficiency properly.

Comment on ‘Coefficient of performance of Stirling refrigerators’

“…The present authors have shown [1] that clockwise (CW) Stirling cycles, even if reversible, have efficiencies (ε) that are strictly less than that of an ideal Carnot cycle, ε Stirling < ε Carnot . We have also published 'Not all counterclockwise thermodynamic cycles are refrigerators' [2,3], which showed that counterclockwise (CCW) Stirling cycles could not act as refrigerators.…”