Critique of some thermodynamic proofs based on the pump-engine couple
  We argue that all the common thermodynamic proofs based on the pump-engine couple possess an inherent circularity and hence are of doubtful value. In certain cases, ways of avoiding them are suggested. In others, the difficulties are discussed. Particularly, we emphasize that a neat proof of Carnot theorems requires the entropic formulation of the second law. 
Kamal Bhattacharyya