The discussion revolves around the feasibility of achieving Carnot efficiency in real-world engines, specifically comparing the Carnot cycle and the Stirling cycle. Participants explore the implications of reversibility, thermodynamic principles, and the limitations of real-world applications.
Participants express differing views on the relationship between reversibility and efficiency, particularly regarding the Stirling cycle. There is no consensus on whether the Stirling cycle can achieve Carnot efficiency, and the discussion remains unresolved.
Limitations include varying interpretations of reversibility in thermodynamic cycles and the specific conditions under which efficiency can be measured. The discussion reflects differing understandings of the principles governing ideal and real-world engines.
The thermodynamic inefficiency of the Carnot cycle is NOT due to friction. It has nothing to do with friction and everything to do with the second law of thermodynamics.kntsy said:I think it is due to friction and the carnot efficiency is derived in a reversible cycle.Also,can i build just a little bit irreversible but still carnot? But if irreversible how can i draw the graph? Still smooth line?
Andrew Mason said:The thermodynamic inefficiency of the Carnot cycle is NOT due to friction. It has nothing to do with friction and everything to do with the second law of thermodynamics.
The Carnot cycle is an ideal. It represents the theoretical limit of thermodynamic efficency. It can be approached but never reached in the real world.
AM
kntsy said:If i use a stirling cycle in a reversible process, can the efficiency reach (1-T2/T1)? It is reversible so can?
A Stirling cycle is not reversible. You cannot simply make any cycle reversible. The Carnot cycle is reversible because heat flows into and out of the engine with the engine and reservoirs at the virtually the same temperature (in infinitessimally small difference in temperature). Since the temperature of the reservoir and system gas are the same, the change in entropy of the reservoir is equal and opposite to that of the engine (sum of entropy changes = 0). The other parts of the cycle are quasistatic adiabatic processes which could be reversed with an infinitessimal change in pressures (since they are adiabatic, dQ = 0 -> dS = dQ/T = 0). So there is no change in entropy of the system and surroundings during the Carnot cycle.kntsy said:So a reversible stirling cycle is always less efficient to carnot efficiency? BOOK says ANY reversible cycle can reach carnot effieciency! Is the BOOK wrong?