Is there a link between the macroscopic approach to irreversibility and microscopic behaviour of the systems? Consumption of free energy keeps the system away from a stable equilibrium. Entropy generation results from the redistribution of energy, momentum, mass and charge. This concept represents the essence of the thermodynamic approach to irreversibility. Irreversibility is the result of the interaction between systems and their environment. The aim of this paper is to determine lost works in a molecular engine and compare results with macro (classical) heat engines. Firstly, irreversible thermodynamics are reviewed for macro and molecular cycles. Secondly, irreversible thermodynamics approaches are applied for a quantum heat engine with -1/2 spin system. Finally, lost works are determined for considered system and results show that macro and molecular heat engines obey same limitations. Moreover, a quantum thermodynamic approach is suggested in order to explain the results previously obtained from an atomic viewpoint.

宏观的不可逆方法与系统的微观行为之间是否存在联系？自由能量的消耗使系统远离稳定的平衡。熵的产生来自能量，动量，质量和电荷的重新分布。这个概念代表了不可逆热力学方法的本质。不可逆性是系统与其环境之间相互作用的结果。本文的目的是确定分子发动机中的损失功，并将结果与​​宏观（经典）热机进行比较。首先，对宏观和分子循环的不可逆热力学进行了综述。其次，不可逆热力学方法被应用于具有-1/2自旋系统的量子热机。最后，确定了所考虑系统的损失工作，结果表明，宏观和分子热机都遵循相同的限制。此外，提出了一种量子热力学方法，以解释先前从原子观点获得的结果。