变重力场中理想气体的“P—V”循环及熵变

在恒定的重力场中密闭于刚性容器中的理想气体在垂直方向上的压缩和膨胀构成“压力一体积”（P-V）循环，利用此循环可实现“热一功”转化，但气体必须工作在两个不同温度的热源之间。由于重力场中刚性容器中的气体的压力分布随重力的变化而变化，因此可通过增、减重力加速度使密闭容器中气体压力改变构成P—V循环，通过此循环也可实现“热-功”转化，此类“热-功”转化的循环有别于传统的卡诺循环。变重力场中理想气体的P—v循环导致的“热-功”转化不需要两个不同温度的热源。本文的计算表明在可逆过程中此P—V循环的熵变量不符合热力学第二定律，深刻地揭示了热力学第二定律的局限性。

The Pressure-Volume Cycle of Ideal Gas within Alternating Gravitational Field and Entropy Reduction

In gravitational field of constant, the vertically expanding and compressing of the gas can create Camot-efficiency Cycle to convert heat energy into mechanical one. However the working substance must cycle between two heat reservoirs（source） of different temperature. Due to the fact that the gas pressure varies with the gravitational acceleration a P-V cyclic process can also be created by repeated alteration of the gravitational field. Such gravitational cyclic process can also convert heat energy into mechanical one. In contrary to the Carnot-efficiency Cycle, in such process the working substance not have to cycle between two heat reservoirs（source） of different temperature. Because the etticiency formula applied in Carnot Cycle can not be directly used to this cycle, the efficiency of this gravitational cycle must be calculated with a different way. With the reversible process of ideal gas a verdict failing to follow the Carnot theorem is educed in this article. The analysis by the author reveals that the second law of thermodynamics are not universal.