大学化工专业英语Lesson-3The Second Law of Thermodynamics热力学第二定律Thermodynamics is concerned with transformation of energy, and the laws of thermodynamics describe the bounds within which these transformation are observed to occur.热力学讨论的是能量的转换，热力学定律描述了这些转变能够发生的边界条件。
The first law, stating that energy must be conserved in all ordinary processes, has been the underlying principle of the preceding chapters.第一定律指出了在一般过程中，能量是守恒的，它是前面章节遵循的根本原则。
The first law imposes no restriction on the direction of energy transformation.第一定律对能量转换的方向性没有限制。
Yet, all our experience indicates the existence of such a restriction.然而，我们的经验表明这种限制的存在。
To complete the foundation for the science of thermodynamics, it is necessary to formulate this second limitation. Its concise statement constitutes the second law. 为了完善热力学的科学基础，有必要规定第二个限制条件，它简洁的内容构成了第二定律。
The differences between the two forms of energy, heat and work, provide some insight into the second law.两种形式的能量：热和功之间的不同，为第二定律提供了一些见解。
These differences are not implied by the first law.这些不同是第一定律中没有提到的。
In an energy balance both work and heat are included as simple additive terms, implying that one unit of heat, such as a joule or BTU, is equivalent to the same unit of work.在能量平衡中，功和热作为简单的加和项，表明了，一个单位的热，如1J或1BTU，等于相同单位的功。
Although this is true with respect to an energy balance.虽然这是真正的能量平衡。
Experience teaches that there is a difference in quality between heat and work.经验告诉我们，热和功之间有一个质量的差异。
This experience can be summarized by the following facts.这方面的经验可以从以下事实中总结出来。
First, the efficiency of the transformation from one form of work to another such as electrical to mechanical as accomplished in an electric motor, can be made to approach 100 percent as closely as is desired.首先，使得从一种形式的功向另一种形式的功的转换效率尽可能的接近于我们所向往的100%，比如，从电能到机械能的转换能够通过电动机来实现。
One needs merely to exert more and more care in eliminating irreversibilities in the apparatus.我们仅仅需要越来越关心装置设备中不可逆性的消除。
On the other hand, efforts to convert energy transferred to a system as heat into any of the forms of work show this regardless of improvements in the machines employed.另一方面，将转移到系统中的热量转换成任何一种形式的功表明，这与所使用机器的改进无关。
The conversion is limited to low values（40 percent is an approximate maximum）.这种转换率是被限制在一个较小的值内（40%大约是最大值）。
These efficiencies are so low, in comparison with these obtained for the transformation of work from form to another, that there can be no escape from the conclusion that there is an intrinsic difference between heat and work, in the reverse direction, the conversion of work into heat with 100 percent efficiency is very common.与不同形式的功之间转换的效率相比，这些效率是太低了，以至于得出一个不可逃避的结论：热与功之间有一个本质的不同，在相反的方向上，功向热转换的效率为100%，这是非常普通的。
Indeed, efforts are made in nearly every machine to eliminate this conversion, which decrease efficiency of operation.事实上，为了消除这种转变，我们在努力改进几乎每台机器，这降低了操作效率。
These facts lead to the conclusion that heat is a less versatile or more degraded form of energy than work.从这些事实中可以得出一个结论，热与功相比，没有那么多变，没有更多能量的退化形式。
Work might be termed energy of a higher quality than heat.功可以被称为是比热具有更高质量的能量。
To draw further upon our experience, we know that heat always flows from a higher temperature level to a lower one, and never in the reverse direction.为了进一步的总结我们的经验，我们知道从高温到低温将会产生热量，然而在相反的方向上不会有热量产生。
This suggests that heat itself may be assigned a characteristic quality as well as quantity, and that this quality depends upon temperature, the relation of temperature to the quality of heat is evident from the increased in efficiency with which heat may be converted into work as the temperature of the source is raised.这表明，热本身可能被分配了一定的质量和数量，这个质量取决于温度，从增加的效率来看，温度和热的质量的关系是明显的：在这样的效率下，随着原始材料温度的升高，热能够转化成功。
For example, the efficiency, or work output per unit of fuel burned, of a stationary power plant increases as the temperature of the steam in the boiler and superheater rises.例如，一个固定式发电站的效率，或者燃烧每单位燃料的输出功，随着锅炉或过热器中蒸汽温度的升高而增加。
Statements of the Second Law第二定律的陈述The observations just described are results of the restriction imposed by the second law on the direction of actual processes. Many general statements may be made which described this restriction and hence, serve as statements of the second law. Two of the most common are:刚刚描述的观察结果是第二定律对实际过程在方向上的限制的结果。
许多通用的语句能够描述这个限制，因此，这些描述可以作为第二定律的陈述。
最常见的两个是：1. No apparatus can operate in such a way that its only effect（in system and surroundings）is to convert heat absorbed by a system completely into work.1. 没有设备能够仅仅产生这样一种影响：实现将系统吸收的热量全部转化成功。
2. Any process which consists solely in the transfer of heat from one temperature to a higher one is impossible.任何一个从低温到高温的过程仅仅包含热量的转移是不可能的。