热力学第二定律的量化表述及其应用例

Quantifiable Expression of The Second Law of Thermodynamics and It's Application

尝试对热力学第二定律进行量化表述,通过能量在转移过程中有效能量变化的计算,当消耗的有效能变为无效能时,则用于描述不可逆过程;当有效能与功等量交换时,则用于描述可逆过程,并给出了多过程系统的第二定律计算式;介绍了有效能函数与热力学的三个能函数U、H、F的关系及其微分关系;给出了传热、摩擦、节流、冷热液体混合等7种不可逆过程和等价内可逆卡诺循环热机的有效能消耗。用有效能消耗量与输运热量的比值,定义了不可逆传热过程的有效能消耗系数η_(u,ir);用有效能转化功量与吸热量的比值定义的热机效率叩,发现传热过程的有效能消耗系数和卡诺循环热机的效率有相同的表达式,为η_(u,ir)=η=T_0(1-T_2/T_1)/T_2,不仅与热源高、低温T_1和T_2有关,还与环境温度T_0有关。

This paper attempts to give a quantifiable expression of the second law of thermodynamics through calculating the available energy changes in energy transfer processes.It can used to describe an irreversible process while consumed available energy changes to unavailable energy,and can be used to describe a reversible process while consumed available energy changes to equal amounts of power.This second law calculating formula is also suitable for multi-process systems.The available energy function is introduced,and it’s relation and differential relation with Three thermodynamics energy functions（U,H,F） are described.Available energy consumptions are given in the equivalent endoreversible Carnot cycle heat engine and several irreversible processes,such as heat transfer,friction,throttling,mixing of liquids with different temperatures,etc.The available energy consumption coefficient —ηu,ir,is defined as the ratio of the available energy consumption rate to the heat transport rate.And the heat engine efficiency —η,is defined as the ratio of the available energy amounts which changes to power to the heat absorption amount It is found that the calculating formulae of the available energy consumption coefficient in a heat transfer process,ηu,ir=η = T0（1 — T2/T1）/T2,is same with the calculating formulae of the Carnot cycle heat engine efficiency.It has relation not only with the high temperature T1,and low temperature T2,of heat source,but also with the environment temperature T0.