基于焓守恒的热力学第一定律及其数学表达式的修正

Investigation of the First Law of Thermodynamics and Its Mathematical Expressions

基于能量守恒定律探讨了热力学体系存在的和过程中出现的能量形式,研究了过程中能量形式的转换和守恒规律。揭示出体系的总能量是焓,而基于内能守恒推导的热力学第一定律方程式不能表述过程以非等温路径发生时的能量守恒。活塞型热机热-功转换过程以非等温路径发生时,还存在体系和环境之间传递的第三种能量形式。这一形式的能量没有做功而伴随位移功离开体系。基于焓守恒提出了新的热力学第一定律第一方程式,新方程式包括了这部分能量。把热-焓转换过程、活塞型热机热-功转换过程和涡轮型热机热-功转换过程归类为基本热力学过程,提出用3个热力学第一定律方程式分别表述3种热力学过程的能量守恒规律,还给出了过程中热与功的关系。

Based on the law of conservation of energy,the energy forms existing in the thermodynamic system and appearing in the process are discussed,and the conversions of energy forms and conservation of energy in the process are studied.It is revealed that the total energy of the system is enthalpy,and the equation of the first law of thermodynamics derived from the conservation of internal energy cannot describe the conservation of energy when the process occurs in a non-isothermal path.When the heat-work conversion process of the piston-type heat engine occurs in a non-isothermal path,there is a third form of energy transferred between the system and the surroundings.Termed as lost enthalpy,this form of energy leaves the system together with displacement work instead of doing work.Based on the conservation of enthalpy,a novel equation of the first law of thermodynamics is presented,and the novel equation includes the lost enthalpy.The heat-enthalpy,the piston-type heat-work and the turbine-type heat-work conversion processes are classified as basic thermodynamic processes,and meanwhile three equations of the first law of thermodynamics are presented to describe the energy conservation of these three thermodynamic processes respectively.The relationship between heat and work in the process is also given.