7.2.2 Internal Energy and enthalpy(内能和焓) The energy of a given molecule is the sum of its translational, rotational, vibrational, and electronic energies.(一个给定分子 的能量是其平动动能、转动动能、振动动能和电子能的总和。) 对于由大量分子组成的给定体积的气体,所有分子所具有的能量的 总和称为气体的内能。 单位质量气体的内能称为气体的比内能。( The internal energy per unit mass of gas is defined as the specific internal energy. 用e表示
7.2.2 Internal Energy and Enthalpy (内能和焓） The energy of a given molecule is the sum of its translational, rotational, vibrational, and electronic energies. （一个给定分子 的能量是其平动动能、转动动能、振动动能和电子能的总和。） 对于由大量分子组成的给定体积的气体，所有分子所具有的能量的 总和称为气体的内能。 单位质量气体的内能称为气体的比内能。（The internal energy per unit mass of gas is defined as the specific internal energy.) 用e表示．
与比内能e相联系的另一个量为比焓h,定义为: h=e+ pv=e+ (73) 对于完全气体,e和h都只是温度的函数: (74a) h=h(t) (7.4b)
与比内能e相联系的另一个量为比焓h，定义为： p h = e + pv = e + (7.3) 对于完全气体，e和h都只是温度的函数： ( ) (7.4b) ( ) (7.4a) h h T e e T = =
de=c dt (7.5a) dh=c dt (7.5b) 定容比热 定压比热 Specific heats at constant Specific heat at constant ⅴ olume pressure
(7.5b) (7.5a) dh c dT de c dT p v = = cv －－定容比热 c p －－ 定压比热 Specific heats at constant volume Specific heat at constant pressure
7<1000K,气体为量热完全气体( calorically perfect gas), 为常数 已=C T (7.6a) h=c t (7.6b) 注意:e和h均为热状态变量( thermodynamic state variables) 它们只依赖与气体的状态而与过程无关.( they depend only on the state of the gas and are independent of any process)
T<1000Ｋ，气体为量热完全气体（calorically perfect gas ), cv 、 c p 为常数 (7.6b) (7.6a) h c T e c T p v = = 注意：e和h均为热状态变量（thermodynamic state variables ), 它们只依赖与气体的状态而与过程无关．（they depend only on the state of the gas and are independent of any process)
T (7.6a) h=c T (7.6b) (76b)-(76a) C R (7.7) 定义比热比 y R I R (78) R (7.10) y y
(7.6b) (7.6a) h c T e c T p v = = (7.6b)-(7.6a): c p − cv = R (7.7) 定义比热比 v p c c = 1 (7.8) p p v c R c c − = 1 1 p c R − = −1 = R c p −1 = R cv (7.９) (7.１０)