00 -After a series of change, the state returns to the originalone, then the changes in its properties are '0 dz=0 3 Properties are functions of state, there exist total differential for properties 状态参数的微分特征:全微分 if z=f(x, y)then z z dz Ox www.themegallery.com Company Logo
www.themegallery.com Company Logo dz = 0 ③ Properties are functions of state, there exist total differential for properties 状态参数的微分特征：全微分 if z = f (x, y) then dy y z dx x z dz + = ▪After a series of change, the state returns to the original one, then the changes in its properties are ‘0’
Assuming =z(x, y) dz是全微分 OZ Z Total z dx t differentials OX y 充要条件: 可判断是否是 状态参数 www.themegallery.com Company Logo
www.themegallery.com Company Logo Assuming z =z (x , y) dz是全微分 y x z z dz dx dy x y = + 充要条件： 2 2 z z x y y x = 可判断是否是 状态参数 Total differentials
3. Basic State Properties 基本状态参数 Pressure p, temperature T Specific volume v can be measured directly (1) density and specific Volume 密度和比容 Density is defined as mass per unit volume 密度指单位体积所含物质的多少。 8 /m www.themegallery.com Company Logo
www.themegallery.com Company Logo Pressure p、temperature T、Specific volume v can be measured directly (1) Density and Specific Volume 密度和比容 Density is defined as mass per unit volume. 密度指单位体积所含物质的多少。 V m = 3 kg / m 3. Basic State Properties 基本状态参数
Specific volume Specific volume is the reciprocal of density and is defined as volume per unit mass 单位质量的物质所占有的体积,用V表示。 三一三 m/kg m p 比体积是表示物质内部分子疏密程度的状态参数 www.themegallery.com Company Logo
www.themegallery.com Company Logo Specific volume Specific volume is the reciprocal of density and is defined as volume per unit mass. 单位质量的物质所占有的体积，用v表示。 1 = = m V v m / kg 3 比体积是表示物质内部分子疏密程度的状态参数
(2) Pressure压力 O Definition It is defined as the force exerted by a fluid vertically on a surface of unit area 垂直作用于单位面积上的力 绝对压力 (for solid is stress: person stand on foot) ② Unit of pressure It has the unit of Newton per square meter (N/m2) 1 Pa=1 N/m2 SI Unit 1 kPa= 103 Pa 1ⅣMPa=106Pa www.themegallery.com Company Logo
www.themegallery.com Company Logo ① Definition: It is defined as the force exerted by a fluid vertically on a surface of unit area. 垂直作用于单位面积上的力 (for solid is stress: person stand on foot) ② Unit of pressure It has the unit of Newton per square meter （N/m2) 1 Pa=1 N/m2 1 kPa= 103 Pa 1 MPa= 106 Pa SI Unit (2) Pressure 压力 A F p = 绝对压力