13车辆-热工学-3-temperature pressure.pdfVIP

Problem Deduce the crude oil price and compare it with the price of domestic gasoline. Is it cheaper in domestic market than international market or vice verse? Crude oil price is 91.67 dollar per barrel by WTI. 1 barrel = 42 gallon 1 gallon = 3.7854 L The product ratio of gasoline to crude oil is 5:6. ( ) 1 International price of gasoline: 91.67 6.145 / (42 3.7854)× × × 5/6 = 4.25 Example h i ld d llT e pr ce of go was 1248.1 o ar per ounce. How much is it in RMB per gram? 1 ounce = 28.3 g 1 lbm =16 ounce 1 dollar = 6.145 yuan 1248.1 6.145 / 28.3× = 270.5 270.5 yuan per gram 2 1.4 Properties of a System 7 important properties for thermodynamic purposes: property symbol Pressure P temperature T (page12) mass m specific volume v specific internal energy u ifi th l hspec c en a py specific entropy s 3 4 Intensive property Extensive property Intensive property i d d t f th f th t— are n epen en o e mass o e sys em. E.g. — temperature，pressure, density(ρ), etc Extensive property — depends on the size or extent of the system. E.g. — mass, volume(V), etc 5 Intensive property Extensive property Specific property– per unit mass extensive property. Specific property is an intensive properties. specific volume, ν=V/m specific internal energy, u=U/m Extensive property Intensive property internal energy U specific internal energy u volume V specific volume v enthalpy H specific enthalpy h entropy S specific entropy s 6 Basic test for ex- intensive properties Divide the system to two equal parts with an imaginary partition, the value of a property remains the same, it i i t i t s n ens ve proper y. If the value changed to the half of previous it is , extensive property. 7(page12) Continuum– Matter is viewed as continuous and homogenous with no holes. The continuum idealization is valid as long as h i f h i l l i ht e s ze o t e system s arge re at ve to t e space between the molecules. Note: In this text we will limit ou