This preview shows pages 1–7. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: In two circumstances ) ( = ∂ ∂ dV V U T Will be true 1. Constant volume 2. U is independent on V. This is exactly true for ideal gases and incompressible fluids and approximately true for low pressure gases The equation should meet the following requirements: mechanically reversible, constantvolume process, closedsystem, both ∆ E P and ∆ E K are negligible and Ws =0 ∫ = ∆ = 2 1 T T V dT C U Q For Chapter 4. Heat Effects In two circumstances ) ( = ∂ ∂ dP P H T will be true 1. Constant pressure process 2. H is independent on P. This is exactly true for ideal gases approximately true for low pressure gases ∫ = ∆ = 2 1 T T P dT C H Q For The equation should meet the following requirements: mechanically reversible, constantvolume process, closedsystem, both ∆ E P and ∆ E K are negligible and W s =0 We need relation of C with T, i.e. C = f (T). A popular empirical equation: C P /R is dimensionless so C P has the same unit as R The real gas becomes ideal in limit as P → 0. If it remains ideal when compressed to a finite pressure, it would be hypothetical ideal gas. For this type of gases, C p ig and C V ig are therefore different for different gases (being affected by their chemical natures) Table C.1 gives the constants A, B, C, and D for different gases in the idealgas state For ideal gases, w e have known from Eq (3.19) This means that C V and C P follow the same trend with T The molar heat capacity of the mixture in the idealgas state: For liquid and solid, dependences of C P and C V on temperature are found by experiments. Table C.2 and C.3 give some C P , C V , A, B, C and D data. ( 29 2 2 2 2 2 ) 1 ( 3 ) 1 ( 2 ) ( T T T D T C T B A dT DT CT BT A dT R C T T T T P + + + + + + = + + + = ∫ ∫ τ τ τ τ T T ≡ τ These equations can be used to evaluate H P C With 2 2 2 ) 1 ( 3 ) 1 ( 2 T D T C T B A R C H P τ τ τ τ + + + + + + = A starting estimated T allows evaluation of H P C of this value to (4.10), obtaining a new T, go (4.8) again, etcof this value to (4....
View
Full
Document
This note was uploaded on 05/01/2011 for the course CHBE 2110 taught by Professor Gallivan during the Spring '08 term at Georgia Institute of Technology.
 Spring '08
 Gallivan

Click to edit the document details