Chem. Eng. Thermodynamics (TKK-2137) 14/15 Semester 3 Instructor: Rama Oktavian Office Hr.: M.13-15, Tu , W , Th , F

Outlines 1. 1 st law thermodynamics 2. Energy balance for closed system 3. The phase rule 4. Energy balance for open system

1 st law thermodynamics  Properties of matters: – Energy content of matters: – Other properties having the same unit as energy  Enthalpy, Free energy, etc. Kinetic Energy Internal Energy Potential Energy NOTE: Heat and Work are energies exchanged between a system and its surrounding, not properties associated with matters. Total Energy of matters

1 st law Thermodynamic Work (W) Work can be followed by volume change of fluid (ex. Compression of a gas by a piston) Total volume gives total work Work per unit mass or mole W+ (-) shows that fluid compression is positive work

1 st law Thermodynamic Heat (Q) -Heat moves from object with higher T to object with lower T -Temperature difference is driving force of heat flow W & Q are path variables Path variables only have meaning when exchange between a system/substance and surroundings A substance does not contain a certain amount of work or heat

1 st law thermodynamics Kinetic Energy(E k ) We will focus on 5 forms of energy Potential Energy(E p ) Internal Energy(U) Question: what is the relationship between the various forms of energy?

1 st law Thermodynamic Total energy is constant  Ek,  Ep,  U Q W -  E(surrounding)  E(system)  E(system) +  E(surrounding) = 0 ＋ + Mathematical formula

1 st law Thermodynamic Closed system closed when no mass passes the boundary Thus: 1 st law thermodynamic for closed system:

1 st law Thermodynamic Closed system : state variable : path variables P T P 1,T 1 P 2,T 2 For closed system Change from state 1 to state 2 with 2 different paths What is the value for Q & W for each paths ?

1 st law Thermodynamic Closed system

1 st law Thermodynamic Reversible process No-friction No turbulence Always in equilibrium Valid only for reversible proses Reversible work is ideal work 1 st law:

1 st law Thermodynamic Constant volume process Therefore Heat transferred from or to system is equal with the value of internal energy change

1 st law Thermodynamic Enthalpy Heat transferred from or to system is equal with the value of enthalpy change Constant pressure process:

1 st law Thermodynamic Heat capacity Constant-V process: For constant P process For constant V process State variable Constant-P process:

1 st law Thermodynamic Rework Example 2.9 Example 2.10

The phase rule Gibbs phase rule where: F = degree of freedom The number of maximum variables that must be specified or fixed to determine the other variables  = number of phase Phase = a homogeneous region of matter N = number of component For pure substance (N = 1), minimum F = 0

The phase rule Gibbs phase rule

Energy balance for open system Open system system  E(system) +  E(surrounding) = 0 1 st law: Every unit of mass contains energy: Total energy :

Energy balance for open system Open system Total energy in the system can change due to accumulation or loss: Therefore: (influent)(effluent)

Energy balance for open system Work: can be generated by flow work in and out (W f ) and shaft work (W s ) influent effluent Remember:

Energy balance for open system 1 st law thermodynamic for open system effluentinfluent General process: Steady state: One inlet and outlet: Rate of energy Rate of energy per mass or mole

1 st law Thermodynamic for open system Rework Example 2.15 Example 2.16