Engineering and Chemical Thermodynamics (Koretsky) Chapter 2 Summary

Chapter 2
First Law of Thermodynamics

V 2 : (m/s2)
Euniv  0
m: (kg)

Esystem  Esurroundings  0 E: (J)
g: (m/s2)
∆𝐸 = ∆𝐸𝑘 + ∆𝐸𝑝 = 0 z: (m)

1 2
EK  mV EP  mgz
2
Work (W)
W: (J)
W   FE dx
w: (J/mol)
FE
W  d ( Ax )   PE dV
Dependent of parh
A

w   PE dv

Heat (Q)
𝑄 = 𝑛∆ℎ Q: (J)
Sign convention:




Reversible process:
A process is reversible if, after the process occurs, the system can be returned to its
original state without any net effect on the surroundings.
Amount of reversibility: Amount of reversibility for compression:
wirrev wrev
exp  comp 
wrev wirrev


1

, wrev (exp) = - wrev (comp)
First law of thermodynamics for closed systems:
∆𝑈 = 𝑄 + 𝑊 ∆𝑈: (J)
∆𝑢 = 𝑞 + 𝑤 ∆𝑢: (J/mol)
First law of thermodynamics for open systems:
Flow work: 
W 
flow in   Pin Ain
dx
dt
 Pin AinVin  Pin nin vin



w
W 
    Pin vin
flow in
flow in
nin

W  flow out   Poutnoutvout


W  W shaft  W flow  W s   nin Pv in   nout  Pv out
in out

Energy balance for open systems:




If kinetic and potential energies can be neglected:

0   nin hin  nouthout  Q  W S
in out
2