1. ENERGY ANALYSIS GROUP THREE THERMODYNAMICS SHARAFATU BADARU
UGWU CHINYERE
AUGUSTINE EMEKA EKENE
INNOCENT

2. Energy Balance
Concerned with energy changes and energy flow in a chemical process.
Conservation of energy – first law of thermodynamics i.e. accumulation of energy in a system = energy input – energy output

3. Energy balance W
system
mass out
mass in
Hin
Hout Q

4. Uses Heat required for a process Rate of heat removal from a process
Heat transfer/design of heat exchangers
Process design to determine energy requirements of a process
Pump power requirements (mechanical energy balance)
Pattern of energy usage in operation
Process control
Process design & development
etc

5. Energy balance techniques
Complete mass balance/molar balance
Calculate all enthalpy changes between process conditions and standard/reference conditions for all components at start (input) and finish (output).
Consider any additional enthalpy changes
Solve enthalpy balance equation

6. Laws of Thermodynamics and Energy Balance
Energy cannot be created nor destroyed but can change from one form to another
therefore energy accumulation =input-output
Kinetic→ Motion → 1/2mv2
Potential → Position → mgh
Internal→ Due to molecular interaction
Q heat ∆T- between system + surrounding energy transfer as a result of temp difference Q - + when transfer to system from surrounding
w- work is response to driving force
W is +ve when done on the system by the surrounding
–ve when system does work on surrounding
Enthalpy is a relation for U +PV

7. For a closed system

8. Energy balance for an open system

9. For an open system

10. CLOSED AND OPEN SYSTEM
Open-mass crosses the boundary Closed-mass does crosses the boundary Closed ∆U + ∆Ep + ∆Ek = Q-W + Q= heat transfer to system W= work done on system no acceleration ∆E No change in height ∆Ep System T= surrounding T, insulated →Q=O adiabatic no moving parts, electric current or radiation at the boundry, then w=o

11. CLOSED AND OPEN SYSTEM contd
Open ∆H + ∆Ep + ∆Ek= Q-W
(per unit time)
∆H→Hfinal – Hinitial
Q,W- depends on boundary
Consider a cylinder with a movable piston moves slowly to compress the gas Neglecting ∆Ep,
what is the energy balanced?
(closed system)
Q-W = ∆U
Isothermally Q=W
Adiabatic Q=O ∆U=-W

12. Thank you for listening
References
The Properties of Gases and Liquids, R. Reid
Elementary Principles of Chemical Processes, R.M.Felder and R.W.Rousseau
Thank you for listening