OWAIS NOORUDDIN
Åbo Akademi
Supervisor Prof. Henrik Saxen
Optimization of refrigeration
process
Problem Description
• To optimize the cooling system of 2 MW
• Free cooling. Is it enough?
• Free cooling alongwith vapor compression
cycle.
• Mix integer non linear optimization of cooling
system for the whole year run.
1
Process Integration
HE-1
Hot
stream
HE-2
HE-3
HE-4
Vapor
Compression
Cycle
Storage
Tank
2
Free Cooling Finned Tube heat
Exchanger
Figure1: Heat Exchanger (Finned Tube)
3
Ideal Vapor Compression Cycle
Figure 2A: Vapor compression cycle
Figure 2B: Ideal Vapor Compression
Cycle
COP = Coeffecient of performance
COP(refrigeration)= Heat absorbed/Work supplied
=m(ref)*(H1-H4)/Win
COP(Heat pump)
= Heat out/Work supplied
= m(ref)*(H2-H3)/Win
.
4
Real Vapor Compression Cycle
Figure 2D: Vapor compression Cycle with subcooling and superheating
• With sub cooling of the liquid, refrigerating effect and COP increases without increasing the work
requirement but for superheating COP may increase, decrease or remain unchanged . It depend on the
range of pressure of the cycle.
• Decrease in inlet pressure decreases the refrigeration effect and increases the work of compression. The
effects of these two lead to decrease the COP while increase in discharge pressure required more work from
compressor and decline in COP.
5
Process Flow Diagram
Figure 3: Flow sheet
6
Problem Solution
• Sequential Method (by using Fmincon in
Matlab environment)
• Equation based
-(By using Gams with Mixed Integer Non
Linear Programming)
-(By using Aspen Plus, only simulation of the
selected cases without optimization)
7
Future Plan
• To study the cooling storage tank with air heat
exchanger.
• To study the complex heat exchanger network
system for the improvement in integration by
varying size and optimizing cost of the
process.
• Multiobjective optimization.
8
Refrences
Figure 1 http://www.pemco.fi/09/ilmalauhduttimet/v-malliset-tekninen-tieto
Figure 2A and 2B Thermodynamic Engineerig approach, Younus A, Cengel,
5th edition chapter 11.
Figure 2C http://engr.bd.psu.edu/davej/classes/thermo/chapter7.html
Figure 2D http://www.alephzero.co.uk/ref/circeff.htm
9
Thank you
for your attention