The presentation of a Lecture on optimization of refrigeration systems given during a workshop in IITD. Includes an illustration and some generic ideas.

1. Optimization in
Refrigeration Systems
P.L.Dhar
I.I.T. Delhi

2. Synopsis
The design Process
Need for Optimization
How
Energy Conservation – innovative concepts

3. The Design Process
Traditional approach
Design of a window air-conditioner
What is the basis of choosing ?
Condenser Temperature
Evaporator temperature
No. of Rows
Tube diameter

4. The Design Process
Condenser temp
Compressor Power
Consumption
Condenser size
Evaporator Tube Dia
Pressure gradient
Surface Area /
frontal area
?
Heat transfer
coefficient
?
?
Effective temp difference

5. Why Optimization ?
Increasing Competition
Increasing energy costs
Stringent energy standards
Ecological considerations
Availability of computational tools

6. Formulation of an Optimization
Problem
Three basic steps :
Objective function
Variables
Constraints
Special features of thermal system
Optimization
Nature of variables—discrete +
continuous
We may want to optimize only some
equipment NOT the whole system

8. Optimum Design of a Refrigeration
System -- problem formulation
Min TCs = FCe + FCc + RCe + RCc +Rcco
TCs= ΣNte(i) Lte Cct +Σ Ntc(i) Ltc Cct + [K Mwe PDe +
K Mwc PDc + 0.746 (BHP) ] Ckw Lh
Variables : Lte , Nte( 1,2) ; Ltc , Ntc (1,7)
No of passes, Fin design, tube layout, etc
Constraints: :
Qe = Qer
; Mwe = Mwer, Twic = Twicr ; Qc = Qcr
Max Vel of water < Vr; Tube lengths within bounds

12. Optimizing a Component
Case
Study
40 TR
DX
Chiller
Min.
initial
cost
design
SN
No of tubes
shell dia
baffle
cut
1
12 16 20 24 30 1.28 .24
32 32 32 34
2
16
16
17
21
Obj fn
pr. at
entry psi
1452 77.5
1.07 .324 998
78.7

13. Optimizing a Component
Case Study:
Condenser
coil of an AC
Min initial
cost design
Design
variable
No of Rows
No of Ckts
Tube Length
Tube O/ D
Tubes/row
Heat Transfer
Pressure Drop
Base Cost
Initial
Design
2
2
.585 m
7 mm
23
5080 W
1.0166 bar
Rs 6377
Optimize
d Design
2
3
.594 m
7 mm
21
5090 W
.8438 bar
Rs 5940

14. ECO – Design of
Refrigeration Equipment
Life cycle analysis based on emissions

15. Reducing Energy Consumption
What should be the thermostat settings of a
Window AC ?
Do we need to maintain 24oC indoors ?
Experience of Air conditioned trains .
Comfort research shows PPD for 24oC is the
same as for 27.2oC.
Impact of high outdoor temperatures and
short duration of occupancy on “optimal”
indoor temperatures

16. Reduce Energy Consumption
through Innovative Concepts
Using stratification to reduce cooling load
Window AC + Table fan
Regenerative evaporative cooling for “hotdry” climates : “Green AC”
Regenerative Evaporative cooling based cool
chests for vegetable & fruit retail outlets
Desiccant based cooling

17. Reduce Energy Consumption
through innovative concepts
Combining multiple uses -- Customized A/C
Solutions e.g. for kitchens, hostels,
restaurants
Air conditioning, cold water, hot water
Multiple indoor and outdoor unit split AC
Fuzzy Control + variable speed control for
energy saving
Variable dead-band thermostats
Personal AC

18. Reduce Energy Consumption
through innovative concepts
LPG based AC / refrigerator
Bio-mass/Bio-gas energized cold chests for
rural areas
Low cost Domestic refrigerator without
freezer
Consumer education

19. Thank you !