1. Lecture Objectives:
Start energy production systems
- Sorption cooling

2. Absorption Cycle Same as vapor compression but NO COMPRESSOR
Replace compressor

3. Absorption cooling cycle
Rich solution of
Heat
H2O
H2O + NH3
Rich solution of
H2O
H2O + NH3

4. Mixtures (T-x diagram)
Dew point curve
Saturated vapor
Mixture of liquid and vapor
Saturated liquid
Bubble point curve
For P= 4 bar

5. h-x diagram hfg hfg Isotherms are shown only in liquid region for H2O
for NH3
Isotherms are
shown only
in liquid region

6. Composition of h-x diagram
Saturated vapor line at p1
Equilibrium construction line at p1 1e
Used to determine
isotherm line in
mixing region!
Start from x1;
move up to equilibrium
construction line;
move right to saturated
vapor line; determine 1’;
connect 1 and 1’.
Isotherm at P1 and T1
Adding energy B A x1
X1’
mass fraction of ammonia in saturated vapor

7. h-x diagram at the end of your textbook you will find these diagrams for 1) NH3-H2O 2) H2O-LiBr
LiBr is one of the
major liquid descants
in air-conditioning
systems

8. Adiabatic mixing in h-x diagram (Water – Ammonia)
From the textbook (Thermal Environmental Eng.; Kuehen et al)

9. Absorption cooling cycle
Rich solution of
Heat
H2O
H2O + NH3
Rich solution of
H2O
H2O + NH3

10. Mixing of two streams with heat rejection (Absorber)
mixture of
H2O and NH3 m2 m3
=pure NH3 (x2=1) m1 m3 m2
Not the isotherm ! m1 2 Q
cooling
Heat rejection
Mixture of 1 and 2 3’
Mass and energy balance:
(1)
(2) 1 3
(3) x3 x
From mixture equation:
Substitute into (2)
Substitute into (3)
From adiabatic mixing
(from previous slide)

11. Change of pressure (pump)
Sub cooled
liquid at p2 2
Saturated
liquid
at p1 1 p1
≠p2
Very small ∆h1-2
(insignificant) m1
=m2 p2
Saturated liquid at x1
=x2 2 p1
Saturated liquid at 1
x1=x2

12. Heat transfer with separation into liquid and vapor (Generator)
Saturated
vapor
Heat
=2V
Sub cooled
liquid
Saturated
liquid
Isotherm
We can “break”
this generator
into 2 units
heating m4
Q12 /m1
2L= m1
=m2
Separator
sub cooled
liquid
mixture x1
Q12 m3
Apply mass and energy
balance In the separator :
Apply mass and energy
balance In the heat exchanger
defines
point 2
in graph
Defines points 3 and 4 in graph

13. Heat rejection with separation into liquid and vapor (Condenser)
Saturated
vapor at p1 m1
Saturated
vapor 1
heat
rejection m2
Q1-2/m1 m1
=m2
Saturated
liquid at p1 x1
=x2 2 p1
=p2
x1=x2

14. Throttling process (Expansion valve)
Saturated vapor 1 2V
Isotherm 2 h1
=h2 T1 1 2 p1
Saturated liquid at p1
≠p2 T2 2L
Saturated
liquid m1
=m2 p1
≠p2 p2
Saturated liquid at x1
=x2 x1
=x2

15. Simple absorption system3V 3L
3LLP

16. Simple absorption system
Saturated vapor at p2=p3=p4 3V 6 3 5V
mixing 1’
Needed
thermal
energy
Useful
cooling
energy 3L 4
3LLP 5 2
Saturated liquid at p2=p3=p4 1 5L
Saturated liquid at p1=p5=p6=p3_LLP

17. Heat transfer with separation into liquid and vapor (Generator)
How to move
point 4 to right ?
=2V
=2V
heating m4
Q12 /m1
2L=
2L=
=m2 m1
=m2
mixture
Separator
sub cooled
liquid
mixture x1 x1
Q12 m3
Q12 m3

18. Heat rejection with separation into liquid and vapor (Enrichment NH3 in the vapor mixture)
This is our point
cooling 1
4=2V
Separator
6=5V
Q12 /m1
cooling
Q45 /m4 x8 m8 8 7 m1
=m2 5 2
sub cooled
liquid
mixture
isotherm m3 2L
Q12 x1 x8

19. Heat rejection with separation into liquid and vapor (Enrichment NH3 in the vapor mixture)
This is our point
cooling 1
4=2V
Separator
6=5V
Q12 /m1
cooling
Q45 /m4 x8 m8 8 7 m1
=m2 5 2
sub cooled
liquid
mixture
isotherm m3 2L
Q12 x1 x8

20. Ammonia Vapor Enrichment Process (Rectification)

21. Absorption cooling with preheater System improvement #1
Rich ammonia vapor 4 5
Refrigeration and air conditioning (Ramesh et al)

22. Absorption cooling with preheater
Saturated vapor at p1’
1’’’V=3
Major heat
source 6
1’’’
mixing
isotherm 6h
1’’
Useful
cooling
energy
1’’’L =2 4 5 1’
Saturated liquid at p1’
2’ , 2’’ 1
Saturated liquid at p1
Cooling
tower
Pumping
energy
COP= Q cooling / Q heating (Pump ???)

23. For Real energy analysis you need real h-x diagram!
hfg
for H2O
hfg
for NH3
For Real energy analysis you need real h-x diagram!

24. Use of precooling (system improvement #2)

25. Absorption cooling with precooling
Saturated vapor at p1’
1’’’V=3
Major heat
source 6’ 6 6h
1’’’
mixing
Saturated liquid at p1’
isotherm
1’’
Useful
cooling
energy
(larger!)
1’’’L =2 4 1’
Saturated liquid at p1
2’ , 2’’ 4’ 5 1
Cooling
tower
(needs to cool more!)
Pumping
energy

26. System improvement #3 (described as Rectification)
Generator with Enrichment of NH3
Different 8V 9 8L 10
8LLP 11

27. Heat rejection with separation into liquid and vapor (Enrichment NH3 in the vapor mixture)
This is our point
cooling 1
4=2V
Separator
6=5V
Q12 /m1
cooling
Q45 /m4 x8 m8 8 7 m1
=m2 5 2
sub cooled
liquid
mixture
isotherm m3 2L
Q12 x1 x8

28. Absorption system with Enrichment (no preheater nor precooler)
Saturated vapor at p2 3V 8V 3
mixing 11 8L 1’
Useful
cooling
energy
8LLP 10 3L 2 9
Saturated liquid at p2 1
Saturated liquid at p1