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

2. Desiccant Systems: Reading assignment

3. Desiccant wheel

4. Desiccant wheel
Figure 3 – A desiccant-based cooling system combined with regenerative heat exchanger, vapor compression cooling, and evaporative humidifier (hybrid system).

5. Variation in Cycles
Much more in the paper I gave you (Technical development of rotary
desiccant dehumidification and air conditioning)

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

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

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

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

10. 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

11. 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

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

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

14. Mixing of two streams with heat rejection (Absorber)
mixture of
H2O and NH3 m2 m3
=pure NH3 (x2=1) m1 m3 m2 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)

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. Simple absorption system
Generator with of Enrichment NH3
Different 8V 9 8L 10
8LLP 11

20. Absorption system with
Saturated vapor at p2=p3=p4 3V 8V 3
mixing 11 8L 1’
Useful
cooling
energy
8LLP 10 3L 2 9
Saturated liquid at p2=p3=p4 1
Saturated liquid at p1=p5=p6=p3_LLP

21. More detailed absorption cooling
Refrigeration and air conditioning (Ramesh et al)