1. Lecture Objectives:
Introduce HW3
Learn about sorption chillers

2. Sequence of operation (PRC research facility)
Set Point (SP)
Mixture 2
Mixture 3
Mixture 1
DBTSP
DPTSP
Control logic:
Mixture in zone 1: IF (( TM<TSP) & (DPTM<DPTSP) ) heating and humidifying
Heater control: IF (TSP>TSA) increase heating or IF (TSP<TSA) decrease heating
Humidifier: IF (DPTSP>DPTSA) increase humidifying or IF (DPTSP<DPTSA) decrease humid.
Mixture in zone 2: IF ((TM>TSP) & (DPTM<DPTSP) ) cooling and humidifying
Cool. coil cont.: IF (TSP<TSA) increase cooling or IF (TSP>TSA) decrease cooling
Humidifier: IF (DPTSP>DPTSA) increase humidifying or IF (DPTSP<DPTSA) decrease hum.
Mixture in zone 3: IF ((DPTM>DPTSP) ) cooling/dehumidifying and reheatin
Cool. coil cont.: IF (DPTSP>DPTSA) increase cooling or IF (DPTSP<DPTSA) decrease cooling

3. HW3
Writhe a sequence of operation instruction list for the air handling unit from HW2 (problems: 3&4)

4. HW3 You will need to define:
what environmental variable/condition change
- Temperature and RH of ambient air, Q cooling, Q heating, …..
which variables can you control
recirculation rate, recirculation position, Total flow rate, TCC,…
C) which variable will you control
- …..
D) how are you going to “move” between different
operation schemes
E) writhe “if - else” set of instruction for different controlled devices while considering different operation scheme (see the example I gave you in class)

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

6. Absorption cooling cycle
Relatively simple thermodynamics with addition of mixtures (water – ammonia)
Rich solution of
Heat
H2O
H2O + NH3
Rich solution of
H2O
H2O + NH3

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

8. Impact of Pressure

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

14. Mixing of two streams with heat rejection (Absorber)
=pure
NH3 (x2=1) m3
mixture of
H2O and NH3 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)
What happens if
X2 ≠ 1 ?
Substitute into (3)
From adiabatic mixing
(from previous slide)

15. Change of pressure (pump)
Sub cooled
liquid at p2 2
Saturated
liquid
at p1 1 p1
≠p2 m1
=m2 p2
Saturated liquid at x1
=x2 2 p1
Saturated liquid at 1
x1=x2

16. Heat transfer with separation into liquid and vapor (Generator)
Saturated
vapor
Heat
=2V
Sub cooled
liquid
Saturated
liquid
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 :
What happens if 1 is not sub
cooled liquid ?
Apply mass and energy
balance In the heat exchanger
defines
point 2
in graph
Defines points 3 and 4 in graph

17. Heat rejection with transformation from vapor to liquid (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

18. Throttling process (Expansion valve)
Saturated vapor 1 2V 2 h1
=h2 T1 1 2 p1
Saturated liquid at p1
≠p2 T2 2L
Saturated
liquid m1
=m2 p2
At the end of expansion
we get from X1=X2 liquid
X2V vapor and
X2L liquid
Saturated liquid at x1
=x2 p1
≠p2 x1
=x2 h1
=h2

19. Simple absorption system3V 3L
3LLP

20. 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

21. 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

22. 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