1. Lecture Objectives:
Analysis of Absorption Cooling Cycles

2. Carnot Cycles
COPvapor_compression=Qcooling/Pelectric COPmax=Tcooling/(Tenviromnet-Tcooling)
COPabsorption=Qcooling/Qheating COPmax= Tcooling/(Tenviromnet-Tcooling) ∙ (Theat_source-T environment)/ Theat_source
COPmax_absorption= COP vapor compression x Correction for VC cycle

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

4. 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’
2’ , 2’’
Saturated liquid at p1’ 1
Saturated liquid at p1
Cooling
tower
Pumping
energy
COP= Q cooling / Q heating (Pump ???)

5. 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!

6. Use of precooling (system improvement #2)

7. 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

8. System improvement #3 Generator with of Enrichment NH3 8V 9 8L 10 8LLP
Different 8V 9 8L 10
8LLP 11

9. 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

10. Ammonia Enrichment Process (rectification)

11. 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

12. Example of H2O-NH3 System
Text Book (Thermal Environmental Engineering) Example 5.5
HW 1:
Solve the problem 5.6 from the textbook (LiBr-H2O)
Beside example 5.6, you will need to study example 5.6 and 5.7
Due date February 25th.

13. LiBr-H2O Systems

14. LiBr-H2O Systems

15. Twine vessel LiBr-H2O Systems

16. Useful information about LiBr absorption chiller
Practical Tips for Implementation of absorption chillers
Identify and resolve any pre-existing problems with a cooling system, heat rejection system, water treatment etc, before installing an absorption chiller, or it may be unfairly blamed.
Select an absorption chiller for full load operation (by the incorporation of thermal stores if necessary) as COP will drop by up to 33% at part-load.
Consider VSD control of absorbent pump to improve the COP at low load.
Consider access and floor-loading (typical 2 MW Double-effect steam chiller 12.5 tons empty, 16.7 tones operating).
Ensure ambient of temperature of at least 5°C in chiller room to prevent crystallization.

17. System with no pump (Platen-Munter system)
H2O-NH3 + hydrogen