The document describes the components and operating principles of a vapor absorption refrigeration system (ARS). It includes diagrams of the vapor compression and vapor absorption cycles showing the main components like the generator, absorber, evaporator, condenser and solution pump. It also provides equations for the thermodynamic analysis of each component based on mass, energy and species balances.

1. Compressor
Condenser
Expansion Valve
Evaporator
3
2
1
4
5 6
7 8
Heat Exchaner
Condenser
Evaporator
Generator
Absorber
14
3
5
6
1
4
Pump
Expansion valve
2
21
20
15
16
Valve
17
24
25
18
19
22 23
Vapor Compression Refrigeration System Vapor Absorption Refrigeration System
Vapor Absorption Refrigeration System
(ARS) or Vapor Absorption Cycle
Huge
electricity
is required
Low quality/
waste heat may
be utilized
Ozone depletion by CFCs Environment friendly

2. Vapor Absorption
Refrigeration System
Heat recovery
Reduction in utilities
Hot utilities/ cold utilities
No harmful working fluid
Refrigerant – Absorbent Pairs
Absorption of NH3 into H2O
Absorption of H2O into LiBr
Freezing point of refrigerant is also important
Low grade heat is used
Oil, flue gas, steam, hot water, solar etc.
Overall energy used is large (COP is low)
Vapor Absorption Refrigeration System (ARS)
Heat Exchaner
Condenser
Evaporator
Generator
Absorber
14
3
5
6
1
4
Pump
Expansion valve
2
21
20
15
16
Valve
17
24
25
18
19
22 23

3. Assumptions
•Steady State
•Refrigerant (water) at condenser outlet is saturated liquid
•Refrigerant (water) at evaporator outlet is saturated vapor
•LiBr solution at the absorber outlet is a strong solution and it is at the
absorber temperature
•The outlet temperature from the absorber and from generators correspond
to equilibrium conditions of the mixing and separation, respectively.
•Negligible pressure losses in pipelines.equipments
•Heat loss is negligible, other than which is intentionanly transferred (at HPG,
Evp, Cond. & abs.)
•Generator is driven by pressurized hot water
•Chilled water is produced
•Heat rejection to cooling water in condenser and absorber

4. Thermodynamic Analysis
Overall Mass Balance:
𝒎𝒊𝒏 − 𝒎𝒐𝒖𝒕 = 𝟎
𝒎𝒊𝒏 . 𝒙𝒊𝒏 − 𝒎𝒐𝒖𝒕 . 𝒙𝒐𝒖𝒕 = 𝟎
Species Mass Balance:
Where m is the mass flow rate
x is the mass fraction of LiBr in the solution
Calculation of x required the knowledge of
T & P data at specified location of the
flowsheet
Energy Balance (First Law of Thermodynamics):
𝒎𝒊𝒏 . 𝒉𝒊𝒏 − 𝒎𝒐𝒖𝒕 . 𝒉𝒐𝒖𝒕 + 𝑸𝒊𝒏 − 𝑸𝒐𝒖𝒕 + 𝑾 = 𝟎

5. Generator
Thermodynamic Analysis
Heat Exchaner
Condenser
Evaporator
Generator
Absorber
14
3
5
6
1
4
Pump
Expansion valve
2
21
20
15
16
Valve
17
24
25
18
19
22 23
𝒎𝟔 = 𝒎𝟏𝟓 + 𝒎𝟏𝟒
𝒙𝟔𝒎𝟔 = 𝒙𝟏𝟓𝒎𝟏𝟓 + 𝒙𝟏𝟒𝒎𝟏𝟒
𝑸𝒈 = 𝒎𝟏𝟒𝒉𝟏𝟒 + 𝒎𝟏𝟓𝒉𝟏𝟓-𝒎𝟔𝒉𝟔
𝒎𝟏𝟖 = 𝒎𝟏𝟗

6. Solution pump
Thermodynamic Analysis
Heat Exchaner
Condenser
Evaporator
Generator
Absorber
14
3
5
6
1
4
Pump
Expansion valve
2
21
20
15
16
Valve
17
24
25
18
19
22 23
𝒎𝟒 = 𝒎𝟏𝟓
𝒙𝟒𝒎𝟒 = 𝒙𝟏𝟓𝒎𝟏𝟓
𝒘𝒑 = 𝒎𝟒
𝑷𝟓 − 𝑷𝟒
𝜼𝒑𝝆𝟒

7. Solution Heat Exchanger
Thermodynamic Analysis
Heat Exchaner
Condenser
Evaporator
Generator
Absorber
14
3
5
6
1
4
Pump
Expansion valve
2
21
20
15
16
Valve
17
24
25
18
19
22 23
𝒎𝟔 = 𝒎𝟓
𝒎𝟏𝟓𝒉𝟏𝟓 + 𝒎𝟓𝒉𝟓 = 𝒎𝟏𝟔𝒉𝟏𝟔 + 𝒎𝟔𝒉𝟔 = 𝒒𝑯𝑬
𝒙𝟔 = 𝒙𝟓
𝒎𝟏𝟔 = 𝒎𝟏𝟓 𝒙𝟏𝟔 = 𝒙𝟏𝟓
𝜼 =
𝒉𝟏𝟓 − 𝒉𝟏𝟔
𝒉𝟏𝟓 − 𝒉𝟏𝟔
∗
𝒉𝟏𝟔
∗
𝒆𝒗𝒂𝒍𝒖𝒂𝒕𝒊𝒐𝒏 𝒐𝒇 𝒉𝟏𝟔 𝒂𝒕 𝑻𝟓,
𝒘𝒉𝒊𝒄𝒉 𝒊𝒔 𝒂𝒃𝒔𝒐𝒓𝒃𝒆𝒓 𝒕𝒆𝒎𝒑𝒆𝒓𝒂𝒕𝒖𝒓𝒆

8. Absorber
Thermodynamic Analysis
Heat Exchaner
Condenser
Evaporator
Generator
Absorber
14
3
5
6
1
4
Pump
Expansion valve
2
21
20
15
16
Valve
17
24
25
18
19
22 23
𝒎𝟏𝟕 + 𝒎𝟑 = 𝒎𝟒
𝒙𝟏𝟕𝒎𝟏𝟕 + 𝒙𝟑𝒎𝟑 = 𝒙𝟒𝒎𝟒
𝑸𝒂𝒃𝒔 = 𝒎𝟏𝟕𝒉𝟏𝟕 + 𝒎𝟑𝒉𝟑 − 𝒎𝟒𝒉𝟒
𝒎𝟐𝟒 = 𝒎𝟐𝟓

9. Evaporator
Thermodynamic Analysis
Heat Exchaner
Condenser
Evaporator
Generator
Absorber
14
3
5
6
1
4
Pump
Expansion valve
2
21
20
15
16
Valve
17
24
25
18
19
22 23
𝒎𝟐 = 𝒎𝟑
𝑸𝒆𝒗𝒑 = +𝒎𝟑𝒉𝟑 − 𝒎𝟐𝒉𝟐
𝒎𝟐𝟐 = 𝒎𝟐𝟑

10. Condenser
Thermodynamic Analysis
Heat Exchaner
Condenser
Evaporator
Generator
Absorber
14
3
5
6
1
4
Pump
Expansion valve
2
21
20
15
16
Valve
17
24
25
18
19
22 23
𝒎𝟏 = 𝒎𝟏𝟒
𝑸𝒄𝒐𝒏𝒅 = 𝒎𝟏𝟒𝒉𝟏𝟒 − 𝒎𝟏𝒉𝟏
𝒎𝟐𝟎 = 𝒎𝟐𝟏

11. Expansion Valve
Thermodynamic Analysis
Heat Exchaner
Condenser
Evaporator
Generator
Absorber
14
3
5
6
1
4
Pump
Expansion valve
2
21
20
15
16
Valve
17
24
25
18
19
22 23
𝒎𝟏 = 𝒎𝟐
𝒉𝟏 = 𝒉𝟐

12. Solution Scheme
Thermodynamic Analysis
Heat Exchaner
Condenser
Evaporator
Generator
Absorber
14
3
5
6
1
4
Pump
Expansion valve
2
21
20
15
16
Valve
17
24
25
18
19
22 23
Assume the following variables are specified
(can be justified from DoF analysis):
𝑻𝒈𝒆𝒏 = 𝟗𝟎 ℃, 𝑻𝒂𝒃𝒔 = 𝟑𝟓 ℃
𝑻𝒄𝒐𝒏𝒅 = 𝟑𝟓 ℃, 𝑻𝒆𝒗𝒑 = 𝟒 ℃
Calculation of cond. & evp. conditions
Both cond. and evp. contain pure species:
1. Water in case of LiBr-H2O
2. Ammonia in case of H2O-NH3)
𝒉𝟏 = 𝒇(𝑻𝒄𝒐𝒏𝒅)
𝒉𝟑 = 𝒇(𝑻𝒆𝒗𝒑)
𝑷𝒈𝒆𝒏 = 𝑷𝒄𝒐𝒏𝒅
𝑷𝒂𝒃𝒔 = 𝑷𝒆𝒗𝒑
𝑷𝒄𝒐𝒏𝒅 = 𝒇(𝑻𝒄𝒐𝒏𝒅)
𝑷𝒆𝒗𝒑 = 𝒇(𝑻𝒆𝒗𝒑)
𝒉𝟏𝟒 = 𝒇(𝑻𝒈𝒆𝒏, 𝑷𝒈𝒆𝒏)

13. Solution Scheme (Contd.)
Thermodynamic Analysis
Heat Exchaner
Condenser
Evaporator
Generator
Absorber
14
3
5
6
1
4
Pump
Expansion valve
2
21
20
15
16
Valve
17
24
25
18
19
22 23
𝑻𝒈𝒆𝒏 = 𝟗𝟎 ℃, 𝑻𝒂𝒃𝒔 = 𝟑𝟓 ℃
𝑻𝒄𝒐𝒏𝒅 = 𝟑𝟓 ℃, 𝑻𝒆𝒗𝒑 = 𝟒 ℃
For absorber
𝒙𝟒 = 𝒇(𝑻𝒂𝒃𝒔, 𝑷𝒂𝒃𝒔) 𝒉𝟒 = 𝒇(𝑻𝒂𝒃𝒔, 𝒙𝟒)
For generator
𝒙𝟏𝟓 = 𝒇(𝑻𝒈𝒆𝒏, 𝑷𝒈𝒆𝒏) 𝒉𝟏𝟓 = 𝒇(𝑻𝒈𝒆𝒏, 𝒙𝟏𝟓)
For pump
𝒉𝟓 = 𝒘𝒑 + 𝒉𝟒

14. Solution Scheme (Contd.)
Thermodynamic Analysis
Heat Exchaner
Condenser
Evaporator
Generator
Absorber
14
3
5
6
1
4
Pump
Expansion valve
2
21
20
15
16
Valve
17
24
25
18
19
22 23
For utilities
𝒉𝟏𝟖 = 𝒇(𝑻𝟏𝟖) 𝒉𝟏𝟗 = 𝒇(𝑻𝟏𝟗)
𝒉𝟐𝟎 = 𝒇(𝑻𝟐𝟎) 𝒉𝟐𝟏 = 𝒇(𝑻𝟐𝟏)
𝒉𝟐𝟐 = 𝒇(𝑻𝟐𝟐) 𝒉𝟐𝟑 = 𝒇(𝑻𝟐𝟑)
𝒉𝟐𝟒 = 𝒇(𝑻𝟐𝟒) 𝒉𝟐𝟓 = 𝒇(𝑻𝟐𝟓)
For expansion valve
𝒉𝟐 = 𝒉𝟏
𝒉𝟐𝒇 = 𝒇(𝑻𝒆𝒗𝒑) 𝒉𝟐𝒇𝒈 = 𝒇(𝑻𝒆𝒗𝒑)
𝒙𝟐
𝒒
=
𝒉𝟐 − 𝒉𝟐𝒇
𝒉𝟐𝒇𝒈 𝒉𝟐 = 𝒉𝟐𝒇 + (𝟏 − 𝒙𝟐
𝒒
)𝒉𝟐𝒇𝒈

15. Solution Scheme (Contd.)
Thermodynamic Analysis
Heat Exchaner
Condenser
Evaporator
Generator
Absorber
14
3
5
6
1
4
Pump
Expansion valve
2
21
20
15
16
Valve
17
24
25
18
19
22 23
Calculation of mass flow rate
𝑸𝒆𝒗𝒑 = 𝒎𝟐(𝟏 − 𝒙𝟐
𝒒
)𝒉𝟐𝒇𝒈
𝒎𝟐 =
𝑸𝒆𝒗𝒑
(𝟏 − 𝒙𝟐
𝒒
)𝒉𝟐𝒇𝒈
𝒎𝟐 = 𝒎𝟑
Mass balance across absorber
𝒎𝟒 = 𝒎𝟑 + 𝒎𝟏𝟕
𝒙𝟒𝒎𝟒 = 𝒙𝟑𝒎𝟑 + 𝒙𝟏𝟕𝒎𝟏𝟕

16. Solution Scheme (Contd.)
Thermodynamic Analysis
Heat Exchaner
Condenser
Evaporator
Generator
Absorber
14
3
5
6
1
4
Pump
Expansion valve
2
21
20
15
16
Valve
17
24
25
18
19
22 23
Solution Heat Exchanger
𝜼 =
𝒉𝟏𝟓 − 𝒉𝟏𝟔
𝒉𝟏𝟓 − 𝒉𝟏𝟔
∗
𝒉𝟏𝟔 = 𝒉𝟏𝟓 − 𝜼(𝒉𝟏𝟓 − 𝒉𝟏𝟔
∗
)
𝒉𝟏𝟔
∗
= 𝒇(𝑻𝒂𝒃, 𝒙𝟏𝟓)
𝑻𝟏𝟔 = 𝒇(𝒉𝟏𝟔, 𝒙𝟏𝟓)
𝒒𝑯𝑬 = 𝒎𝟏𝟕(𝒉𝟏𝟓 − 𝒉𝟏𝟔)
𝒉𝟓 = 𝒉𝟒 + 𝒘𝒑
𝒒𝑯𝑬 = 𝒎𝟒(𝒉𝟔 − 𝒉𝟓)
𝒉𝟔 = 𝒉𝟓 +
𝒒𝑯𝑬
𝒎𝟒
𝑻𝟔 = 𝒇(𝒉𝟔, 𝒙𝟒)
𝒉𝟏𝟕 = 𝒉𝟏𝟔

17. Solution Scheme (Contd.)
Thermodynamic Analysis
Heat Exchaner
Condenser
Evaporator
Generator
Absorber
14
3
5
6
1
4
Pump
Expansion valve
2
21
20
15
16
Valve
17
24
25
18
19
22 23
Calculation of mass flow rate
𝒎𝟏𝟖 =
𝑸𝒈𝒆𝒏
𝒉𝟏𝟖 − 𝒉𝟏𝟗
𝒎𝟐𝟎 =
𝑸𝒄𝒐𝒏𝒅
𝒉𝟐𝟏 − 𝒉𝟐𝟎
𝒎𝟐𝟐 =
𝑸𝒆𝒗𝒑
𝒉𝟐𝟑 − 𝒉𝟐𝟐
𝒎𝟐𝟒 =
𝑸𝒂𝒃𝒔
𝒉𝟐𝟓 − 𝒉𝟐𝟒
𝑪𝑶𝑷 =
𝑸𝒆𝒗𝒑
𝑸𝒈𝒆𝒏 + 𝒘𝒑

19. Heat Exchaner
Condenser
Evaporator
Generator
Absorber
14
3
5
6
1
4
Pump
Expansion valve
2
21
20
15
16
Valve
17
24
25
18
19
22 23
2
3
4
1
5
8
6
17
18
11 12
13 14
15
16
9
7
9