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
