1. Refrigeration & Air-Conditioning
UNIT II
Vapour Absorption Refrigeration System

2. Simple VAR System

3. Practical VAR System Improvements / Modifications: Analyzer
Rectifier or Dehydrator
Two Heat Exchangers

4. COP of an Ideal VAR System
In an Ideal VAR System,
Heat QG is given to refrigerant in generator,
Heat QC is discharged to atmosphere or cooling water from condenser and absorber,
Heat QE is absorbed by refrigerant in evaporator,
Heat QP is added to refrigerant due to pump work
Neglecting Heat due to pump work QP, we have, according to first law of thermodynamics,
QG + QE = QC (1)

5. COP of an Ideal VAR System
Let, TG = Temp. at which heat QG is given to generator TC = Temp. at which heat QC is discharged to atmosphere or cooling water from condenser and absorber TE = Temp. at which heat QE is absorbed in the evaporator Since, VAR system can be considered as a perfectly reversible system, therefore the initial entropy of system must be equal to entropy of system after the change in its condition. 𝑄 𝐺 𝑇 𝐺 + 𝑄 𝐸 𝑇 𝐸 = 𝑄 𝐶 𝑇 𝐶 𝑄 𝐺 𝑇 𝐺 + 𝑄 𝐸 𝑇 𝐸 = 𝑄 𝐸 + 𝑄 𝐺 𝑇 𝐶 from equation (1)

6. COP of an Ideal VAR System
𝑄 𝐺 𝑇 𝐺 + 𝑄 𝐸 𝑇 𝐸 = 𝑄 𝐸 𝑇 𝐶 + 𝑄 𝐺 𝑇 𝐶 𝑄 𝐺 𝑇 𝐺 - 𝑄 𝐺 𝑇 𝐶 = 𝑄 𝐸 𝑇 𝐶 − 𝑄 𝐸 𝑇 𝐸 On solving and simplifying, we get
𝐶𝑂𝑃 𝑚𝑎𝑥 = 𝑇 𝐸 𝑇 𝐶 − 𝑇 𝐸 𝑇 𝐺 − 𝑇 𝐶 𝑇 𝐺

7. Electrolux Refrigerator (Ammonia Hydrogen Refrigerator / Three Fluids Absorption System)
These systems offer several advantages over conventional systems such as: i. High reliability due to absence of moving parts ii. Very little maintenance iii. Systems require only low grade thermal energy, hence no need for any grid power iv. Silent operation

8. Electrolux Refrigerator (Ammonia Hydrogen Refrigerator / Three Fluids Absorption System)