Vapor absorption refrigeration systems based on the ammonia-water pair are one of the oldest refrigeration systems. In these systems, ammonia acts as the refrigerant and water acts as the absorbent. These systems operate at higher pressures than atmospheric pressure. Safety precautions must be taken because ammonia is toxic and flammable. The circulation ratio is defined as the ratio of the mass of the weak solution to the mass flow rate of the refrigerant.

1. Vapor Absorption
Refrigeration Systems
Based On Ammonia-Water Pair

2. • Vapour absorption refrigeration system based on ammonia-
water is one of the oldest refrigeration systems.
• Ammonia is used as a refrigerant and water is used as an
absorbent.
• Lithium bromide systems operate under very low pressures,
the ammonia-water system is operated at pressures much
higher than atmospheric .
• Ammonia is both toxic and flammable. Hence, these systems
need safety precautions.

3. Vapor Absorption
Refrigeration Systems
Based On Ammonia-Water Pair

4. For Ammonia-Water
pair
Circulation ratio
- Is the ratio of the
mass of the weak
solution to the
refrigerant mass
flowrate.
λ=mws/m

5. Condenser
m1= m2= m
Qc=m(h1-h2)
Expansion Valve
m2=m3=m
h2=h3
Evaporator
m3=m4=m
QE=m(h4-h3)

6. Absorber
m + mss = mws
QA=mh4+λh10-(1+λ)mh5
Pump
m5=m6=mws
Wp=mws(h6-h5)
Wp=λm(h6-h5)
Heat Exchanger
m6=m7=mws
m8=m9=mss

7. Generator
m7=m8+m1
QG=mh1+λmh8-(1+λ)mh7
Expansion Valve
m9=m10=mws
h9=h10
COP=QE/(QG+Wp)

8. Comparison Between Compression and Absorption
Refrigeration Systems