Vapor AbsorptionRefrigeration Systems Based On Ammonia-Water Pair

• 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.

Vapor AbsorptionRefrigeration Systems Based On Ammonia-Water Pair

For Ammonia-Water pair

Circulation ratio- Is the ratio of the mass of the weak solution to the refrigerant mass flowrate.

=mλ ws/m

Condenserm1= m2= m

Q c=m(h1-h2)

Expansion Valvem2=m3=m

h2=h3

Evaporatorm3=m4=m

QE=m(h4-h3)

Absorberm + mss = mws

QA=mh4+λh10-(1+λ)mh5

Pumpm5=m6=mws

Wp=mws(h6-h5)

Wp=λm(h6-h5)

Heat Exchangerm6=m7=mws

m8=m9=mss

Generatorm7=m8+m1

QG=mh1+λmh8-(1+λ)mh7

Expansion Valvem9=m10=mws

h9=h10

COP=QE/(QG+Wp)

Comparison Between Compression and Absorption Refrigeration Systems