Civil Engineering Reference
In-Depth Information
Fig. 12.4
Example of a
cascade vapor-compression
refrigeration cycle
They differ from the vapor-compression cycles in two important respects:
• Downstream of the evaporator (point 1), the refrigerant in the vapor state is
absorbed by a secondary substance, called an absorbent, to form a liquid
solution. This solution is then pumped to a higher pressure (condenser pressure)
by means of a pump which requires much less work than vapor compression
does, because of the low specific volume of the solution. The mechanical input
power is consequently very low.
Note that the formation of the liquid solution is an exothermic reaction.
Since the amount of refrigerant that can be dissolved into the absorbent
liquid increases as the solution temperature decreases, a cooling system may
