Two step evaporator-absorber
The evaporator and the absorber are split into two sections. This design allows the cycle
concentration to be lower than a conventional absorber/evaporator. The lower concentrations
mean the unit is more reliable, operates with increased efficiency, and has a lower corrosion
potential.
Chilled water flows through both evaporator sections. It enters the lower evaporator tubes first. It
then moves to and through the upper evaporator tubes before it leaves the chiller.
Each evaporator operates at a slightly different temperature and pressure. The refrigerant in the
lower evaporator boils at a slightly higher temperature than in the upper one. The chilled water is
cooled in two steps.
The absorber is split into two sections also. A strong solution enters the top of the upper absorber.
It flows down through the upper absorber bundle.
The upper bundle operates at a lower vapor pressure. As a result, the upper evaporator can
operate at a lower pressure and temperature.
The solution flows into the top of the lower absorber section. When the LiBr solution enters the
lower absorber section it is already diluted by the refrigerant vapor that boiled off in the upper
evaporator. Bacause the lower evaporator is the first step of the chilled water cooling, the dilute
solution vapor pressure is adequate to maintain the lower evaporator at the required temperature
and pressure.
The cooling tower water enters the lower absorber section first, keeping the vapor pressure of the
weaker solution as low as possible.
YHAU-C Single Effect Steam-Fired Absorption Chiller16
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