Experimental study on the adiabatic absorption of water vapor into LiBr–H2O solutions

This paper reports an experimental study on the adiabatic absorption of water vapor into aqueous LiBr solutions. Three different arrangements for the fluid flow are considered: mono-disperse droplets, unstable jets breaking into poli-disperse droplets and films falling along ramps. In all cases the flow was due to gravity, without any artificially generated pressure difference. No additives were added to the solution to enhance the transport processes. It is shown how solution saturates faster when distributed in jets or in a falling film than in droplets, yielding mean mass transfer coefficients above 15 × 10−5 m/s. Falling films can handle higher flows per unit of dispenser area and, simultaneously, offer more contact area with water vapor per unit length, letting the solution reach 85% approach to equilibrium within the first 20 cm of fall. This allows us to conclude that the required absorption chamber volume per unit cooling power is significantly smaller with this arrangement than with droplet or even jet flows. Calculated values indicate that 2–3 l/kW should be enough.