Absorption of water vapour in the falling film of water–lithium bromide inside a vertical tube at air-cooling thermal conditions

Abstract In the absorbers of air-cooled water–lithium bromide absorption chillers, the absorption process usually takes place inside vertical tubes with external fins. In this paper we have carried out an experimental study of the absorption of water vapour over a wavy laminar falling film of water–lithium bromide on the inner wall of a smooth vertical tube. The control variables for the experimental study were; absorber pressure, solution mass flow rate, solution concentration and cooling water temperature. Relatively high cooling water temperatures were selected to simulate air-cooling thermal conditions. The parameters considered to assess the performance of the absorber were; the mass absorption flux, the outlet solution degree of subcooling and the falling film heat transfer coefficient. The results indicate that in water cooling thermal conditions the mass absorption fluxes are in the range 0.001–0.0015 kg·m−2·s−1, whereas in air-cooling thermal conditions the range of mass absorption values decreases to 0.00030–0.00075 kg·m−2·s−1.