THE PERFORMANCE OF VERTICAL FALLING FILM ABSORBER AND GENERATOR USINGLIBR AQUEOUS-SOLUTION

This paper describes the performance characteristics of the absorber a nd the generator in an absorption refrigerator and heat pump, which ca n be driven by heat sources, using LiBr solution as working fluid. The absorber (generator) is composed of a vertical outer falling film col umn (height: 1 m and outer diameter: 15.7 mm), into which cooling (hea ting) water streams. Experiments are made at the LiBr solution flow ra tes from laminar to turbulent regime, and at three flow rates of cooli ng (heating) water. In the laminar flow region, the absorption (evapor ation) rate \n(A)\ drops as the LiBr solution flow rate decreases, bec ause the concentration of the falling solution changes greatly and the temperature driving force for absorption (generation) diminishes. On the other hand, \n(A)\ increases as the flow rate increases in the tur bulent flow region, because the change of the falling solution concent ration is small and the increasing flow rate enlarges the Values of he at transfer coefficient h(L) and mass transfer coefficient k(L) for th e falling film. In the small flow rate region, the Values of \n(A)\ fo r this column (height: 1 m) are less than those for a 0.58 m column, w hich we reported previously. Both the values of \n(A)\ for Im and 0.58 m columns, however, are the same in the large flow rate region. \n(A) \ decreases as the flow rate of the cooling (heating) water decreases. These experimental results agree well with the values obtained by the calculation method in which the temperature and the concentration at the vapor-liquid interface can be computed by using h(L) and k(L) of t he falling film.