1998 Volume 24 Issue 6 Pages 828-833
This paper describes the performance characteristics of the absorber and the generator in an absorption refrigerator and heat pump, which can be driven by heat sources, using LiBr solution as working fluid. The absorber (generator) is composed of a vertical outer falling film column (height : 1 m and outer diameter : 15.7 mm), into which cooling (heating) water streams. Experiments are made at the LiBr solution flow rates from laminar to turbulent regime, and at three flow rates of cooling (heating) water. In the laminar flow region, the absorption (evaporation) rate |nA| drops as the LiBr solution flow rate decreases, because the concentration of the falling solution changes greatly and the temperature driving force for absorption (generation) diminishes. On the other hand, |nA| increases as the flow rate increases in the turbulent flow region, because the change of the falling solution concentration is small and the increasing flow rate enlarges the values of heat transfer coefficient hL and mass transfer coefficient kL, for the falling film. In the small flow rate region, the values of |nA| for this column (height : 1 m) are less than those for a 0.58 m column, which we reported previously. Both the values of|nA| for 1 m and 0.58 m columns, however, are the same in the large flow rate region. |nA| decreases asthe 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 hL and kL of the falling film.
