LiBr水溶液を用いた垂直管流下液膜式の吸収器と再生器の性能  [in Japanese] The Performance of Vertical Falling Film Absorber and Generator Using LiBr Aqueous Solution  [in Japanese]

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作動媒体にLiBr水溶液を用いる, 熱を駆動源とする吸収冷凍機, 吸収ピートポンプにおける吸収器, 再生器の作動特性について研究した.装置形状は高さ1m, 外径15.7mmの垂直管外流下液膜式で, 管内に冷却 (加熱) 水を流した.液膜流れは層流から乱流に亘り, 3つの冷却 (加熱) 水流量で実験した.層流域では, 流量の低下に従って流下液の濃度が変化して吸収 (再生) の温度推進力が小さくなり, 吸収 (蒸発) 速度|<I>n</I><SUB>A</SUB>|が減少した.一方, 乱流域では流下液の濃度変化は小さく, 流量が増加すると液膜の熱伝達係数<I>h</I><SUB>L</SUB>, 物質移動係数<I>k</I><SUB>L</SUB>が増加することにより, |<I>n</I><SUB>A</SUB>|は増加した.以前に行った高さ0.58mの結果との比較から, 塔の高さが長くなると低流量域で|<I>n</I><SUB>A</SUB>|が減少するが, 高流量域では高さによる違いはみられなかった.また, 冷却 (加熱) 水流量が小さくなると|<I>n</I><SUB>A</SUB>|は減少した.これらの実験結果は, 流下液膜の<I>h</I><SUB>L</SUB>, <I>k</I><SUB>L</SUB>を用いて気液界面の温度, 濃度を求める計算法による値とよく一致した.

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 |<I>n</I><SUB>A</SUB>| 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, |<I>n</I><SUB>A</SUB>| 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 <I>h</I><SUB>L</SUB> and mass transfer coefficient <I>k</I><SUB>L</SUB>, for the falling film. In the small flow rate region, the values of |<I>n</I><SUB>A</SUB>| for this column (height : 1 m) are less than those for a 0.58 m column, which we reported previously. Both the values of|<I>n</I><SUB>A</SUB>| for 1 m and 0.58 m columns, however, are the same in the large flow rate region. |<I>n</I><SUB>A</SUB>| decreases asthe flow rate of the cooling (heating) water decreases.<BR>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 <I>h</I><SUB>L</SUB> and <I>k</I><SUB>L</SUB> of the falling film.


  • Chemical engineering  

    Chemical engineering 24(6), 828-833, 1998-11-20 

    The Society of Chemical Engineers, Japan

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