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Modeling of Marangoni Convection Induced at Lithium Bromide Aqueous Solution's Surface and its Application to Improve Absorbers Performance

溴化锂水溶液表面诱导的马兰戈尼对流模拟及其在提高吸收器性能中的应用

基本信息

批准号：
13650234
负责人：
NISHIMURA Nobuya
金额：
$ 2.24万
依托单位：
Osaka City University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

项目摘要

The absorption refrigerators are drawing great attention as a CFCs-free refrigerator friendly to the global environment. And authors have been revealed the refrigerating performance increases to double with addition of surfactant into the LiBr aqueous solution. But detailed mechanisms of the surfactant's absorption enhancement effect have not been clarified yet.Therefore, in the study, effects of an addition of surfactant to a lithium bromide aqueous sohticn have been investigated experimentally for both thin stagnant pool and falling liquid film of LiBr aqueous solution. N-octanol and 2 ethyl-hexanol were used as surfactants.The Marangoni convection occurred at/beneath the solution surface in the very beginning of steam absciption was observed both by a real-time type laser holographic visualization and by temperature measurements with extremely fine gauge thermocouples. Generation and growth of the Marangoni convection were both observed and evaluated quantitatively by the flow visua … More lization. Furthermore, solution's surface temperatures with and withoutaddition of the surfactant were measured minutely. Cell's formation pattern and migration speed at the surface were measured varying the initial surfactant's concentration ranging from 0 to 50000ppm and the shallow liquid layer thickness ranging from 2 to 5mm. And spacio-temporal scales of the Marangoni convection were determined. Also solution temperature changes at the surface were compared. Temperature increases when the surfactant was added to its solubility limit became almost double than that case of no surfactant. From these temperature differences, effects of the surfactant on absorber's performances were estimated by a calculation quantitatively with diffusion coefficient as an evaluation value.Furthermore, effects of the surfactant (n-octanol) on performances of the vertical flat plate absorber have been investigated. Refrigerating capacity increases with increase of the surfactant concentration. In case of the surfactant concenlration is 100ppm, the refrigerating capacity become larger about 3 to 4 times than that case of no surfactant. Less

吸收式制冷机作为一种对全球环境友好的无CFC制冷机正引起人们的极大关注。在LiBr水溶液中加入表面活性剂，可使其制冷性能提高一倍。但表面活性剂的吸收增强效应的详细机理尚未阐明，因此，在本研究中，实验研究了表面活性剂添加到LiBr水溶液中对LiBr水溶液的薄停滞池和下降液膜的影响。以正辛醇和2-乙基己醇为表面活性剂，采用激光全息实时显示和极细热电偶测温技术，观测到了水蒸气脱落初期溶液表面及下方的Marangoni对流。用流动观察仪对Marangoni对流的产生和发展进行了定量观察和评价， ...更多信息化。此外，还对添加和不添加表面活性剂时溶液的表面温度进行了细致的测量.在表面活性剂初始浓度为0 ~ 50000 ppm，浅液层厚度为2 ~ 5 mm的条件下，测定了细胞在表面的形成模式和迁移速度。确定了Marangoni对流的时空尺度。还比较了表面处的溶液温度变化。当表面活性剂加入到其溶解度极限时，温度增加几乎是没有表面活性剂的情况下的两倍。根据这些温差，以扩散系数为评价值，定量计算了表面活性剂对吸收器性能的影响，并研究了表面活性剂（正辛醇）对垂直平板吸收器性能的影响。制冷量随表面活性剂浓度的增加而增加。当表面活性剂浓度为100 ppm时，制冷量比无表面活性剂时大3 ~ 4倍。少