Abstract: Adding a little bit 2-ethylhexanol additives to lithium bromide-water solution can enhance the absorption dramatically in LiBr-water chiller.As a result,COP of the chiller is improved.But the heat transfer is going bad in falling film evaporator where 2-ethylhexanol water solution is working.To find the reasons,this paper focuses on the contact angle by comparing the 2-ethylhexanol water solution and deionized water on the different metal plates.Experimental results show that adding a little bit 2-ethylhexanol additives to the water makes the contact angle bigger than no additives.Wettability is changed to be lower.Hence,the heat transfer in the falling film evaporator is decreased.It also shows that 40 mg稬^-1 2-ethylhexanol water solution on the zinc coated steel has the smallest contact angle,next is stainless steel and the copper has the biggest contact angle.Concentration of the 2-ethylhexanol water solution has no obvious effect on the contact angle.

Key words: 2-ethylhexanol, falling film evaporator, contact angle, surfactant, absorption refrigeration

摘要： 向溴化锂水溶液中添加微量异辛醇表面活性剂,能显著增强溴化锂吸收式制冷机的吸收作用,提高制冷能力。但添加了异辛醇后,吸收式制冷机中的降膜蒸发器的换热效果却不能保证得到强化,有时出现降膜蒸发器的换热效果变差的现象。为探究导致换热变差的原因,本研究通过测量异辛醇水溶液和金属板表面的接触角,发现水中加入微量异辛醇后接触角普遍增大,湿润性变差,使降膜蒸发器的传热变差。通过测量并比较同浓度异辛醇水溶液在不同金属表面的接触角,得出40 mg·L^-1时异辛醇水溶液在镀锌钢板表面的湿润性最好,其次是不锈钢板,在紫铜表面的湿润性最差。异辛醇水溶液的浓度变化对每种金属板接触角没有明显影响。

关键词: 异辛醇, 降膜蒸发器, 接触角, 表面活性剂, 吸收式制冷