Temperature measurements near the heating surface at high heat fluxes in pool boiling of 2-propanol/water mixtures
Temperature measurements near the heating surface at high heat fluxes in pool boiling of 2-propanol/water mixtures
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DOI：
10.1016/j.ijheatmasstransfer.2015.10.042
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发表时间：
2016-02
影响因子：
5.2
通讯作者：
H. Sakashita
中科院分区：
文献类型：
--
作者：
H. Sakashita
为了研究二元混合物增强CHF的机制，本文使用微型热电偶在高热通量下测量了靠近加热表面的局部温度，用于3 mol%的2-丙醇/水混合物在向上朝向的12 mm直径的圆形表面上的池沸腾。在加热表面上方的各个位置处测量的温度轨迹的变化表明，2-丙醇浓度的分布在垂直和径向方向上具有很强的非均匀性：2-丙醇浓度在加热表面的中心部分的加热表面附近较高，在加热表面的外围较低。基于温度波动的低峰值对应于混合物的局部饱和温度的假设，确定2-丙醇的局部浓度。这一假设使得在垂直和径向方向上的浓度分布的定量表示。的混合物的表面张力的变化进行了评估的基础上推导出的局部值的饱和温度和混合物的组成。有人发现，在加热表面附近的表面张力急剧增加的加热表面的方向，这表明强烈的Marangoni对流诱导在加热表面附近的液体/蒸汽界面。
To examine the mechanism of CHF enhancement with binary mixtures, this paper measured local temperatures close to a heating surface using a micro-thermocouple at high heat fluxes for pool boiling of a 3 mol% of 2-propanol/water mixture on an upward-facing 12 mm diameter circular surface. The variations in temperature traces measured at various locations above the heating surface indicate that the distributions of 2-propanol concentration have strong non-uniformities in the vertical and radial directions: 2-propanol concentration is higher in the vicinity of the heating surface at the central part of the heating surface and lower in the periphery of the heating surface. The local concentration of 2-propanol was determined based on the assumption that low peak values of temperature fluctuations correspond to the local saturation temperatures of the mixture. This assumption enabled a quantitative representation of the concentration distributions in the vertical and radial directions. The variations in the surface tension of the mixture were evaluated based on the deduced local values of the saturation temperature and the composition of the mixture. It was found that near the heating surface the surface tension increases steeply in the direction of the heating surface, suggesting that intensive Marangoni convection is induced at the liquid/vapor interface near the heating surface.