水平伝熱面における核沸騰について(第1報)

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The method of temperature measurement, utilizing the refraction of light passing through fluid very close to a heated surface, was employed by Schmidt and Saunders (1935-1937). We extended this method and studied the nucleate boiling on horizontal heating surface. When the heating surface sets up normal temperature gradient, the path of light, which has incident angle parallel to the surface, is determined by next equation : (dy/dx)^2=2N(θ_b-θ) θ : Temperature at height y above the surface. θ_b : Temperature at height b above the surface. n : Refractive index. N=-(1/n) (dn/dθ) Let Φ denote the maximum inclination of the path of light to the surface after passing through the boundary layer. Φ is measured experimentally. Then, Δθ is obtained using the following relations : Φ^2=2NΔθ N=4°36×10^<-4>1/℃ (for D-line at 100℃) The values of Δθ measured by optical method showed good agreement with those by thermocouples. Moreover, we devised a simple was of measuring the average Φ varying with time. The effect of the temperature distribution before the edge of the heating surface upon the angle Φ was negligibly small. The light after passing through the layer has the dark and light stripes due to temperature disturbance, and they represent the motion of fluid. The images of bubbles and flow of fluid were ptographed at the same time using revolving drum. At lower heat flux these stripes move uniformly, showing the laminar motion of the temperature disturbances, and at higher heat flux the flow of motion becomes turbulent. The thickness of temperature boundary layer could be also measured easily. The curve of thickness of boundary layer plotted vs, coefficient of heat transfer has a bending point, which shows the difference between laminar heat transfer and turbulent heat transfer. This agrees with the results of measuring of motion in the boundary layer.
一般社団法人日本機械学会の論文
1952-02-11

水平伝熱面における核沸騰について(第1報)

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