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首页> 外文期刊>Journal of Heat Transfer >Boiling Heat Transfer Rates for Small Precisely Placed Water Droplets on a Heated Horizontal Plate
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Boiling Heat Transfer Rates for Small Precisely Placed Water Droplets on a Heated Horizontal Plate

机译：精确放置在加热的水平板上的小水滴的沸腾传热速率

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Two small horizontal surfaces, heated to temperatures up to 220℃, were cooled by small (50-300 mm diameter) room-temperature droplets at 1 atmosphere pressure. One surface was a 10 × 10 mm thin-film nichrome heater that was used to measure heat fluxes below 100 W/cm2. The other surface, used for fluxes in excess of 100 W/cm~2, was a solid copper heater with an 8X8 mm exposed surface. A continuous jet droplet generator coupled with two mutually perpendicular deflection plates was used to manipulate the path of constant diameter water droplets so that the impact of the drops could be precisely located on the heated surfaces. The droplet generator and the deflection plates were employed so that the effect of the impact frequency, droplet diameter, droplet velocity and spacing on the resulting heat transfer rates could be studied under controlled conditions. Optimal droplet spacing between 0.75 and 1.5 times the droplet diameter increased the critical heat flux approximately 30 percent above the value that was achieved when the drops were deposited in one location. For area-averaged mass flow rates less than about 0.08 g/(cm~2s), there was no trend in the critical heat flux with the Weber number. However, for larger mass flux rates, the critical heat flux increased with an increasing Weber number. The measured critical heat flux values were roughly twice the heat flux of traditional pool boiling for identical superheat temperatures. Two droplet cooling dimensionless critical heat flux correlations are proposed as a function of Weber and Strouhal numbers; one for a single stream of drops and the other for drops that are spaced across the heated surface. The correlation for the spaced droplets is a function of a dimensionless droplet spacing on the heater.
机译：在1个大气压下，用小的（直径为50-300毫米）室温液滴冷却加热到220℃的两个小水平表面。一个表面是一个10×10 mm的薄膜镍铬合金加热器，用于测量低于100 W / cm2的热通量。用于通量超过100 W / cm〜2的另一个表面是带有8X8 mm暴露表面的固态铜加热器。连续的喷射液滴发生器与两个相互垂直的偏转板相连，用于操纵直径恒定的液滴的路径，从而使液滴的冲击可以精确地定位在加热的表面上。使用液滴产生器和偏转板，以便可以在受控条件下研究冲击频率，液滴直径，液滴速度和间距对所得传热速率的影响。在0.75到1.5倍液滴直径之间的最佳液滴间距可使临界热通量比液滴沉积在一个位置时所获得的值高大约30％。对于小于约0.08 g /（cm〜2s）的面积平均质量流率，临界热通量没有随韦伯数变化的趋势。但是，对于较大的质量通量率，临界热通量随韦伯数的增加而增加。对于相同的过热温度，测得的临界热通量值大约是传统池沸腾热通量的两倍。提出了两个液滴冷却的无量纲临界热通量相关性，作为韦伯和斯特劳哈尔数的函数。一个用于单个液滴流，另一个用于在加热表面上隔开的液滴。隔开的液滴的相关性是加热器上无量纲的液滴间距的函数。

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