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以R600a压力式封闭系统喷雾冷却过程为研究对象,对其换热过程进行分析。对液滴撞击热面后的状态进行建模,分析了其运动状态。通过忽略液膜的对流换热,引入韦伯数来简化并修正雾滴与热源表面的对流换热系数关联式;借鉴二次成核理论,通过单位时间内,单位面积上覆盖的雾滴数量对核态沸腾换热系数关联式修正。通过上述分析,以对流换热和核态沸腾换热两种机理为中心,建立了新的换热系数关联式。通过与其他文献的关联式、实验测量值进行比较、不同工质进行比较、不同实验系统比较,发现该式预测值和实验测量值偏差在±20%以内,能够很好地预测压力式封闭系统喷雾冷却过程的换热系数。 相似文献
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雾化喷射冷却的机理及模型研究 总被引:2,自引:0,他引:2
雾化喷射冷却的换热机理十分复杂,目前其研究还很不成熟。本文从喷射雾滴的特性参数出发,以被冷却表面上形成的喷射液膜为对象,考虑了冷却液体向环境的散热,建立质量、能量守恒方程,得到半经验半解析的雾化喷射换热模型。其中,本文提出真换热系数和显换热系数的概念,认为显换热系数受空间散热影响,而真换热系数只与喷雾动量有关。最后设计了雾化喷射局部换热实验,对模型进行检验,结果表明,该模型能够较好地符合实验所得的换热系数及加热面表面温度沿喷射半径的分布趋势。 相似文献
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This work involved continual- and intermittent-spray cooling heat transfer experiments on a flat surface to study the effects of the spray cycle, duty ratio, and spray time. The spray droplet parameters were similar, while the heat transfer coefficients for continual-spray cooling were appreciably larger than those of intermittent-spray cooling for the same pressure; however, the heat dissipated per kilogram of water for the intermittent-spray cooling was larger, especially in the non-boiling region. The results show that an optimal spray cycle and optimal duty ratio make more efficient use of the coolant in intermittent-spray cooling. 相似文献
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A spray cooling heat transfer experiment on straight fin surface under acceleration conditions was conducted to investigate the effects of acceleration, flow rate, and nozzle height. The results show that the acceleration can improve the heat transfer performance in a limited way. In addition, whether in the acceleration or stationary condition, the flow rate as well as the nozzle height has the same impact on the spray cooling performance. It is also observed that the surface temperature can influence the effect of flow rate on spray cooling performance, and the cooling performance becomes worse with the increase of nozzle height. 相似文献
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Experiments on triangular and rectangular array jet impingement and single-phase spray cooling have been performed to determine the effect of both cooling techniques on heat transfer coefficient (h) and the coolant mass flux required for a given cooling load. Experiments were performed with circular orifices and nozzles for different H/D values from 1.5 to 26 and Reynolds number range of 219 to 837, which is quite lower than the ranges employed in widely used correlations. The coolant used was polyalphaolefin. The experiments simulated the boundary condition produced at the surface of the stator of a high power low-density generator or motor. For the custom fabricated orifices, commercial nozzles, and conditions used in this study, both cooling configurations showed enhancement of heat transfer coefficient as H/D increases to a certain limit after which it starts to decrease. The heat transfer coefficient always increases with Reynolds number. In keeping with previous studies, single-phase spray cooling technique can provide the same heat transfer coefficient as jets at a slightly lower mass flux, but with much higher-pressure head. Special Nud correlations that account for the range of parameters and coolant studied in this work are derived. 相似文献
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Systematic experiments were conducted for the spray cooling of high-temperature stainless steel using three different types of industrial sprays: full cone and flat hydraulic nozzles and a flat air-mist nozzle. In the present study, a wide range of mass flux (1.5–30 kg/m2sec) is covered, which has never been thoroughly investigated before. Orientations with respect to gravity and spray angle were also explored. The data have been analyzed and correlated. The results of this study will be important to the product quality control in industries by providing a good estimation of heat flux at different mass flux, spray types, and surface temperatures, especially for spray cooling of stainless steel and other metals with similar thermal properties. 相似文献
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Air-atomized spray cooling of a hot moving AISI 304 steel plate of 6 mm thickness has been investigated experimentally by varying water flow rate and plate velocity at a fixed nozzle-to-plate distance. It is found that the heat transfer coefficient is a non-linear function of surface temperature. The result shows that the cooling rate increases with an increase in the water flow rate. The highest cooling rate has been found for the static plate, whereas for a moving plate, an increasing cooling rate trend has been observed with increasing plate velocity. 相似文献