共查询到18条相似文献,搜索用时 78 毫秒
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将纵向涡强化换热技术应用于矩形管槽,研究以水为换热介质在过渡流状态下的换热效果。实验结果表明有纵向涡发生器的换热效果明显优于无纵向涡发生器的情况。利用PHEON ICS计算软件对实验进行数值模拟,模拟值与实验值符合较好。在此基础上,改变纵向涡的翼高和形状来模拟,发现两者均为换热影响的因素,相比之下,高宽比为0.4纵向涡发生器的换热效果比高宽比为0.5和0.6的要好。而采用相同高宽的矩形翼时,N u高于三角翼,但其换热性能指标却低于直角三角翼。 相似文献
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采用雷诺应力湍流模型对半封闭射流冲击移动平板进行了数值分析,得到了不同平板速度下的流场和温度场结构以及近壁面湍流强度和平板表面局部努谢尔数分布曲线。结果表明,平板速度的提高会导致流场和温度场关于射流中心线呈现非对称性,且在流场一侧形成二次漩涡区。平板表面的湍流强度值随平板速度的提高而提高,而冲击区域的局部努谢尔数峰值则随平板速度的提高而降低。当平板速度大于入口射速时,表面平均努谢尔数值随平板速度的提高而逐渐升高。当平板速度提高到入口射流速度两倍时,冲击点处的平板表面湍流强度值升高了约40%,努谢尔数峰值下降了约60%,而平板表面的平均努谢尔数值则提高了30%以上。 相似文献
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阵列射流冲击冷却流场与温度场的数值模拟 总被引:3,自引:0,他引:3
采用数值模拟方法对冲击冷却的流动和传热过程进行了三维数值研究。特别研究了在冲击孔叉排方式下,相邻孔间距、冲击距离以及射流入口雷诺数对冲击表面冷却流动传热特性的影响规律。 相似文献
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采用数值模拟方法对冲击水浴式洗涤净化过程中顶部浸没气体射流冲击液体的气液流动过程进行了研究。着重揭示了在气体射流冲击液体初始阶段的冲击行为过程,获得了最大冲击深度等表征冲击流动的参数及其变化规律。数值模拟得到了与实验相同的结论。数值研究发现:冲击凹坑的发展变化经历了凹坑形成、凹坑长大、凹坑膨胀停滞和凹坑上浮运动4个阶段;气体射流动量的大小是影响最大冲击深度的重要因素之一;在气体射流动量一定的情况下,最大冲击深度随着喷口尺寸的增加而减小;管口浸没深度对气体射流最大冲击深度的影响不大。 相似文献
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阵列射流冲击冷却换热特性的数值研究 总被引:1,自引:0,他引:1
运用数值计算的方法对不同流动取向的多排孔冲击射流冷却特性进行了三维模拟,并对有初始横向流的多排孔冲击射流冷却特性进行了数值研究,揭示出射流雷诺数、流动方向、初始横向流对冲击冷却传热特性的影响规律。结果表明:研究范围内,射流雷诺数越大,冲击靶面换热效果越好;冲击腔室两端都设为出口时努赛尔数峰值所对应的射流驻点区向下游偏移最小且换热效果最好;当横流雷诺数与射流雷诺数之比大于0.5之后,有横流时的冲击射流冷却局部努赛尔数比无横流时有较为显著下降。 相似文献
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Zeyi JIANG Cuicui LIU Xinxin ZHANG Qiang MA Yusheng SUN .School of Mechanical Engineering University of Science Technology Beijing Beijing China .China Aviation Planning Construction Development Co LTD China 《热科学学报(英文版)》2011,(5)
Flow and heat transfer characteristics of slot jets impingement to a cylindrical convex surface are numerically investigated.Suitable turbulence models have been determined through comparison with the experimental data.Flow structures are described and impingement heat transfer characteristics are discussed.The effects of Re,H/B and D/B on single-slot jets impingement heat transfer are analyzed and heat transfer characteristics of multiple-slot jets are investigated.The results show that:Gas flows along the... 相似文献
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不同喷口结构对冲击式速冻机换热特性影响的模拟研究 总被引:1,自引:0,他引:1
为研究不同喷口结构时速冻机内流动和换热特性、优化速冻机的气流组织和提高换热效率,以冲击式速冻机为研究对象,设计了5种不同形式的条缝喷口,分别对这5种喷口喷射气流流动和换热特性进行数值模拟,对比分析喷射区域的气流组织,研究了被冲击的板带表面的温度场分布和Nu变化。研究表明:孔板式喷口的流量较小,为167. 9 m~3/h,换热的均匀性较差;组合式渐缩喷口的气流组织最佳,喷口出口的流量最大,为226. 2 m~3/h,同时板带表面的平均Nu也最高,达到29. 6。 相似文献
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This paper is about a separated reattaching flow over a hot rectangular obstacle. Two types of incoming flow are examined in order to show the influence of the external zone of the flow on the reattachment process. It comes about due to a wall jet and a boundary layer. The inner region of these two flows is similar, but their external regions are extremely different. The separating and reattaching flow phenomena are of particular interest in engineering fields such as for an aeronautical application. Wall jet flow over an obstacle occurs in many engineering applications such as environmental discharges, heat exchangers, fluid injection systems, cooling of combustion chamber wall in a gas turbine, automobile design, and others. In electronics cooling, the prediction of the Nusselt number distribution along the obstacles is necessary before the design of the apparatus. For a heated obstacle at a constant temperature, T = 350 K and an aspect ratio of 10 (L = 10 H), the problem parameters are: (a) jet exit Reynolds number (Re) ranged from 1000 to 50000, (b) incoming flow configuration (boundary layer and wall jet). The ratio between the thickness of the nozzle (b) to the obstacle height (H) are examined simultaneously. The formulation is based on the SST k–ω turbulence model. The results show that the increasing of nozzle thickness; enhances the heat transfer and considerably modifies the stagnation point location. The highest incoming flow momentum provides the greatest values of average Nusselt number. Such as the boundary layer case in comparison with the wall jet cases. The average Nusselt number is correlated according to problem parameters . 相似文献
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倾斜射流对移动平板表面紊动和传热特性的影响 总被引:1,自引:0,他引:1
采用雷诺应力湍流模型和Simplic算法对半封闭槽道内倾斜射流冲击移动平板的流动和传热特性进行了数值模拟,研究了不同射流角度和不同平板移动速度下平板近壁湍动能和板面努塞尔数的变化.结果表明:射流角度和平板运动速度对平板近壁湍动能和表面努塞尔数值分布影响显著;当入射角与平板运动方向相同时,板速的升高提高了近壁面的湍动能,但是降低了冲击区域的局部努塞尔数值;平板表面的平均努塞尔数值随板速的提高先降低后大幅升高,高速下角度对平板表面的平均传热效果影响较小;当入射角为80°,平板运动方向与入射方向相反且板速和射流速度相同时,在移动平板表面能够获得较佳的紊动和传热效果. 相似文献
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Vishal A. Patil Vinod Narayanan 《Nanoscale and Microscale Thermophysical Engineering》2013,17(2):183-197
An experimental study of a submerged 125-μm circular microscale jet impingement is presented. These jets flows are associated with low exit Reynolds number and a correspondingly high, subsonic Mach number. Detailed distributions of heated and adiabatic wall temperature, and local and average Nusselt number variations are presented for five laminar exit Reynolds numbers in the range of 690 to 1770 at three nozzle-to-surface spacings of 2, 4, and 6 times the nozzle diameter. The corresponding jet exit Mach numbers range between 0.26 and 0.63. An infrared radiometer is used in conjunction with a heated-thin-foil technique to measure detailed surface temperatures. Results indicate that the adiabatic surface temperature distribution is relatively insensitive to nozzle-to-surface spacing within the parameter range studied. With an increase in Reynolds number, the adiabatic surface temperature decreases significantly near the stagnation point. The average Nusselt numbers are higher compared to Martin's correlation [1] for large Reynolds numbers. A similar observation has been reported previously in a numerical study on microscale jet impingement [5] and attributed to compressibility of the flow and the possible existence of a slip flow. 相似文献
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针对涡轮叶片尾缘吸力面热应力集中,容易造成叶片尾部烧毁的现象,提出端部冲击扰流柱结构,采用Realizable k-ε湍流模型和增强壁面函数分析涡轮叶片尾缘内部流场和吸力面换热特性,研究不同冲击孔与扰流柱排列方式的影响,揭示端部冲击扰流柱结构的流场与换热机理。研究表明,端部冲击扰流柱结构对于改善吸力面的换热效果要优于中间冲击扰流柱结构,对端壁的换热有显著提高;各表面平均换热系数均随着压比的增大而增大,顺排结构时,冲击孔换热最强,扰流柱换热次之;叉排结构时,冲击孔换热最强,隔板迎风换热次之;近距离冲击,顺排的综合效果优于其它几种结构,而远距离冲击,叉排的综合效果最好,其吸力面温度分布较均匀。 相似文献