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根据纵向涡强化传热技术提出了新型的强化换热管——锥形内肋管,运用数值模拟方法,研究了新型强化换热管结构参数锥底宽度a、导程P、肋深e和Re数对Nu、沿程阻力系数f及传热综合因子η的影响。结果表明:换热管内壁面边缘处产生了较多的微小涡流,有效破坏了流动边界层,强化了传热。在充分湍流的条件下,流体Re越小、e越小,其综合传热性能越强。当Re<15 000时,a对η的影响要大于P;在过渡点后, P对η影响较大。通过综合传热性能分析,给出了适合不同Re区间的锥形内肋优化参数。 相似文献
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利用FLUENT软件对省煤器横截面积恒定的4种矩形鳍片管的传热和流动特性进行了三维数值模拟,将数值模拟结果与试验结果进行了比较.并用场协同理论进行了分析.结果表明:Re数在2 000~5 000范围内,5 mm×20 mm矩形鳍片管的换热区域速度场和温度场协同度较高并且流动阻力系数较小,其综合强化传热效果好. 相似文献
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在湍流状态下对对排排列的凸胞换热管的传热及流动特性进行了数值模拟,讨论了凸胞排数对换热性能的影响,分析了强化换热机理;以换热性能Nu、阻力系数f及综合换热性能PEC指数为目标函数,利用多目标遗传算法对凸胞换热管的深度H、半径R及节距P进行优化。结果表明:凸胞附近的湍流强度明显高于光滑管,且2排凸胞数的换热管综合换热性能更优;在所研究的范围内,结合响应面分析发现,结构参数对目标函数的敏感性表现为H﹥R﹥P;维持Re=13136,优化结构与初始结构相比,换热性能至少提高75%,阻力系数减少14.5%。 相似文献
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通过实验的方法研究了一种花瓣形扁通道内翅换热管的对流换热和阻力特性,拟合了所测Re范围内对流换热和阻力实验关联式,并运用相同质量流量、相同泵功率和相同阻力降这3种准则比较了采用不同材质时翅片管与普通光管之间的传热效果。结果表明,翅片材质对换热强化效果有较大影响,无论采用哪种材质,花瓣形扁通道内翅管均有较强的换热效果,特别是在低盅条件下,强化效果更加明显。 相似文献
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提出一种新型的正反两个方向交替扭转的扭带模型,并基于ANSYS FLUENT软件在层流状态下(Re=400~18 00)对换热管中插入新型扭带的换热特性、流体阻力特性和综合性能指标进行数值模拟研究。对y=3.0,4.5,6.0三种扭率下的无缺口正反扭转扭带与传统单一方向扭带进行对比研究,并对扭率y=3.0的无缺口正反扭转扭带和带有三角、半圆及方形缺口的正反扭转扭带进行了对比计算。研究结果表明:插入不同扭率的扭带,换热管的努赛尔数Nu、摩擦系数f与综合性能PEC值均随着扭率的减小而增大;相同扭率下无缺口的正反扭转扭带在强化换热效果和综合性能表现上要优于传统扭带;扭率为3.0时,无缺口的正反扭转扭带比带三种缺口的正反扭转扭带换热效果好,而缺口的存在可以大幅度地降低插入扭带产生的摩擦阻力,且缺口的面积越大,摩擦和换热效果降低越多。 相似文献
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通过模拟和实验的方法研究在湍流工况下(3 000Re10 000)换热器管内插入不同扭带模型后的传热特性和阻力特性。区别于传统螺旋扭带,提出一种顺时针与逆时针交替扭转的正反扭带。对不同扭率的传统扭带以及扭率为3的无缺口和半圆缺口正反转扭带进行模拟计算,并将模拟结果与实验结果进行对比验证。结果表明:在湍流流态下,雷诺数越小,扭带的强化换热效果表现越好;对不同扭率的扭带,其努塞尔数、摩擦系数和综合性能指标随扭率的减小而增大;扭率为3时,两种正反扭带的强化换热效果均优于传统扭带,无缺口正反扭带的换热效果最好;模拟计算的结果数据与实验结果数据比较,最大误差不超过8%。 相似文献
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It is novel and better method that microencapsulated phase change material (MPCM) slurry and the tube with twisted tape inserts are adopted together to enhance convective heat transfer. In this paper, numerical analyses were carried out to study laminar heat transfer and friction characteristics of MPCM slurry in a circular tube with twisted tape inserts. It is found that the MPCM slurry in the tube with twisted tape insert leads to the best performance of convective heat transfer for the bigger apparent specific heat and the intensive swirl flow. Furthermore, the modified average Nusselt number increases with decreasing bulk Stefan number, twisted ratio and increasing Re, while the friction factor increases with increasing Re and decreasing twisted ratio. It is also found that the heat transfer enhanced efficiency increases with increasing Re and decreasing Steb, and the heat transfer enhancement effects of twisted tape for low Steb slurry are better than that for high Steb slurry. Moreover, the thermal-hydraulic performance ratios increase to a peak, then decrease gradually with increasing Re for different twist ratio. The performance ratio increases with decreasing the twist ratio only in a definite Re range, and the Re range decreases with decreasing twist ratio. 相似文献
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光管内插入扭带传热与流动阻力的试验研究 总被引:3,自引:1,他引:2
为了研究管内强化换热技术,对三根不同结构参数的扭带插入光管的换热特性和流体动力学特性进行了试验研究。试验以空气为工质,Re在8000~10^5之间,管外被水冷却。对大量实验数据用多元线性回归法得到了具有较高精度的扭带管的传热系数和摩擦系数的统计关联式,分析了扭带管的传热与流阻性能,为换热器的设计及改造提供了理论依据。 相似文献
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Paisarn Naphon Tanapon Suchana 《International Communications in Heat and Mass Transfer》2011,38(2):236-241
In the present study, the heat transfer characteristics and the pressure drop of the horizontal concentric tube with twisted wires brush inserts are investigated. The inner diameters of the inner and outer tubes are 15.78 and 25.40 mm, respectively. The twisted wire brushes are fabricated by winding a 0.2 mm diameter of the copper wires over a 2 mm diameter of two twisted iron core-rod with three different twisted wires densities of 100, 200, 300 wires per centimeter. The plain tube with full-length twisted wires brush and regularly spaced twisted wires brush with 30 cm spacer length inserts are tested. Cold and hot water are used as working fluids in shell side and tube-side, respectively. The test runs are performed at the hot water Reynolds number ranging between 6000 and 20000. The inlet cold and hot water temperatures are 15, 20 °C, and between 40 and 50 °C, respectively. Effect of twisted wires density, inlet fluid temperature, and relevant parameters on heat transfer characteristics and pressure drop are considered. Twisted wire brushes insert have a large effect on the enhancement of heat transfer, however, the pressure drops also increase. 相似文献
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用基液代替水来配置微胶囊相变悬浮液,并对实验数据的准确性进行了检验。在等热流密度环境下对管道内的该悬浮液进行加热实验,对相变微胶囊悬浮液的质量分数、St、入口过冷度、粒径和Re等因素影响强化换热的效果进行了分析。结果显示影响微胶囊相变悬浮液管内层流换热最主要的因素是微胶囊的质量分数和St。 相似文献
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The effect of peripherally-cut twisted tape with alternate axis (PT-A) on the fluid flow and heat transfer enhancement characteristic in a uniform heat flux circular tube has been experimentally investigated. Experiments were conducted using water as a testing fluid in a turbulent tube where the Reynolds number was varied from 5000 to 20,000. Peripherally-cut twisted tape (PT) and typical twisted tape (TT) were also tested in similar conditions, for comparison. Evidently, the heat transfer rates in the tube fitted with the PT-A, PT and TT are respectively enhanced up to 184%, 102% and 57% of that in the plain tube. In the present Reynolds number range tested, the PT-A, PT and TT offer the maximum thermal performances at constant pumping power of 1.25, 1.11 and 1.02, respectively. In addition, the correlations of the Nusselt number, friction factor and thermal performance were developed for the tube equipped with the PT-A in terms of peripherally-cut tape width ratio (w/W), Reynolds number (Re) and Prandtl number (Pr). 相似文献
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M.M.K. Bhuiya M.S.U. Chowdhury M. Islam J.U. Ahamed M.J.H. Khan M.R.I. Sarker M. Saha 《International Communications in Heat and Mass Transfer》2012
In the present study, the heat transfer performance and friction factor characteristics in a circular tube fitted with twisted wire brush inserts were investigated experimentally. The twisted wire brush inserts were fabricated with four different twisted wire densities of 100, 150, 200, and 250 wires per centimeter by winding a 1 mm diameter of the copper wire over a 5 mm diameter of two twisted iron core-rods. Heat transfer and friction factor data in tubes were examined for Reynolds number ranging from 7,200 to 50,200. The results indicated that the presence of twisted wire brush inserts led to a large effect on the enhancement of heat transfer with corresponding increase in friction factor over the plain tube. The Nusselt number and friction factor of using the twisted wire brush inserts were found to be increased up to 2.15 and 2.0 times, respectively, than those over the plain tube values. Furthermore, the heat transfer performance was evaluated to assess the real benefits of using those type of inserts and the performance was achieved 1.85 times higher compared to the plain tube based on the constant blower power. Finally, correlations were developed based on the data generated from this work to predict the heat transfer, friction factor, and thermal performance factor for turbulent flow through a circular tube fitted with the twisted wire brush inserts in terms of wire density (y), Reynolds number (Re), and Prandtl number (Pr). 相似文献
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Heat transfer in a solar water heater could be enhanced by means of twisted tapes, inserted inside the fluid flow tubes, which induce swirl flow and act as turbulence promoters. Experimental investigations for a solar water heater with twisted tape inserts having twist pitch to tube diameter ratio ranging from 3–12 have been carried out for varying mass flow rates. The results on heat transfer and friction data have been found to compare well with available results. Within the range of investigated parameters, the heat transfer in the twisted tape insert collectors has been found to increase by 18–70%, whereas the pressure drop increased by 87–132%, as compared to plane collectors. An expression correlating the Nusselt numbers in twisted tape and plane collectors, the twist pitch ratio has been developed in the form of Nus/Nu=1.3+2.88/y, which predicts the heat transfer within the range of the present investigation. Results conclude that such collectors would be preferable for higher grade energy collection as it is also at higher rate.Solar water heaters having twisted tape inserts inside the flow tubes perform better than the plane ones. It has been observed that heat losses are reduced (due to the lower value of the plate temperature) consequently increasing the thermal performance by about 30% over the plane solar water heaters under the same operating conditions. The effect of twisted-tape geometry, flow Reynolds number and intensity of solar radiation on the thermal performance of the solar water heater has been presented. It has been found that the twisted-tape collectors perform remarkably better in the lower range of flow Reynolds number (Re≈12,000), beyond which the increase in thermal performance is monotonous. It has also been found that such collectors might perform even better at higher values of intensity of solar radiation. 相似文献