共查询到20条相似文献,搜索用时 180 毫秒
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本文报道了微重力条件下90°弯管内气液两相流型实验结果。弯管内径12.7 mm,弯曲半径76.5mm,气、 液两相表观流速分别为1.0—23.6 m/s和0.09—0.5 m/s。本文分析了观测到的弹状流、弹-环过渡流和环状流的典型特 征,比较了与微重力直管内相应流型间及常重力弯管两相流型间的异同。 相似文献
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表面活性剂对倾斜上升气液两相流流型的影响 总被引:2,自引:0,他引:2
应用电导断层测量技术研究表面活性剂添加对倾斜上升气液两相流流型的影响,实验工质为空气/水、空气/100 mg/kg十二烷基硫酸钠(SDS)水溶液。结果表明,当倾角较小时(2.5°和5°),添加少量纯度为95%的SDS到空气/水两相流系统,可以推迟了分层流型向环状流型的转换,使其发生在较高的气体流速条件下;与水平流动的实验结果类似,在本文的实验条件下没有观测到表面活性剂对塞状流型、弹状流型转换特性的影响。随着倾角的增大(10°),表面活性剂添加对气液两相流流型的影响更为显著,在空气/水气液两相流系统中没有观测到分层流动,而加入表面活性剂后在一定范围内存在分层流动。 相似文献
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微通道内超临界二氧化碳的压降与传热特性 总被引:4,自引:0,他引:4
进行了微通道内超临界CO2的局部和平均传热与压降特性实验研究。结果表明,临界点附近物性参数的剧烈变 化使压降增大,但传热被大大强化。同时也发现,系统压力、质量流速及CO2温度对流动与传热特性有重要影响。在大 量实验数据的基础上,得出了冷却条件下水平微通道内超临界CO2强制对流换热关联式。 相似文献
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分别以0.2%、0.5%、1%质量分数的Al2O3-H2O纳米流体和去离子水为实验工质,在高2mm,宽1mm的矩形微细通道内进行纳米流体与非纳米流体两相沸腾传热和压降对比研究。实验结果表明:增加质量通量对两种工质换热系数影响都较小,但增加热流密度可提高换热系数;在相同工况下,与水基液相比,采用Al2O3-H2O纳米流体换热系数明显增大,且随着纳米流体质量分数的增加而增加,对于该实验换热系数可提高8%~17%;随着纳米颗粒质量分数和质量通量的增加,两相摩擦压降显著增大。 相似文献
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Gülay Yakar 《实验传热》2019,32(1):25-35
In the present study, convective heat transfer to the air from a heating tube attached to conical baffles with rift was experimentally examined. The air entering the test section first contacts the large surface of the conical baffle. Therefore, the conical baffle both directs the air toward the heating surface and increases the heat transfer surface area. In the experiments, baffles with inclination angles of 45°, 60°, and 80° were used. The baffles were placed on the heating tube at the pitch of 15 mm. The temperature of the heating fluid (water) was kept fixed at 65°C. In addition to the riftless baffles, the experiments were carried out by using baffles with a rift spacing of 1.5 and 3.5 mm so that the boundary layer separation mechanism could be accelerated. Experimental results for eight different velocities of airflow (2–20 m/s) were presented. For the inclination angle of 60°, the increase in the heat transfer of the baffle with rift was 13% at a rift spacing of 1.5 mm and 4% at a rift spacing of 3.5 mm according to the riftless baffle. In addition, for the inclination angle of 60°, the pressure drop values of the riftless and the rift spacing of 1.5 and 3.5 mm were almost the same. 相似文献
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Rafael Cortell Bataller 《Physics letters. A》2008,372(14):2431-2439
This Letter presents a numerical study of the flow and heat transfer of an incompressible FENE-P fluid over a non-isothermal surface. The governing partial differential equations are converted into ordinary differential equations by a similarity transformation. The effects of the thermal radiation are considered in the energy equation, and the variations of dimensionless surface temperature and dimensionless surface temperature gradient, as well as the heat transfer characteristics with various physical parameters are graphed and tabulated. Two cases are studied, namely, (i) the sheet with prescribed surface temperature (PST case) and (ii) the sheet with prescribed heat flux (PHF case). Moreover, the mechanical characteristics of the corresponding flow are also presented. 相似文献
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In this paper the effects of electrohydrodynamics (EHD) on heat transfer enhancement and flow pattern of R134a two-phase mixture, flowing in a horizontal tube, were numerically investigated. A uniform DC electric field was applied through a circular stainless steel rod along the centerline of tube, while the tube was considered as a grounded electrode. The simulations, in order to investigate the EHD mechanism, were performed for a constant heat flux 2000 W/m2, voltages between 0 and 5 kV, inlet volume fractions 65% and 85%, mass fluxes from 30 kg/m2s to 50 kg/m2s and electrode diameters between 1.57 mm and 2.4 mm. These flow conditions correspond to stratified flow. The flow regime redistributions under the applied electric field was obtained. The results show that the steady state condition was occurred at the time about 900 ms. According to the results, enhancement ratio is directly proportional to voltage, and it is reversely proportional to electrode diameter, mass flux and inlet volume fraction. 相似文献
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波纹板式空冷器阻力与传热特性实验研究 总被引:5,自引:0,他引:5
在可改变风量和热水流量的实验条件下,对波纹板式空冷器的阻力与传热特性进行实验研究。得到了空气侧的阻力降关联式以及两侧的对流换热系数关联式,其适用于热水雷诺数在2000-8000之间、空气雷诺数在2000-10000之间。在相同工况下,比较了波纹板式、光管式和翅片管式空冷器的性能指标,结果表明:迎面风速在2.45-4.1 m/s之间,波纹板式空冷器传热系数达到100-160 W/m2/℃;约比光管式提高70%,但只有以管束外表面为基准的翅片管式传热系数的六分之一;板式空冷器单位体积换热量约是翅片管式空冷器的1.5倍,是光管式的15倍;板式空冷器单位功耗换热量约是光管式空冷器的5.5倍,而翅片管式空冷器与光管式空冷器则相差不大。 相似文献
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In this study, heat transfer coefficients and pressure drops of R-134a inside round and flat tubes are investigated experimentally with mass flux of 450, 550, and 650 kg m?2 s?1 at saturation temperatures of 35°, 40°, and 45°C. The effects of mass flux and saturation temperature on heat transfer coefficient and pressure drop are examined. The maximum enhancement factor and pressure drop penalty are obtained by flat tube (FT-2) up to 2.101 at 450 kg m?2 s?1 and 3.01 at 650 kg m?2 s?1, respectively. The correlation for flat tubes is proposed to predict the heat transfer coefficient within ±20% error. 相似文献