共查询到19条相似文献,搜索用时 203 毫秒
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非共混沸合物泠凝器的传热强化 总被引:1,自引:0,他引:1
通过对螺旋隔板和花瓣管在冷凝过程中的强化传热性能分析,从理论上阐明了由螺旋隔板与花瓣管配搭形成的冷凝器可有效地强化非共沸混合物蒸汽的冷凝传热。 相似文献
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基于强化传热技术,以光滑椭圆管为基本研究对象,对比不同扁平度n及导程S的扁平螺旋管,通过合理的简化与假设,采用计算流体力学(CFD)的方法对扁平螺旋管进行数值模拟研究,以期为该换热设备结构优化设计及实际工程应用提供参考。研究证明:扁平螺旋管与光管对比,扁平螺旋管内产生了明显的旋流运动,促进了流体在垂直于轴向方向的混合,使得管内流体的轴向速度增大,且这种混合使得换热管边界层厚度变薄,保持了较高的温度梯度,达到了强化传热的目的;扁平螺旋换热管的旋转程度越大(即相同的截面尺寸,S越小),换热管的强化换热的性能越好,但换热管内流体介质的流动阻力也相应越大,所以导程S在84~150之间为扁平螺旋管导程的优选区间;扁平螺旋管的压扁程度不一定越扁越好,当换热管的扁平度过大时,会导致扁平螺旋管的努塞尔数Nu急剧下降,压降△P急剧增加,使得换热管的强化换热效果降低,而当换热管的扁平度过小时,努塞尔数Nu和压降△P变化缓慢,对换热管的强化换热影响较弱,所以扁平度n的最佳选择是0.7~1.4。 相似文献
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螺旋隔板换热器的研究现状及应用 总被引:1,自引:0,他引:1
螺旋隔板换热器主要包括两种不同类型的结构形式,即没有中心管的非整体连续的螺旋隔板换热器和有中心管的整体连续的螺旋隔板换热器.总结了国内外学者对螺旋隔板换热器所做的主要研究工作,包括壳程流体的动力学研究、传热与压降性能研究和数值模拟,并介绍了整体连续型螺旋隔板强化管换热器在工业中的应用.最后,对螺旋隔板换热器的下一步研究工作进行了展望. 相似文献
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为解决汽车空-空中冷器冷却扁管最优换热性能的问题,运用FLUENT软件,建立了4种不同断面结构的冷却扁管导热和管内流动换热耦合数学模型,采用CFD方法对该传热问题进行了数值模拟计算.将数值计算的传热努塞尔特数与Gnielinski传热关联式、摩擦因子f与Webb实验关联式、Filonenko经验公式、Blasius关联式进行了对比;良好的结果吻合性验证了数值计算方法的正确性;通过4种冷却扁管换热因子j和流动摩擦因子f的对比分析,提出了冷却扁管综合性能的评价方法(jlf)1/3.研究结果表明,采用无量纲因子(jlf)1/3方法评价口琴式冷却扁管具有最优换热性能,斜撑式冷却扁管次之,从而可为汽车空-空中冷器结构设计或匹配选型提供重要的理论依据. 相似文献
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《机械工程与自动化》2017,(6)
为了提高国产大流量除冰液加热系统的效率,选择系统中的主要加热元件光滑螺旋盘管(简称光滑盘管)进行优化。优化方法是螺旋盘管管壁向内凸起形成环形肋,新管称为横纹螺旋盘管(简称横纹盘管)。采用数值模拟研究了横纹螺旋盘管的传热特性,结果表明:横纹盘管比光滑盘管传热性能更好,当环形肋深度在0.05D~0.075 D(D为管截面直径)范围时,横纹盘管传热强化效果较优。 相似文献
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横纹槽管内插扭带复合强化传热的试验研究* 总被引:1,自引:0,他引:1
不同强化传热方式的复合会产生不同的传热效果,通过试验将不同扭率的扭带与同一规格横纹槽管复合强化传热的效果进行对比。试验以高黏度的导热油为工质,在500<Re <7 000、50<Pr <180的参数范围内,研究复合强化管的Nu 数和阻力系数f 随着Re 数的变化情况,通过多元线性回归得到Nu 数和f 的关联式,并以强化传热性能评价指标(Performance evaluation criteria,PEC)值为标准评价其综合换热性能。结果表明:相同扭率下,复合强化管的阻力系数是光管内插扭带阻力系数的2~5倍,Nu 数是光管内插连续扭带的1~4倍。随着Re 数的增加,扭率Y 对复合强化管的Nu 数值影响越来越小。层流工况下,复合强化管的综合换热性能指标PEC值随Re 数的增加而增加,且与扭率Y 成负相关;过渡流工况下,复合强化管的PEC值都随Re 数的增加而减小,扭率Y 为5.21时的复合强化管综合换热效果最好。 相似文献
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搭建了扭曲管闭式冷却塔的换热实验平台,在空冷模式下通过测试在不同风机频率以及风机频率固定时不同的管内流体进口温度、空气干球温度情况下闭塔的传热性能、流动阻力和能耗,得到了风机频率、管程体积流量以及管程进口温度、环境温度对综合传热性能和空冷传热量的影响,进而得出优化闭塔空冷换热的方式,并推导出在不同的季节温度下最合理的运行方式。同时本试验拟合了风机频率和风机功率等与迎面风速的试验关联式以及空冷管外空气的传热系数试验关联式,对扭曲管式闭式冷却塔的优化设计有一定的指导作用。 相似文献
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A. Kalendar T. Galal A. Al-Saftawi M. Zedan 《Journal of Mechanical Science and Technology》2011,25(8):1969-1977
Existing MSF systems experience severe mechanical difficulties due to fouling deposited inside the bore of the condenser tubes.
The idea of replacing smooth tubing with enhanced tubing is discussed for innovative design. Performance analysis between
enhanced and plain tubes is investigated experimentally, using a simulated design test rig. The study is performed for corrugated
and smooth resemblance aluminum-brass tubes of 1100 mm length and 23 mm bore. Pumping different coolants as steady transition/turbulent
flow, fresh water and authentic brine are conducted to simulate actual environmental conditions. Three different flow velocities
are examined: 0.1, 0.1645, and 0.2398 m/s. Comparing results of the brine with that of fresh water shows the effects of fouling
on significantly lowering values of overall heat transfer coefficient versus time. The results confirm that the smooth tube
has a greater fouling tendency than the corrugated tube. The effect of fouling is reduced as flow speed increases, and consequently,
the asymptotic value of overall heat transfer coefficient U* increases. Values of U* for the enhanced tube are much higher
than that of the smooth tube. The highest difference occurs at velocity 0.2398 m/s by a factor of about 1.5. Overall, by utilizing
real brine, the results proved that heat performance of the employed corrugated tube is superior to the plain, over the studied
time period, 140 hrs, and on the studied range of flow speeds. 相似文献
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Samchul Ha 《Journal of Mechanical Science and Technology》2000,14(5):537-546
The heat transfer characteristics of refrigerant-oil mixture for horizontal in-tube evaporator have been investigated experimentally.
A smooth copper tube and a micro-fin tube with nominal 9.5 mm outer diameter and 1500 mm length were tested. For the pure
refrigerant flow, the dependence of the axial heat transfer coefficient on quality was weak in the smooth tube, but in the
micro-fin tube, the coefficients were 3 to 10 times greater as quality increases. Oil addition to pure refrigerant in the
smooth tube altered the flow pattern dramatically at low mass fluxes, with a resultant enhancement of the wetting area by
vigorous foaming. The heat transfer coefficients of the mixture for low and medium qualities were increased at low mass fluxes.
In the micro-fin tube, however, the addition of oil deteriorates the local heat transfer performance for most of the quality
range, except for low quality. The micro-fin tube consequently loses its advantage of high heat transfer performance for an
oil fraction of 5%. Results are presented as plots of local heat transfer coefficient versus quality. 相似文献