Periodic laminar flow and heat transfer in square channel

doi:10.3969/j.issn.0438-1157.2013.05.006

Abstract

Abstract: A numerical investigation is conducted to examine laminar periodic flow and heat transfer characteristics in a square channel fitted with 45? inclined baffle inserted periodically in the channel.Air is the working fluid with the flow rate in terms of Reynolds number based on the channel hydraulic diameter ranging from 100 to 1000.The utilization of the 45? inclined baffles is to create counter-rotating vortex flows having a significant influence on the flow laminar intensity, enhancing heat transfer in the channel.Effects of different pitch ratios(PR=L/H)with a baffle height ratio(BR=b/H)of 0.2 on heat transfer and pressure loss in the channel were examined.The results show that the baffles create pair of vortex flows, inducing impingement flows on a side and the upper and lower walls and increasing heat transfer rate over the test channel substantially.An analysis on the averaged Nusselt number ratio, friction factor ratio and thermal enhancement factor with the change of pitch ratio and Reynolds number is used for establishing the corresponding criterion correlation.The computation reveals that the optimum thermal performance enhancement factor of about 3.0 is found at PR=0.5.

Key words: periodic flow, channel, laminar flow, heat transfer

摘要： 应用数值模拟方法分析了以周期性方式布置不同节距比(PR=L/H)、倾角为45°挡板槽道的流动特性与传热特性。挡板在槽道上下壁面对齐布置高度比(BR=b/H)为0.2,以便在槽道内部形成一对沿流向的反向旋涡。数值模拟计算Reynolds数范围为100~1000,流体介质为空气。计算结果表明:布置斜置挡板后,在槽道内诱导产生了沿流向的旋涡流,且在测试段中旋涡流冲击槽道上下壁面和槽道一侧壁面,结果使得传热效率提高;分析了范围内平均Nusselt数比Nu/Nu₀、摩擦系数比f/f₀及传热增强系数η随节距比PR和Reynolds数的变化关系,并建立了相应的准则关系式;当挡板间节距比为0.5时,传热增强系数可达最大值3.0。

关键词: 周期性流动, 槽道, 层流, 传热

CLC Number:

TK124

WANG Jiansheng, XU Yong. Periodic laminar flow and heat transfer in square channel[J]. CIESC Journal, 2013, 64(5): 1541-1548.

汪健生, 徐勇. 三维槽道的周期性层流流动与传热[J]. 化工学报, 2013, 64(5): 1541-1548.

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