Abstract Experimental results of isothermal pressure drop and convective heat transfer coefficient are presented for a smooth tube with tri-orifice baffle inserts, under net and oscillatory flow conditions. Using propylene-glycol as working fluid, net Reynolds numbers in the range R e n = 10 − 600 are reproduced, allowing to describe Fanning friction factor in the laminar, transitional and turbulent regimes, with an onset of transition at R e n ≈ 100 in steady-state conditions. Oscillatory Fanning friction factor for 20 R e o s c 200 is also reported, based on the maximum oscillatory pressure drop obtained by statistical fitting of the signal. Nusselt number under uniform heat flux conditions is obtained for superimposed net and oscillatory flows in the ranges 10 R e n 600 and 10 R e o s c 440 , with Prandtl number in the range 190 P r 470 . The existence of buoyancy effects in steady-state conditions and its vanishing with oscillations is analyzed. The oscillatory flow promotes a 4-fold increase of heat transfer for R e n 20 . For R e n > 100 , the effect of the flow oscillation on heat transfer enhancement is negligible.

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三孔挡板圆管中振荡流动摩擦和传热的实验相关性

摘要 给出了带有三孔挡板插入件的光滑管在净流和振荡流条件下的等温压降和对流传热系数的实验结果。使用丙二醇作为工作流体，可以重现 R en = 10 - 600 范围内的净雷诺数，从而可以描述层流、过渡和湍流状态下的范宁摩擦系数，在稳定的 R en ≈ 100 处开始过渡-状态条件。基于通过信号的统计拟合获得的最大振荡压降，还报告了 20 Reosc 200 的振荡扇形摩擦系数。对于在 10 R en 600 和 10 R eosc 440 范围内的叠加净流和振荡流，获得均匀热通量条件下的 Nusselt 数，其中 Prandtl 数在 190 P r 470 范围内。分析了稳态条件下浮力效应的存在及其随振荡的消失。振荡流促进了 R en 20 的传热增加了 4 倍。对于 R en > 100 ，流动振荡对传热增强的影响可以忽略不计。