The current experimental study investigates the effects of installing three types of fluidic oscillators—feedback-free, single-feedback loop and two-feedback channel—on thermal performance of a single-pipe heat exchanger. Results are presented as Nusselt number and friction coefficient at the Reynolds number range of 5600–16,400 and two surface thermal conditions: (a) constant continuous heat flux (CCHF) and (b) constant periodically interrupted heat flux (CPIHF). All the three fluidic oscillators have the same square exit throat with the length of 5.67 mm and the same outer diffuser with the depth of 5.67 mm and 45° diverging angle which overlap the tube’s inner diameter. In the case of CCHF, up to 37%, 83%, and 23% heat transfer enhancement are observed for feedback-free, single-feedback loop and two-feedback channel fluidic oscillators, respectively. In the case of CPIHF, feedback-free and two-feedback channel fluidic oscillators showed no merit relative to the plain tube, but single-loop feedback fluidic oscillator still gives up to 57% thermal performance enhancement. Since fluidic oscillators are no-moving-part devices capable of generating self-induced self-sustained oscillating flows, the current study indicates the high capability of the fluidic oscillators for the passive heat transfer enhancement of heat exchangers.

中文翻译：

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带流体振荡器的单管热交换器中的传热增强

当前的实验研究调查了安装三种类型的流体振荡器（无反馈，单反馈回路和双反馈通道）对单管热交换器的热性能的影响。结果表示为在5600–16,400的雷诺数范围和两个表面热条件下的努塞尔数和摩擦系数：（a）恒定连续热通量（CCHF）和（b）恒定周期性中断热通量（CPIHF）。这三个流体振荡器都具有相同的方形出口，长度为5.67毫米，相同的外部扩散器，深度为5.67毫米，扩散角为45°，与管的内径重叠。在CCHF的情况下，对于无反馈，单反馈回路和两反馈通道流体振荡器，传热提高了37％，83％和23％，分别。对于CPIHF，无反馈和两反馈通道流体振荡器相对于普通管没有任何优点，但是单环反馈流体振荡器仍可提供高达57％的热性能增强。由于流体振荡器是能够产生自感应的自持振荡流的固定部件，因此当前的研究表明，流体振荡器具有很高的热交换器被动传热能力。