Abstract To predict the heat transfer enhancements that result from the application of a pulsating flow in a pipe, we experimentally investigated the turbulent heat transfer variations produced in response to sudden accelerations or decelerations to flows within a pipe. To accomplish this, the Reynolds numbers with the valve open (Re1) and close (Re0) were systematically varied in the range of 8,000 ≤ Re1 ≤ 34,000 and 700 ≤ Re0 ≤ 23,000, respectively, and in-pipe spatiotemporal heat transfer variations were measured using infrared thermography simultaneously with temporal variations to the in-pipe flow properties. Based on the experimental results, it was found that the heat transfer delays that occur in response to accelerations or decelerations can be characterized using the corresponding time lag Δt and first-order time constant τ. The values of Δt and τ can be expressed as non-dimensional forms of Δt/(ν/uτ2) and τ/(R/uτ), respectively, where uτ is the pipe wall friction velocity, ν is the kinematic viscosity of the fluid, and R is the pipe radius.

中文翻译：

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湍流传热对管道中流动的加速或减速的响应延迟

摘要 为了预测由于脉动流在管道中的应用而导致的传热增强，我们通过实验研究了响应于管道内流动的突然加速或减速而产生的湍流传热变化。为此，阀门打开 (Re1) 和关闭 (Re0) 时的雷诺数分别在 8,000 ≤ Re1 ≤ 34,000 和 700 ≤ Re0 ≤ 23,000 的范围内系统地变化，并测量了管道内的时空传热变化同时使用红外热像仪和管道内流动特性的时间变化。根据实验结果，发现响应于加速或减速而发生的传热延迟可以使用相应的时滞 Δt 和一阶时间常数 τ 来表征。