On the measurement and analysis of data from transient heat transfer experiments
On the measurement and analysis of data from transient heat transfer experiments
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DOI：
10.1016/j.ijheatmasstransfer.2016.03.009
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发表时间：
2016-07
影响因子：
5.2
通讯作者：
Geonhwan Cho;Hui Tang;J. Owen;G. Lock
中科院分区：
文献类型：
--
作者：
Geonhwan Cho;Hui Tang;J. Owen;G. Lock
本文介绍了一种由试件表面温度的瞬时测量确定换热系数h和绝热表面温度Tad的新方法。最大似然估计(MLE)与傅立叶一维方程结合使用，无需测量气温，即可确定h和Tad的最佳值以及它们的95%可信区间。验证实验是在专门建造的小型风洞中进行的，并使用了一种新型的红外(IR)传感器来测量试件的表面温度。网状加热器被用来产生空气温度的阶跃变化或“慢瞬变”，在这种情况下，空气温度--以及由此产生的温度--随时间缓慢增加。利用“噪声数据”进行的数值模拟表明，对于阶跃变化和慢瞬变情况，计算都给出了准确的h和Tad估计。由风洞测量得到的h和Tad值与平板湍流的经验关联式符合得很好。这种新方法的一个优点是，它可以用于所有的瞬变实验，即使是那些违反半无限固体假设的慢瞬变实验，这是大多数现有分析方法中使用的假设。这种新方法适用于只有一股流体的边界层流动，也可以应用于涉及两股流体的气膜冷却等三个温度问题。用这种方法解决这些问题的显著优点是，一次实验就可以准确地测定h和Tad。
This paper describes a new method to determine the heat transfer coefficient, h, and the adiabatic-surface temperature, T ad, from transient measurements of the surface temperature of a test piece. Maximum Likelihood Estimation (MLE) is used in conjunction with Fourier’s 1D equation to determine the optimum values of h and T ad, and also their 95% confidence intervals, without having to measure the air temperature. Validation experiments are conducted in a small purpose-built wind tunnel, and a novel infra-red (IR) sensor is used to measure the surface temperature of the test piece. A mesh heater is used to generate either a step-change in the air temperature or a ‘slow-transient’in which the air temperature–and consequently T ad–increases slowly with time. Numerical simulations, using ‘noisy data’, show that the computations give accurate estimates of h and T ad for both the step-change and slow-transient cases. The values of h and T ad determined from the measurements in the wind-tunnel are in good agreement with empirical correlations for turbulent flow over a flat plate. An advantage of the new method is that it can be used for all transient experiments, even those slow transients that violate the assumption of a semi-infinite solid, an assumption that is used in most existing analysis methods. The new method, which was applied here to boundary-layer flow with one stream of fluid, could also be applied to ‘three-temperature problems’, like film cooling, which involve two streams of fluid. The significant advantage of using the method for these problems is that both h and T ad could be determined accurately from a single experiment.