A Stepped-Bar Apparatus for Thermal Resistance Measurements
A Stepped-Bar Apparatus for Thermal Resistance Measurements
复制标题
用于热阻测量的阶梯棒装置
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
B. Cola
中科院分区：
文献类型：
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作者：
Dakotah Thompson;S. R. Rao;B. Cola
设计并建造了一种阶梯杆装置，用于使用稳态传热技术表征材料的热阻。该装置的设计是ASTM D5470标准的修改，其中使用相等横截面积的参考棒来外推未知热阻的样品的表面温度和热通量。设计修改涉及有意地使设备的上部参考杆（URB）尺寸过大，以避免由于参考杆未对准而导致的接触面积不确定性，这是难以解释的，以及可能与为设备配备精确对准控制（例如，气动对准）。使用数值模拟，预计在样品界面附近的上部参考栏的多维热传递。通过拟合通过样品界面附近的热电偶读数的二阶回归线来解释上部参考条中产生的非线性温度曲线。市售的热间隙垫和热膏的热阻进行了测量与步进杆装置，测量值与公布的结果吻合良好，并表现出高度的再现性。标准装置和阶梯杆装置的测量不确定度随热电偶精度的提高而降低。值得注意的是，由于参考杆与标准装置的不对准而导致的不确定性随着热电偶精度和热电偶数量的增加而变得更加明显，这表明阶梯杆装置对于实现非常低的热阻的准确、高精度测量将是特别有利的。[DOI：10.1115/1.4025116]
A stepped-bar apparatus has been designed and constructed to characterize the thermal resistance of materials using steady-state heat transfer techniques. The design of the apparatus is a modification of the ASTM D5470 standard where reference bars of equal cross-sectional area are used to extrapolate surface temperatures and heat flux across a sample of unknown thermal resistance. The design modification involves intentionally oversizing the upper reference bar (URB) of the apparatus to avoid contact area uncertainty due to reference bar misalignment, which is difficult to account for, as well as the high cost that can be associated with equipping the apparatus with precise alignment controls (e.g., pneumatic alignment). Multidimensional heat transfer in the upper reference bar near the sample interface is anticipated using numerical modeling. The resulting nonlinear temperature profile in the upper reference bar is accounted for by fitting a second order regression line through thermocouple readings near the sample interface. The thermal resistances of commercially available thermal gap pads and thermal pastes were measured with the stepped-bar apparatus; the measured values were in good agreement with published results, and exhibited a high degree of reproducibility. The measurement uncertainty of both the standard and stepped-bar apparatus decrease with increased thermocouple precision. Notably, the uncertainty due to reference bar misalignment with the standard apparatus becomes more pronounced as thermocouple precision and the number of thermocouples increases, which suggests that the stepped-bar apparatus would be especially advantageous for enabling accurate, high-precision measurements of very low thermal resistances. [DOI: 10.1115/1.4025116]