Thermal conductivity measurement of liquids in a microfluidic device
Thermal conductivity measurement of liquids in a microfluidic device
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DOI：
10.1007/s10404-010-0652-x
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发表时间：
2011
影响因子：
2.8
通讯作者：
D. Kuvshinov;M. Bown;J. Macinnes;R. Allen;R. Ge;L. Aldous;C. Hardacre;N. Doy;M. Newton;G. McHale
中科院分区：
文献类型：
--
作者：
D. Kuvshinov;M. Bown;J. Macinnes;R. Allen;R. Ge;L. Aldous;C. Hardacre;N. Doy;M. Newton;G. McHale
开发了一种新的基于微流体的液体热导率测量方法，以满足许多实际应用中使用小（微升）样品尺寸进行测量并集成到紧凑设备中的要求。该方法还提供了高通量测试的可能性。电阻加热器和温度传感器被集成到玻璃微流体芯片中，以允许传输和检测穿过样品薄层的平面热波。该装置的设计使得热传递在短时间内是局部一维的。这使得检测到的温度瞬变可以分为两个不同的组成部分：一个短时、纯一维部分，可以从中确定样本热导率；另一个长时间部分包含三维和周围热储层有限尺寸的影响。一维成分的识别产生稳定的温差，由此可以确定样品的热导率。需要进行校准才能正确表示随温度变化的加热器电阻、系统层厚度和固体材料热导率。在这项初步研究中，在大气压力和 30–50°C 的温度范围内测量甲醇/水混合物。结果表明，在测试的热导率和温度范围内，该装置的测量精度在2.5%以内。推导了测量不确定度与系统的几何和热特性之间的关系，并用于确定进一步减少误差的方法。
A new microfluidic-based approach to measuring liquid thermal conductivity is developed to address the requirement in many practical applications for measurements using small (microlitre) sample size and integration into a compact device. The approach also gives the possibility of high-throughput testing. A resistance heater and temperature sensor are incorporated into a glass microfluidic chip to allow transmission and detection of a planar thermal wave crossing a thin layer of the sample. The device is designed so that heat transfer is locally one-dimensional during a short initial time period. This allows the detected temperature transient to be separated into two distinct components: a short-time, purely one-dimensional part from which sample thermal conductivity can be determined and a remaining long-time part containing the effects of three-dimensionality and of the finite size of surrounding thermal reservoirs. Identification of the one-dimensional component yields a steady temperature difference from which sample thermal conductivity can be determined. Calibration is required to give correct representation of changing heater resistance, system layer thicknesses and solid material thermal conductivities with temperature. In this preliminary study, methanol/water mixtures are measured at atmospheric pressure over the temperature range 30–50°C. The results show that the device has produced a measurement accuracy of within 2.5% over the range of thermal conductivity and temperature of the tests. A relation between measurement uncertainty and the geometric and thermal properties of the system is derived and this is used to identify ways that error could be further reduced.