论文部分内容阅读
电渗流通过外加电场来驱动液体通过微小通道,同时由于焦耳热效应的存在,也会在流体及通道表面形成热传导现象。应用计算流体力学方法,对矩形发散形微通道内电渗流流动所产生的流场、温度场进行了数值模拟和研究。由于流体的介电常数、电导率、粘性、热导率等属性依赖于温度的变化,焦耳热效应产生的温度场会改变流体的多种属性,并进而影响到流动速度、压力分布等。计算结果表明,焦耳效应在微管道芯片上产生了一个非均匀的热梯度场,并同时影响液体流动。热梯度场的存在在均匀截面通道内可以提高液体的流动速度,但在发散形通道内却不能产生相似的效果,此时的出口速度和体积流速都明显下降,分别达到约16 %和60μl/ min。焦耳热效应同时通过降低流速和流动压力减弱了发散形管道的电渗流泵送性能。
Electroosmotic flow drives the liquid through the tiny channels by the application of an electric field. At the same time, due to the Joule heating effect, the heat conduction phenomenon also occurs on the surface of the fluid and the channel. The computational fluid dynamics (CFD) method was used to simulate and study the flow field and temperature field of the electroosmotic flow in a rectangular divergent microchannel. Due to the dielectric constant, conductivity, viscosity, thermal conductivity and other properties depend on the temperature change, the temperature field caused by the Joule heating effect will change a variety of fluid properties, and thus affect the flow rate, pressure distribution and so on. The calculated results show that the Joule effect produces a non-uniform thermal gradient field on the microchip chip and simultaneously affects the liquid flow. The presence of a thermal gradient field can increase the liquid flow rate in a uniform cross-section channel, but does not produce similar effects in the divergent channel. At this time, both the exit velocity and the volume flow rate are significantly reduced to about 16% and 60 μl / min. The Joule heating effect also attenuates the electroosmotic flow pumping performance of divergent ducts by reducing flow rate and flow pressure.