Thermal transpiration pumping in multistage assemblies is computationally investigated. Each stage is formed by combining in series-long microchannels with (a) uniform–uniform (“uni–uni”), (b) converging–uniform (“con–uni”), (c) diverging–uniform (“div–uni”) and (d) converging–diverging (“con–div”) rectangular cross sections. In all four investigated assemblies the generated pressure difference with the associated mass flow rate is fully assessed, in terms of inlet pressure, inclination parameter and number of stages. The analysis is based on linear kinetic modeling and is valid in the whole range of gas rarefaction. It is concluded that the “con–uni” and “div–uni” assemblies provide higher pressure differences and lower mass flow rates than the “uni–uni” assembly and they may be more suitable for specific pumping applications. The characteristics of the “con–uni” and “div–uni” assemblies are very close to each other. The multistage “uni–uni”, “con–uni” and “div–uni” assemblies are more stable when operating at small inlet pressures, where the pressure difference remains almost constant in wide ranges of mass flow rate. It is advisable to add as many stages as possible to increase, depending on the application, either the pressure difference or mass flow rate or both. Furthermore, the “con–div” assembly provides smaller pressure differences and mass flow rates than the other three, but it is suitable for diode applications. It is characterized by the so-called blocking inlet pressure, where the deduced pressure difference in the converging and diverging channels is the same. A detailed parametrization of the blocking inlet pressure in terms of inclination ratio, mean height, temperature difference and gas species, has been performed. It is concluded that multistage “con–div” assemblies may be ideally applied as thermally driven microfluidic diodes to control or block the flow, as well as to separate the species in multicomponent gas mixtures.

对多级组件中的热蒸发泵进行了计算研究。每个阶段都是通过将一系列串联的微通道与（a）均匀均匀（“ uni-uni”），（b）收敛均匀（“ con-uni”），（c）分散均匀（“ div- uni”）和（d）会聚-发散（“ con-div”）矩形横截面。在所有四个被研究的组件中，根据入口压力，倾角参数和级数充分评估了产生的压力差以及相关的质量流量。该分析基于线性动力学模型，并且在整个气体稀化范围内均有效。结论是，“ con-uni”和“ div-uni”组件比“ uni-uni”组件提供更高的压差和更低的质量流率，它们可能更适合于特定的泵送应用。“ con-uni”和“ div-uni”程序集的特性非常接近。多级“ uni-uni”，“ con-uni”和“ div-uni”组件在较小的入口压力下运行时更加稳定，在较大的质量流量范围内，压力差几乎保持恒定。建议根据应用增加尽可能多的级数，以增加压差或质量流率，或两者兼而有之。此外，“ con-div”组件提供的压力差和质量流率比其他三个组件小，但它适用于二极管应用。其特征在于所谓的阻塞入口压力，其中，在会聚和发散通道中推导的压差相同。根据倾斜比详细描述了阻塞入口压力的参数，平均高度，温度差和气体种类已执行。结论是，多级“ con-div”组件可以理想地用作热驱动微流体二极管，以控制或阻止流量，以及分离多组分气体混合物中的物质。