In order to better understand thermal transpiration, geometric coefficient (LND) and reduction ratio of net mass flow (ΨM) were defined to study pressure difference variation and net mass flow of 13 gases under thermal transpiration effects with different microchannel structures, gas properties, flow regimes and temperatures. The results indicate that the net mass flow decreases rapidly with the increase of Knudsen number (Kn) and LND, and it reduces by 99% at Kn ≈ 2.4 or LND ≈ 1000. In the transitional flow regime, the net mass flow of most non-polar gases is higher than those of polar gases, and lower viscosity index results in higher net mass flow. In the free molecular flow regime, the gas with larger molecular mass or viscosity results in higher net mass flow. The pressure difference enlarges with the increase of Kn in the transitional flow regime and approaches to a constant maximum in the free molecular flow regime, which is ~17.8% higher than the peak in the transitional flow regime. Moreover, the net mass flow and pressure difference increase approximately by 18% and 15% respectively with every 10 K rise of temperature difference. The temperature difference has stronger effects on net mass flow of gas with larger viscosity indices in the transitional flow regime. Suitable flow regime and microchannel structure should be determined according to practical requirements due to the coupling effects between microchannel dimension and flow regime. Suggestions are given for applications based on thermal transpiration effects.%为深刻认识热流逸现象,引入几何系数和净质量流量减少率,研究了13种气体在热流逸效应下压差和净质量流量与微通道结构尺寸特征、气体特性、流动领域及温差等因素的关系.结果表明,净质量流量随努森数与几何系数的增大迅速衰减,当努森数达2.4左右或几何系数达1000左右时均减少99%;在过渡流领域大部分非极性分子气体的净质量流量高于极性分子气体,且黏性指数较小的气体其净质量流量较大;在自由分子流领域,分子质量较大或黏性较大的气体其净质量流量较大.压差在过渡流领域随努森数增大而增大,当流态进入自由分子流领域后达到最大值并恒定,且较过渡流领域的峰值高约17.8%.温差每升高10 K,净质量流量与压差分别平均增大约18%和15%,且在过渡流领域,气体的黏性指数越大其净质量流量受温差的影响就越大.因微通道尺寸与气体流态相互耦合,故应视压差或流量的具体需求来确定适宜的流态与微通道结构.指出了热流逸效应若干应用需侧重考虑的要点.
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