Mechanism and transmission characteristics of micropump thermal equilibrium evolution under thermal transpiration effect

Abstract A micropump without moving parts can achieve the transmission and pressurization of hydrogen in microfluidic systems under the thermal transpiration effect. The flow mechanism and transmission characteristics of the micropump thermal equilibrium evolution are pivotal in determining pressure difference response and transmission stability, which are the theoretical basis for guiding the design of an efficient and stable micropump. In this paper the validity of the flow model is verified by the experiments. The flow and pressurization mechanisms of the thermal equilibrium evolution under the effects of the development and coupled evolution of three types of flows, as well as the effect laws of structural characteristics and operating parameters on transmission characteristics were studied. Research has shown that thermal equilibrium evolution includes four stages. In the first stage, the flow is dominated by thermal expansion flow, and the pressure difference rapidly increases from 0 Pa to 7880 Pa. In the second stage, the flow transitions to being dominated by the Poiseuille flow, with both the pressure difference and the intensity of the Poiseuille flow gradually decreasing over time. In the third stage, the Poiseuille flow and pressure difference decrease, while the thermal transpiration flow increases. In the fourth stage, the Poiseuille flow and the thermal transpiration flow reach a dynamic equilibrium under a pressure difference of 651 Pa. As the microchannel length, operating temperature difference, operating pressure increase and the microchannel diameter decreases, the thermal equilibrium evolution time increases, which weakens the stability of the micropump. The research results provide theoretical and technical support for the operation, design, and application of an efficient and stable micropump.