Performance of MEMS-based nozzles at moderate and low temperatures is numerically analyzed using the direct simulation Monte Carlo method. Considering the intermolecular attractive potential due to low temperature, the generalized soft sphere collision model is introduced. The Larsen-Borgnakke model for the generalized sphere model is used to model the energy exchange between the translational and internal modes. The results for nozzle flows at an initial temperature of 300 K show that the temperature behind the throat is quite low and the intermolecular attractive potential cannot be ignored. Different working conditions in two-dimensional nozzles are simulated using the present method, including exit pressure, inlet pressure, initial temperature, nozzle geometry, and gas species. The effect factors on the nozzle performance are analyzed. A 3D nozzle flow simulation shows the increased surface-to-volume ratio which leads to high viscosity dissipation cause a much lower flow characteristic and performance comparing with the 2D case.

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