Hydrodynamic Study of High Speed Flow and Heat Transfer Through a Microchannel

Abstract

Fluid flow and heat-transfer characteristics in microchannels are investigated using a finite element based hydrodynamic model with first-order slip/jump boundary conditions. Helium and nitrogen are utilized as working fluid, and the Knudsen-number ranges from slip to transition regime. Results for high-speed compressible gas flow for two separate cases for a microchannel with rough surface and an aspect ratio of five have been compared with published direct-simulation Monte Carlo results. Despite some noticeable differences, the hydrodynamic model compares favorably in predicting the flow structure and heat-transfer characteristics for high-speed microflows. NomenclatureC p = specific heat at constant pressure H = height of the channel Kn = Knudsen number k = thermal conductivity L = length of the channel Ma = Mach number P = gas pressure Pr = Prandtl number R = reduced gas constant T = temperature t = time u = gas velocity in x direction v = gas velocity in y direction γ = specific heat ratio = reference length λ = mean free path of the fluid µ = coefficient of viscosity ρ = gas density σ T = thermal-momentum coefficient σ v = tangential-momentum coefficient Subscripts g = gas properties w = wall properties 0 = reference quantity

Finite Volume Simulation of Supersonic to Hypersonic Gas Flow and Heat Transfer through Microchannels

“…The maximum value of the near wall temperature reaches 662 K, which is sufficiently close to the DSMC prediction by Liou and Fang [3]. The gradual rise in the centerline temperature also goes hand in hand with the DSMC prediction reported in [3] and [4]. The predicted exit centerline temperature is 712 K. The FV prediction for the centerline temperature appears to be a little higher in comparison with the DSMC results [3] near the exit region.…”

“…DSMC results presented in [3] show a decrease in the centerline temperature near the exit of the microchannel. The FEM prediction reported in [4] shows a negative deviation from the DSMC result [3]. Fig.…”

“…1 summarizes the length (L: y axis), height (H: z axis) and other conditions for the corresponding test cases. For a high speed flow simulation, 10 % of the channel near the entrance region is kept as a specular reflector, in order to maintain similar conditions to those stated in the literature [3][4][5]. The inlet temperature and pressure are kept at 300 K and atmospheric, respectively.…”

“…Liou and Fang [3] studied the effect of the Knudsen number on the heat transfer in microchannels using DSMC. Raju and Roy [4] compared the Finite Element (FE) solution of high speed gas flow in microchannels with the DSMC results of Liou and Fang [3]. The effect of the Knudsen number, gas species and wall temperature distribution on supersonic gas flow was studied by Le and Hassan [5] using DSMC.…”

Numerical Study of Fluid Flow and Heat Transfer in Partially Heated Microchannels Using the Explicit Finite Volume Method

“…The local Knudsen number is a measure of the degree of rarefaction of gases encountered in MEMS devices. Popular methods for analyzing the heat transfer characteristics of gases in microchannels include the particulate method of Boltzmann equations, Direct Solution Monte Carlo (DSMC) and Burnett equation models [4]. Several investigators have used the DSMC approach where the Knudsen number is very high, which involves a high computation cost and time requirement.…”