Simulation of rarefied gas flow and heat transfer in microchannels

2002 ◽  
Vol 45 (3) ◽  
pp. 321 ◽  
Author(s):  
Xian WANG
Keyword(s):  
Heat Transfer ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Rarefied Gas Flow ◽  
Flow And Heat Transfer

Experimental study of heat transfer in rarefied gas flow in a circular tube with constant wall temperature

2018 ◽  
Vol 93 ◽  
pp. 326-333 ◽  
Author(s):  
Vadiraj Hemadri ◽  
G.S. Biradar ◽  
Nishant Shah ◽  
Richie Garg ◽  
U.V. Bhandarkar ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Wall Temperature ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Circular Tube ◽  
Rarefied Gas Flow ◽  
Constant Wall Temperature

Study of Temperature and Velocity Distribution of Rarefied Gas Flow in Micro-Nano Channels

2009 ◽  
Author(s):  
Hadi Ghezel Sofloo ◽  
Alireza Shams ◽  
Reza Ebrahimi
Keyword(s):  
Heat Transfer ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Direct Simulation Monte Carlo ◽  
Ideal Gas ◽  
Gas Density ◽  
Channel Size ◽  
Flow And Heat Transfer ◽  
Nonideal Gas ◽  
Gas Effect

This paper deals with simulation of transport phenomena in micro and nano pores. The number of cavities and the cavity radius were estimated by using Henry’s law for adsorption of Argon onto ZSM-5 and NaX zeolites. This work showed both of zeolites have pores with average size less than 1 nm. Then with using micro-nano channel assumption instead of micro-nano pores, gas flow and heat transfer were investigated. Subsonic nonideal gas flow and heat transfer for different Knudsen number are investigated numerically using the Direct Simulation Monte Carlo method modified with a consistent Boltzamnn algorithm. The collision rate is also modified based on the Enskog theory for dense gas. It is shown that nonideal gas effect becomes significant when the gas becomes so dense that the ideal gas assumption breaks down. The results also show that the nonideal gas effect is dependent not only on the gas density, but also the channel size. A higher gas density and a smaller channel size lead to a more significant nonideal gas effect. The nonideal gas effect also causes lower skin friction coefficients and different heat transfer flux distributions at the wall surface.

The Simulations of Flow and Heat Over Microscale Sensors in Supersonic Rarefied Gas Flows Using DSMC

2016 ◽  
Author(s):  
Masoud Darbandi ◽  
Ghasem Mosayebi
Keyword(s):  
Heat Flux ◽  
Nusselt Number ◽  
Knudsen Number ◽  
Surface Heat Flux ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Surface Heat ◽  
Rarefied Gas Flow ◽  
Transitional Regime ◽  
Flow And Heat Transfer

As the use of MEMS-based devices and systems are continuously increasing, the understanding of their correct characteristics becomes so serious for the related researches. In this study, the supersonic rarefied gas flow over microscale hotwires is investigated using the Direct Simulation Monte Carlo (DSMC) method. Indeed, the DSMC has been accepted as a powerful method to study the rarefied gas flow especially in transitional regime. Therefore, it can be considered as a reliable method to investigate the rarefied supersonic flow over microscale objects including the microscale hotwires. In this work, we study the effective parameters, which affect the performance of these sensors at constant sensor surface temperature conditions. We use our developed DSMC code to perform our investigation. This code uses the DSMC algorithm to solve the rarefied gas flow on unstructured grid distributions. To validate our developed DSMC code, we solve the supersonic rarefied gas flow and heat transfer in microchannel considering different Knudsen number magnitudes. Comparing the achieved flow and heat transfer solutions with other available results and data reported on microchannel studies, we verify the accuracy of achieved results. Next we focus on hotwire sensor, which often consists of the combinations of different long narrow circular cylinders. We study the effects of grid resolution, time step size, and the number of simulated particles on the obtained results. We further study the effects of sensor temperature and sensor diameter on the sensor thermal performance. The achieved results indicate that the surface heat flux performs very similarly in different studied cases. For example, the achieved local Nusselt number distributions around the circular sensor show that the surface heat flux would gradually increase from the sensor stagnation point to its rear end as the temperature gradient increases. It reaches to a maximum magnitude and it then starts decreasing resulting in effective heat flux reduction. Finally, there is a low pressure zone at the rear side of cylinder, which is not considerably affected by the flow properties. The results also show that if the wire surface temperature increases, the Nusselt number would reduce. However, the amount of Nusselt Number reduction rate would decrease as the temperature increases. Furthermore, the results show that the Reynolds number decreases and the Knudsen number increases as the sensor diameter decreases, which is due to the transitional regime behavior. As is known, the flow at boundaries change the condition from the slip to transitional regime when the Knudsen number increases sufficiently; and the flow become rarefied. There is a reduction in the total heat flux rate as the sensor diameter is reduced.

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