Modeling of the flow in thermo micropumps using a kinetic transport model. Ekapon Siwapornsathain

ISBN: 9780549634140

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154 pages


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Modeling of the flow in thermo micropumps using a kinetic transport model.  by  Ekapon Siwapornsathain

Modeling of the flow in thermo micropumps using a kinetic transport model. by Ekapon Siwapornsathain
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This dissertation describes how a simulation method using a kinetic model is used to compute the flow behavior of a rarefied gas inside micropumps. The method is called Convected Scheme (CS) which is a semi Lagrangian solution to the BoltzmannMoreThis dissertation describes how a simulation method using a kinetic model is used to compute the flow behavior of a rarefied gas inside micropumps. The method is called Convected Scheme (CS) which is a semi Lagrangian solution to the Boltzmann equation. The method is extended to include reflection off 90-degree interior corners, periodic boundaries and implementation of surfaces with various temperatures.

A new technique for setting the surface boundary condition will be introduced. Such a technique allows gas molecules to interact with a surface at any desired temperature. This involves a process of creating a table of particles phase-space distribution functions at temperatures of interest.

The technique was applied to the study of the thermal Fourier problem. Results showed that the effect of the mean-free path plays an important role in shaping the characteristics of the thermal profile of gas in the channel.-This work is extended further to study the flow inside the channel of two different micropumps whose operation is based on the thermal transpiration effect. The micropump of the first kind has ditches inside the channel to confine flow vortices and to allow multiple units of the same kind to be connected together.

After detailed studies of how the pumps geometry affects its performance, an optimized version of the device is proposed. The maximum flow speed achieved is nearly 25 m/s and the average molecular flow rate of 1.16 x 1026 molecules/m2-s at lambda of 2 mum. The micropump of the second kind has two sets of plates located next to each other.

During operation, one set is heated while the other remains unheated. This condition will create a thermal gradient in the spaces between the edges of the plates, and therefore drive the flow from unheated to heated plates.

A study was done to investigate how the geometrical parameters affect the flow rate. After optimization of the device, the maximum flow speed achieved is around 11 m/s and average molecular flow rate of 8.788 x 1025 molecules/m 2-s at Kn of 1.04.



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