Preliminary design of a Knudsen pump
Creators: name: Μανιού, Αριστέα
Publisher: name: University of Thessaly
Year: 2011
Subjects: subject: ΑΝΤΛΙΕΣ ΘΕΡΜΟΤΗΤΟΣ
subject: ΡΕΥΣΤΟΜΗΧΑΝΙΚΗ

description: In this work, the phenomenon of thermal transpiration, also referred to as “thermal creep”, is studied. The Knudsen pump, is a type of vacuum pump that works by the principle of thermal transpiration. First of all, the dimensionless Knudsen number is defined, and the flow regimes, according to the different Knudsen numbers, are mentioned. A simple description of the phenomenon of thermal transpiration is provided. The purpose of this work is to investigate the basic flow configuration related to a preliminary design of a Knudsen pump, and for this we apply kinetic model equations to investigate the rarefied gas flow through a cylindrical tube whose ends are maintained at different temperatures. A detailed literature review of the phenomenon is provided along with details concerning the kinetic models developed to approximate the problem. The description of the problem and the formulation of the corresponding kinetic equations are presented, as well as the simulation of the boundary conditions. The problem is described by the integro - differentia] Boltzmann equation, which is used to determine the distribution of particles in physical and molecular velocity space, as well as in time. The macroscopic quantities of practical interest are obtained from the moments of the distribution function. In this work, the phenomenon of thermal transpiration, also referred to as “thermal creep”, is studied. The Knudsen pump, is a type of vacuum pump that works by the principle of thermal transpiration. First of all, the dimensionless Knudsen number is defined, and the flow regimes, according to the different Knudsen numbers, are mentioned. A simple description of the phenomenon of thermal transpiration is provided. The purpose of this work is to investigate the basic flow configuration related to a preliminary design of a Knudsen pump, and for this we apply kinetic model equations to investigate the rarefied gas flow through a cylindrical tube whose ends are maintained at different temperatures. A detailed literature review of the phenomenon is provided along with details concerning the kinetic models developed to approximate the problem. The description of the problem and the formulation of the corresponding kinetic equations are presented, as well as the simulation of the boundary conditions. The problem is described by the integro - differentia] Boltzmann equation, which is used to determine the distribution of particles in physical and molecular velocity space, as well as in time. The macroscopic quantities of practical interest are obtained from the moments of the distribution function.The kinetic model used in the simulations was the ellipsoidal model. In particular, we apply the non - linear ES model subject to Maxwell diffuse boundary conditions, to solve the non - isothermal flow of a rarefied gas through a cylindrical tube. The solutions provided, are valid in the whole range of the Knudsen number. Results regarding the flow, for the bulk quantities of velocity, heat flux, temperature and density are presented in terms of the three dimensionless parameters describing the flow, namely the rarefaction parameter δ, the temperature ratio TJT0Ut and the channel aspect ratio L/R. Finally, an overview of this work is presented together with some concluding remarks and some suggestions concerning future work in this field.