Prediction of Leak Rates Through Porous Gaskets at High Temperature

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Lotfi Grine ◽  
Abdel-Hakim Bouzid

The ability of a gasket to maintain tightness under different operating conditions has been studied extensively in recent years. However, most of the research studies conducted on leakage predictions was performed at room temperature. The aim of this work is to predict leakage through gaskets taking into account the effect of the temperature on the fluid properties and gasket internal structural characteristics. The analytical model of slip flow regime to evaluate the mass leak rates through a porous gasket developed by Grine and Bouzid (2011, “Correlation of Gaseous Mass Leak Rates Through Micro and Nano-Porous Gaskets,” ASME J. Pressure Vessel Technol.) was used in this study. The results from the model were validated and compared with the experimental data obtained from tests conducted on the Universal Gasket Rig with two different gases (helium and nitrogen). The leak rates measured are in the range of 1 to 0.0001 mg/s, which are measurable using the pressure rise technique. As a second objective, the influence of the gasket displacements caused by stress and temperature on the flow leakage was studied. A relationship between displacement or void thickness and leakage is clearly demonstrated. The slip flow regime model is capable of predicting leakage at temperature with reasonable accuracy.

Author(s):  
Lotfi Grine ◽  
Abdel-Hakim Bouzid

The ability of a gasket to maintain tightness under different operating conditions has been studied extensively in recent years. However most of the research studies conducted on leakage predictions was performed at room temperature. The aim of this work is to predict leakage through gaskets take into account the effect of the temperature on the fluid properties changes and gasket internal structural characteristics. The analytical model of slip flow regime to evaluate the mass leak rates through a porous gasket developed in [1] was used in this study. The results from the model were validated and compared with experimental data obtained from tests conducted on the Universal Gasket Rig with two different gases (Helium, Nitrogen). The leak rates measured are in the range of 1 to 10−4 mg/s, which is measurable using a pressure rise technique. As a second objective the influence of the gasket displacements caused by stress and temperature on the flow leakage was studied. A relationship between displacement or void thickness and leakage is clearly demonstrated. The slip flow regime model is capable of predicting leakage at temperature with reasonable accuracy.


Author(s):  
Vlasios Leontidis ◽  
Lucien Baldas ◽  
Stéphane Colin

Nowadays, modeling gas flows in the slip flow regime through microchannels can be achieved using commercial Computational Fluid Dynamics codes. In this regime the Navier-Stokes equations with appropriate boundary conditions are still valid. A simulation procedure has been developed for the modeling of thermal creep flow using ANSYS Fluent®. The implementation of the boundary conditions is achieved by developing User Defined Functions (UDFs) by means of C++ routines. The complete first order velocity slip boundary condition, including the thermal creep effects due to an axial temperature gradient and the effect of the wall curvature, and the temperature jump boundary condition are applied. Motivation of the present work is the development of a simulation tool which will help in the pre-calculations and the preliminary design of a Knudsen micropump consisting of successively connected curved and straight channels and in a second step in the numerical optimization of the pump, in terms of geometrical parameters and operating conditions of the system.


2016 ◽  
Vol 21 (2) ◽  
pp. 323-339
Author(s):  
P.K. Gaur ◽  
A.K. Jha ◽  
R. Sharma

Abstract A theoretical study is carried out to obtain an analytical solution of free convective heat transfer for the flow of a polar fluid through a porous medium with variable permeability bounded by a semi-infinite vertical plate in a slip flow regime. A uniform magnetic field acts perpendicular to the porous surface. The free stream velocity follows an exponentially decreasing small perturbation law. Using the approximate method the expressions for the velocity, microrotation, and temperature are obtained. Further, the results of the skin friction coefficient, the couple stress coefficient and the rate of heat transfer at the wall are presented with various values of fluid properties and flow conditions.


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