This master thesis focused on optimizing the outlet geometry of microcolumn chips and how the chips are assembled in a miniaturized gas analysis system based on the principles of gas chromatography. The theory and literature of gas chromatography at microscales was studied and consequently several outlet designs were simulated with COMSOL Multiphysics®. Their theoretical velocity profiles were ...

• The actual flow rate is constant for the outlet pressure range of 35.30 psig to as low as a complete vacuum. The flow rate can be obtained from the charts on pages 16-18; e.g. for an orifice of .010" diameter and with 80 psig inlet pressure, the choked flow rate is 8.4 scfh (page 16). This flow rate will be constant for all outlet pressure conditions between 35.30 psig and full vacuum. 0 1 .5...

Deposition of sediment inside the conduit structures reduces the flow cross section area and increases the flow roughness which causes reduction of flow discharge passing through the conduit. Among the methods which can prevent sediment deposition is non sedimentation condition in the structure, Since the critical section of the inverted siphon in sedimentation is the outlet. In the begining of...

The management of mineral fertilization using centrifugal spreaders requires the development of spread pattern characterization devices to improve the quality of fertilizer spreading. In order to predict the spread pattern deposition using a ballistic flight model, several parameters need to be determined and especially the velocity of the granules when they leave the spinning disc. This paper ...

BACKGROUND Because of higher life expectancy, the number of elderly patients today with degenerative aortic diseases is on the increase. Often artificial aortic roots are needed to replace the native tissue. This surgical procedure requires re-implantation of the previous separated coronary arteries into the wall of the prosthesis. Regardless of the prosthesis type, changes in the reinsertion t...

The dynamics of Vestfonna ice cap (Svalbard) are dominated by fast-flowing outlet glaciers. Its mass balance is poorly known and affected dynamically by these fast-flowing outlet glaciers. Hence, it is a challenging target for ice flow modeling. Precise knowledge of the basal conditions and implementation of a good sliding law are crucial for the modeling of this ice cap. Here we use the full-S...

Background. Thoracic outlet syndrome may be due to various reasons and be classified as neurogenic, arterial, and venous thoracic outlet syndrome. The surgical treatment of neurogenic thoracic outlet syndrome can be performed using either a trans-axillary or a supraclavicular approach. The aim of this study is to report on such patients operated in a single institution by a single thoracic surg...

the fluid flow and heat transfer in a three-dimensional microchannel filled with al2o3- water nanofluid is numerically investigated. the hybrid scheme is used to discretize the convection terms and simpler algorithm is adopted to couple the velocity and pressure field in the momentum equations. the temperature fields, variation of horizontal velocity along the centre line of the channel, averag...

A three-dimensional computational fluid dynamics (CFD) model was used to calculate the velocity distribution among multiple parallel microchannels with triangle manifolds. The influences of structural parameters on velocity distribution among microchannels were analyzed. The simulation results showed that the velocity distribution became more uniform with larger microchannel length, depth or sm...

The severe vibration of a screw compressor outlet piping system caused the fatigue failure of some thermowells and the unscheduled shut down of the system. The main reasons of the abnormal vibration in the outlet piping system were investigated by developing an acoustic model to simulate the gas pulsation and establishing two finite element models to conduct the mechanical vibration analyses. T...