Experimental Study on the Flow Patterns and Two-phase Pressure Drops in a Horizontal Impacting T- Junction

The present paper analyzes the experimental results concerning the flow patterns and pressure drops in two-phase flow through an horizontal impacting T-junction, whose outlet pipes are aligned and perpendicular to the inlet pipe. The test section consists of plexiglass pipes with inner diameter of 10 mm. A mixture of water and air at ambient temperature and pressures up to 2.4 bar flows through the T-junction, with different splitting of flow rates in the two outlet branches; superficial velocities of air and water in the inlet pipe are varied up to a maximum of 35 m/s and 3.5 m/s respectively. The flow patterns occurring in the inlet and branch pipes were compared with the predictions of Baker’s and Taitel – Dukler’s maps. The pressure drops along the branches have been measured relatively to different splitting of the flow rate through the two branches and the pressure loss coefficients in the junction have been evaluated. Friction pressure drops have allowed us to evaluate two-phase friction multipliers, which have then been compared to the predictions of Lockhart-Martinelli, and Friedel correlations. Local pressure drops were extrapolated at the junction centre and analyzed; the two-phase multiplier has been evaluated and compared with the predictions of Chisholm correlation; the value of the empirical coefficient that minimizes the discrepancies has also been evaluated

Stereotaxic gamma knife surgery in treatment of critically located pilocytic astrocytoma: preliminary result

BACKGROUND: Low-grade gliomas are uncommon primary brain tumors, located more often in the posterior fossa, optic pathway, and brain stem and less commonly in the cerebral hemispheres. CASE PRESENTATIONS: Two patients with diagnosed recurrent cystic pilocytic astrocytoma critically located within the brain (thalamic and brain stem) were treated with gamma knife surgery. Gamma knife surgery (GKS) did improve the patient's clinical condition very much which remained stable later on. Progressive reduction on the magnetic resonance imaging (MRI) studies of the solid part of the tumor and almost disappearance of the cystic component was achieved within the follow-up period of 36 months in the first case with the (thalamic located lesion) and 22 months in the second case with the (brain stem located lesion). CONCLUSION: Gamma knife surgery represents an alternate tool in the treatment of recurrent and/or small postoperative residual pilocytic astrocytoma especially if they are critically locate

Two-phase flow in a horizontal t-junction : pressure drop and phase separation

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.An experimental investigation of dividing flow rates and pressure drops in a plexiglas tee junction with horizontal inlet, run, and branch sides using air-water mixtures has been performed. The branch stream is orthogonal to the inlet and run streams. The pipes forming the tee junction are about 1 m long, their inner diameter is 10 mm. The flow loop was supplied with compressed air and water through a mixing tee, at 1.5 bar and approximately ambient temperature. Air flow rate ranges from 0.3 to 9 Nl/s, water flow rate from 14.5 to 58 g/s, air superficial velocity from 1.5 to 47 m/s, water superficial velocity from 0.2 to 0.7 m/s and flow quality from 0.6% to 43%. The extraction ratio (branch flow rate / inlet flow rate) ranges from 0 to 1. Intermittent (bubble and slug flow) and annular flow patterns, as well as transition flow patterns have been obtained. Experimental values of flow rate, phases superficial velocity, extraction ratio and pressure drops across the tee junction pipes are here reported. Pressure drop test results across the inlet and branch pipes have also been compared with predicted ones. A new pressure drop correlation have been derived from test data.cs201

Two-phase flow in a horizontal t-junction : pressure drop and phase separation

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.An experimental investigation of dividing flow rates and pressure drops in a plexiglas tee junction with horizontal inlet, run, and branch sides using air-water mixtures has been performed. The branch stream is orthogonal to the inlet and run streams. The pipes forming the tee junction are about 1 m long, their inner diameter is 10 mm. The flow loop was supplied with compressed air and water through a mixing tee, at 1.5 bar and approximately ambient temperature. Air flow rate ranges from 0.3 to 9 Nl/s, water flow rate from 14.5 to 58 g/s, air superficial velocity from 1.5 to 47 m/s, water superficial velocity from 0.2 to 0.7 m/s and flow quality from 0.6% to 43%. The extraction ratio (branch flow rate / inlet flow rate) ranges from 0 to 1. Intermittent (bubble and slug flow) and annular flow patterns, as well as transition flow patterns have been obtained. Experimental values of flow rate, phases superficial velocity, extraction ratio and pressure drops across the tee junction pipes are here reported. Pressure drop test results across the inlet and branch pipes have also been compared with predicted ones. A new pressure drop correlation have been derived from test data.cs201

Gas Driven Circulation in an Adiabatic Air-Water Loop With Reference to Accelerator Driven Systems

In order to investigate the fluid dynamic mechanisms of the gas driven circulation, with reference to the accelerator driven systems (ADS), an experimental research with water driven by air injected at the inlet of the vertical riser in an adiabatic test rig has been carried out. The present experimental apparatus consists essentially of two vertical plexiglass pipes 3.8 m long, 0.08 m I.D., that are connected at the bottom by a horizontal pipe and at the top by a large open tank. The test rig is equipped with differential pressure transducers and two quick closing valves to measure the pressure drops and the average void fraction. The air flow rate ranges up to 5000 Nl/h, at 7 bar pressure, and the liquid flow rate can reach the value of more than 5 kg/s. The research aim is to investigate the effect of the superficial gas velocity on the superficial liquid velocity, on the void fraction and on the pressure drops, for a given geometry. The test data have been compared with some two-phase pressure drops and void fraction correlations. The geometry effect has been investigated too