Pressure Mass Flow Rate Research Articles

CFD Simulation of Ejector in Steam Jet Refrigeration

In this study CFD technique was employed to investigate the effect of divergent angle of primary nozzle, NXP (NXP = Distance between the nozzle exit to mixing chamber inlet) and throat of the ejector on the performance of ejector using the steam jet refrigeration cycle. In all these cases, only one fixed mixing chamber with different divergent primary nozzle, NXP and throat of an ejector was investigated numerically using the commercial CFD package, the effect of primary fluid pressure mass flow rate and mach numbers were observed and analyzed. The velocity contour lines were used to explain the happening of process inside the ejector it was found that the throat diameter, NXP and diverging angle of primary nozzle plays a crucial role in the steam jet refrigeration.

Experimental investigation of a high aspect ratio, low speed contra-rotating fan stage with complex inflow distortion

This paper focuses on the response of a high aspect ratio, low speed contra-rotating fan with complex inflow distortion. The total pressure at the inlet is artificially distorted by means of two different sets of screens with different porosities to generate a hub-strong complex distortion and a tip-strong complex distortion. Detailed flow analyses were conducted for the design speed of rotor-1 in combination with off design speeds of rotor-2 both for the design and the peak pressure mass flow rates. In order to understand the extent of inlet distortion, the distortion sector was rotated circumferentially at intervals of 15° to cover the entire annulus. Detailed measurements of total pressure, static pressure, velocity components and flow angles were carried out at the inlet of the first rotor, between the two rotors and at the exit of the second rotor using three seven hole probes. The study reveals a few interesting aspects on the effect of complex inflow distortion on the flow behavior of a contra-rotating stage. The presence of a low porosity screen reduces the magnitude of axial velocity and generates higher spread of distortion near the localized region of placement of the screen. The hub-strong complex distortion has a greater effect of presence of this low porosity screen in both circumferential and radial directions. This leads to higher stagnation pressure variation at the inlet. On the other hand, for the tip-strong complex distortion case, the extent of distortion is observed to be higher in the circumferential direction towards the casing rather than radial. The localized improvement in the flow (in tip-strong inflow distortion) near the tip region improves the performance both in terms of pressure rise and efficiency of stage compared to hub–strong complex distortion.

A CFD model of two-phase flow in BWRs with results of sensitivity and uncertainty analysis

A Computational Fluid Dynamics model based on a two-fluid Eulerian description of the mass and momentum equations, two-equation mixture turbulence model and energy equation for the liquid phase is developed to predict the void distribution in a BWR assembly specified in the BFBT benchmark study. The effects of uncertainties in operating conditions, (pressure mass flow rate, inlet temperature, and power input) and model parameters, (momentum and heat exchange between the phases, heat transfer from the rods) has been analyzed. The results of both analysis indicate that the model predictions are more sensitive to experimental and modelling uncertainties in the low void fraction regions of the computational domain. The model predictions are in agreement with the experimental data with experimental and model uncertainties taken into account. Finally a sensitivity analysis of the model parameters has been performed and parameters of wall heat flux and heat transfer between the phases models have been identified as the major parameters that influence the phase distribution.