scholarly journals Numerical Analysis of a Water-Cooled Condenser at Startup Conditions for Refrigeration Applications Supported with Experiments

2021 ◽  
Author(s):  
Carlos Acosta
Keyword(s):  
Fluid Dynamics ◽  
Global Market ◽  
Time Dependent ◽  
Steady Condition ◽  
Cfd Simulations ◽  
Ambient Temperatures ◽  
Industrial Sectors ◽  
Operational Costs ◽  
Oscillatory Phase ◽  
Experimental Values

Refrigeration for commercial purposes is one of the industrial sectors with the largest energy consumption in the global market. Therefore, research and development of more efficient components such as compressors, condensers, and refrigerants continue to render promising results in terms of GWP and operational costs. However, Due to the urgency typically found in industry to develop prototypes, finding scalable solutions can be challenging. Arguably, this is the case for condenser and evaporators that are designed and assembled under the assumption that refrigeration systems operate at steady condition, where in real circumstances such systems operate under transients based on ambient temperatures or unfavorable startup conditions. The aim of this study is to characterize the thermal and fluid dynamics behavior of refrigerant R404a in a water-cooled condenser at startup conditions. The boundary conditions to solve the CFD simulations are taken from experimental values and set as user defined functions in a commercial software. The results displayed the time dependent oscillatory phase-transition details of the refrigerant throughout the domain.

Unsteady 360 Computational Fluid Dynamics Validation of a Turbine Stage Mainstream/Disk Cavity Interaction

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
A. V. Mirzamoghadam ◽  
S. Kanjiyani ◽  
A. Riahi ◽  
Reddaiah Vishnumolakala ◽  
Lavan Gundeti
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Swirling Flows ◽  
Time Dependent ◽  
Cover Plate ◽  
Turbine Stage ◽  
Flow Conditions ◽  
Unstable Flow ◽  
Cfd Simulations ◽  
Purge Flow

The amount of cooling air assigned to seal high pressure turbine (HPT) rim cavities is critical for performance as well as component life. Insufficient air leads to excessive hot annulus gas ingestion and its penetration deep into the cavity compromising disk or cover plate life. Excessive purge air, on the other hand, adversely affects performance. Experiments on a rotating turbine stage rig which included a rotor–stator forward disk cavity were performed at Arizona State University (ASU). The turbine rig has 22 vanes and 28 blades, while the cavity is composed of a single-tooth lab seal and a rim platform overlap seal. Time-averaged static pressures were measured in the gas path and the cavity, while mainstream gas ingestion into the cavity was determined by measuring the concentration distribution of tracer gas (carbon dioxide) under a range of purge flows from 0.435% (Cw = 1540) to 1.74% (Cw = 6161). Additionally, particle image velocimetry (PIV) was used to measure fluid velocity inside the cavity between the lab seal and the rim seal. The data from the experiments were compared to time-dependent computational fluid dynamics (CFD) simulations using fluent CFD software. The CFD simulations brought to light the unsteadiness present in the flow during the experiment which the slower response data did not fully capture. An unsteady Reynolds averaged Navier–Stokes (RANS), 360-deg CFD model of the complete turbine stage was employed in order to increase the understanding of the swirl physics which dominate cavity flows and better predict rim seal ingestion. Although the rotor–stator cavity is geometrically axisymmetric, it was found that the interaction between swirling flows in the cavity and swirling flows in the gas path create nonperiodic/time-dependent unstable flow patterns which at the present are not accurately modeled by a 360 deg full stage unsteady analysis. At low purge flow conditions, the vortices that form inside the cavities are greatly influenced by mainstream ingestion. Conversely at high purge flow conditions the vortices are influenced by the purge flow, therefore ingestion is minimized. The paper also discusses details of meshing, convergence of time-dependent CFD simulations, and recommendations for future simulations in a rotor–stator disk cavity such as assessing the observed unsteadiness in the frequency domain in order to identify any critical frequencies driving the system.

scholarly journals Numerical investigation of the hydrocyclone vortex finder depth on separation efficiency

2021 ◽  
Vol 347 ◽  
pp. 00039
Author(s):  
Lesiba Mokonyama ◽  
Thokozani Justin Kunene ◽  
Lagouge Kwanda Tartibu
Keyword(s):  
Fluid Dynamics ◽  
Cfd Simulation ◽  
Fine Particles ◽  
Volume Fraction ◽  
Separation Efficiency ◽  
Cfd Simulations ◽  
Industrial Sectors ◽  
Air Core ◽  
Vortex Finder ◽  
Computational Fluid Dynamics Cfd

Hydrocyclones are devices used in numerous chemicals, food, and mineral-related industrial sectors for the separation of fine particles. A d50 mm hydrocyclone was modelled with the use of the Computational fluid dynamics (CFD) simulation, ANSYS® Fluent 2021 R1. The vortex finder depth was varied from 20 mm, 30 mm, and 35 mm to observe the effects of pressure drop and separation efficiency from a varied vortex finder depth and characteristics of the air core. The numerical methods validated the results observed from different parameters such as volume fraction characteristics based on CFD simulations. The tangential and axial velocities increased as the vortex finder length increased. It was found that as the depth of the vortex finder is increased, particle re-entrainment time in the underflow stream increases, and separation efficiency improved.

scholarly journals Effect of Bolts on Flow and Heat Transfer in a Rotor–Stator Disk Cavity

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Sulfickerali Noor Mohamed ◽  
John W. Chew ◽  
Nicholas J. Hills
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Time Dependent ◽  
Navier Stokes ◽  
Cfd Simulations ◽  
Flow And Heat Transfer ◽  
Gap Ratio ◽  
Computational Fluid Dynamics Cfd ◽  
Dependent Flow ◽  
Insight Into

Previous studies have indicated some differences between steady computational fluid dynamics (CFD) predictions of flow in a rotor–stator disk cavity with rotating bolts compared to measurements. Recently, time-dependent CFD simulations have revealed the unsteadiness present in the flow and have given improved agreement with measurements. In this paper, unsteady Reynolds averaged Navier–Stokes (URANS) 360 deg model CFD calculations of a rotor–stator cavity with rotor bolts were performed in order to better understand the flow and heat transfer within a disk cavity previously studied experimentally by other workers. It is shown that the rotating bolts generate unsteadiness due to wake shedding which creates time-dependent flow patterns within the cavity. At low throughflow conditions, the unsteady flow significantly increases the average disk temperature. A systematic parametric study is presented giving insight into the influence of number of bolts, mass flow rate, cavity gap ratio, and the bolts-to-shroud gap ratio on the time-dependent flow within the cavity.

Numerical and Experimental Study of Turbulent Flows Around Clark Y-14 Aerofoil

2015 ◽  
Author(s):  
Kshitij Vadake ◽  
Jie Cui
Keyword(s):  
Fluid Dynamics ◽  
Wind Tunnel ◽  
Real World ◽  
Force Measurement ◽  
Test Model ◽  
Wind Tunnel Testing ◽  
Cfd Simulations ◽  
Measurement Device ◽  
Tunnel Testing

Experimental Fluid Dynamics (EFD) and Computational Fluid Dynamics (CFD) have been instrumental in Fluid Mechanics to help solve scientific and engineering problems. This research attempts to use both techniques to perform a parametric study of turbulence flow around airfoil ClarkY-14 at various velocity and angle of attack (AoA). Clark Y-14 airfoil was designed in the 1920’s. It demonstrated good overall performance at low and moderate Reynolds numbers. With the progress in the aviation field, its performance was sub-optimal for newer aircraft designs. However, with the advent of RC airplanes and model aircrafts, there is a renewed interest in this airfoil. Various research projects have been conducted using this airfoil, but there hasn’t been a combined EFD and CFD study of the performance characteristics of the airfoil itself, which still finds real world applications today. One important aspect of this research included the investigation of the effects of a Force Measurement Device/Sensor, which is typically used in scaled/full-size wind tunnels to mount the test model as well as measure the forces/moments acting on it during the testing. The presence of such a device could affect the quality of the data obtained from the wind tunnel testing when compared to a real world application scenario where the aforementioned device may not be present. To the best of the author’s knowledge, no detailed study has been published on the effects of such devices. In this study, the results with and without the measuring device were generated by using CFD simulations. The results were then compared to see to what extent the inclusion of these devices will affect the results. The methodology used for this research was experimental as well as computational. In the present research, a commercially available CFD software STAR-CCM+ was employed to simulate the flows around airfoil Clark Y-14. The experimental data was obtained from wind tunnel tests using AEROLAB Educational Wind Tunnel (EWT) and compared with the simulation data from the CFD. The two data sets were in good agreement. Both experimental and simulation results were used to understand the effects of the measurement device/sensor used in the scaled wind tunnel on the lift and drag coefficients of the airfoil. Two separate CFD simulation setups were designed to model the presence and absence of the measurement device/sensor. These setups replicated the wind tunnel setup. The airfoil was tested and simulated at different speeds as well as different AoA. The comparative study gave a useful insight on the accuracy of the CFD simulations in relation to the actual testing. The analysis of results concluded that the force measurement device/sensor had insignificant effects on the accuracy and quality of data collected through wind tunnel testing.

scholarly journals Theoretical and experimental comparative studies of nonlinear optical properties for selected melaminium compounds

2010 ◽  
Vol 8 (6) ◽  
pp. 1192-1202 ◽  
Author(s):  
Marek Drozd ◽  
Mariusz Marchewka
Keyword(s):  
Optical Properties ◽  
Acetic Acid ◽  
Nonlinear Optical ◽  
Time Dependent ◽  
X Ray ◽  
Hartree Fock ◽  
Optical Applications ◽  
Experimental Values ◽  
Nonlinear Optical Applications ◽  
Theoretical Results

AbstractThe bis(melaminium) sulphate dihydrate, 2,4,6-triamine-1,3,5-triazin-1,3-ium tartrate monohydrate, 2,4,6-triamine-1,3,5-triazin-1-ium hydrogenphthalate, 2,4,6-triamine-1,3,5-triazin-1-ium acetate acetic acid solvate monohydrate, 2,4,6-triamine-1,3,5-triazin-1-ium bis(selenate) trihydrate, melaminium diperchlorate hydrate, melaminium bis(trichloroacetate) monohydrate and melaminium bis(4-hydroxybenzenesulphonate) dihydrate were discovered recently as perspective materials for nonlinear optical applications. On the basis of X-ray structures for eight melaminium compounds the time dependent Hartree Fock (TDHF) method was used for calculation of the polarizability, and first and second hyperpolarizability. Detailed directional studies of calculated hyperpolarizability for all investigated melaminium compounds are shown. The theoretical results are compared with experimental values of β.

scholarly journals Rapid pivot feeding in pipefish: flow effects on prey and evaluation of simple dynamic modelling via computational fluid dynamics

2008 ◽  
Vol 5 (28) ◽  
pp. 1291-1301 ◽  
Author(s):  
Sam Van Wassenbergh ◽  
Peter Aerts
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Analytical Model ◽  
Dynamic Modelling ◽  
Head Rotation ◽  
Theoretical Models ◽  
Cfd Simulations ◽  
Deceleration Phase ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Effects

Most theoretical models of unsteady aquatic movement in organisms assume that including steady-state drag force and added mass approximates the hydrodynamic force exerted on an organism's body. However, animals often perform explosively quick movements where high accelerations are realized in a few milliseconds and are followed closely by rapid decelerations. For such highly unsteady movements, the accuracy of this modelling approach may be limited. This type of movement can be found during pivot feeding in pipefish that abruptly rotate their head and snout towards prey. We used computational fluid dynamics (CFD) to validate a simple analytical model of cranial rotation in pipefish. CFD simulations also allowed us to assess prey displacement by head rotation. CFD showed that the analytical model accurately calculates the forces exerted on the pipefish. Although the initial phase of acceleration changes the flow patterns during the subsequent deceleration phase, the accuracy of the analytical model was not reduced during this deceleration phase. Our analysis also showed that prey are left approximately stationary despite the quickly approaching pipefish snout. This suggests that pivot-feeding fish need little or no suction to compensate for the effects of the flow induced by cranial rotation.

scholarly journals Effect of hydraulic and geometric factors upon leakage flow rate in pressurized pipes

RBRH ◽  
2021 ◽  
Vol 26 ◽  
Author(s):  
Mayara Francisca da Silva ◽  
Fábio Veríssimo Gonçalves ◽  
Johannes Gérson Janzen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Rate ◽  
Leakage Flow ◽  
Cfd Simulations ◽  
Mean Velocity ◽  
Leakage Flow Rate ◽  
Geometric Factors ◽  
Leakage Area ◽  
Computational Fluid Dynamics Cfd

ABSTRACT Computational Fluid Dynamics (CFD) simulations of a leakage in a pressurized pipe were undertaken to determine the empirical effects of hydraulic and geometric factors on the leakage flow rate. The results showed that pressure, leakage area and leakage form, influenced the leakage flow rate significantly, while pipe thickness and mean velocity did not influence the leakage flow rate. With relation to the interactions, the effect of pressure upon leakage flow rate depends on leakage area, being stronger for great leakage areas; the effects of leakage area and pressure on leakage flow rate is more pronounced for longitudinal leakages than for circular leakages. Finally, our results suggest that the equations that predict leakage flow rate in pressurized pipes may need a revision.

scholarly journals Computational Fluid Dynamics (CFD) as a tool for the analysis of ventilation and indoor microclimate in agricultural buildings

1997 ◽  
Vol 45 (1) ◽  
pp. 81-96 ◽  
Author(s):  
A. Mistriotis ◽  
T. De Jong ◽  
M.J.M. Wagemans ◽  
G.P.A. Bot
Keyword(s):  
Fluid Dynamics ◽  
Laboratory Experiments ◽  
Numerical Technique ◽  
Design Tool ◽  
Indoor Climate ◽  
Pressure Coefficients ◽  
Computational Fluid Dynamics Cfd ◽  
Basic Concepts ◽  
Experimental Values ◽  
Broiler House

The basic concepts of CFD are presented in relation to applications in modelling the ventilation process and the resulting indoor climate of agricultural buildings. The validity and the advantages of this numerical technique are presented using 3 examples. Firstly the pressure coefficients along the roof of a 7-span Venlo-type greenhouse were calculated and compared with the corresponding experimental values. Next, the ventilation process in a single-span greenhouse was investigated and the results were compared to laboratory experiments. Finally, the use of CFD as a design tool for more efficient ventilation systems was demonstrated for the case of a broiler house.

scholarly journals The Aerodynamics of a Diabolo

2021 ◽  
Author(s):  
Darren Jia
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Angular Momentum ◽  
Flow Pattern ◽  
High Spin ◽  
Angular Speed ◽  
Geometric Shape ◽  
Cfd Simulations ◽  
Resistive Torque ◽  
Computational Fluid Dynamics Cfd

Diabolo is a popular game in which the object can be spun at up to speeds of 5000 rpm. This high spin velocity gives the diabolo the necessary angular momentum to remain stable. The shape of the diabolo generates an interesting air flow pattern. The viscous air applies a resistive torque on the fast spinning diabolo. Through computational fluid dynamics (CFD) simulations it's shown that the resistive torque has an interesting dependence on the angular speed of the diabolo. Further, the geometric shape of the diabolo affects the dependence of torque on angular speed.

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