Modeling Strategy for the Analysis of Forced Draft Air-Cooled Condensers Using Rotational Fan Models

2019 ◽  
Vol 11 (5) ◽  
Author(s):  
Ruan A. Engelbrecht ◽  
Chris J. Meyer ◽  
Johan van der Spuy
Keyword(s):  
Numerical Models ◽  
Axial Flow ◽  
Numerical Results ◽  
Evaluation Tool ◽  
Complex Flow ◽  
Recovery Coefficient ◽  
Disk Model ◽  
Alternative Evaluation ◽  
Flow Phenomena ◽  
Modeling Strategy

Air-cooled condenser (ACC) design methodologies use empirical correlations that are unable to account for the complex flow phenomena associated with ACCs. Numerical models are seen as an alternative evaluation tool. This paper details the development of a modeling strategy for an ACC in the computational fluid dynamics (CFD) code of OpenFOAM. The axial flow fan is modeled using the extended actuator disk model (EADM) and validated using the B2a-fan. A good agreement between experimental and numerical results are noted for the volumetric flow rates expected in the ACC operating range. The A-frame heat exchanger is also validated using the empirical data. The ACC operating point is numerically and analytically determined. An overprediction of the numerical results to the analytical solution is attributed to the presence of kinetic energy recovery and validated using experimental results. A numerical recovery coefficient of 0.527 is measured and correlates well with the experimentally determined coefficient of 0.553.

scholarly journals Numerical Optimisation of The Diffuser In a Typical Turbocharger Compressor Using The Adjoint Method.

2021 ◽  
Author(s):  
Kristaq Hazizi ◽  
Ahad Ramezanpour ◽  
Aaron Costall
Keyword(s):  
High Efficiency ◽  
Numerical Models ◽  
A Priori ◽  
Central Area ◽  
Axial Flow ◽  
Operating Conditions ◽  
Complex Flow ◽  
Local Flow ◽  
Passenger Car ◽  
Partial Load

Abstract In the automotive industry, the demand for fuel economy and emission reduction has led to the downsizing of engines and turbochargers play a leading role in compensating for the performance loss. In complex flow modelling of the compressor, effective determination of the mesh resolution is not a priori due to variation of local flow and turbulence variables. In this study, the compressible flow of a centrifugal turbocharger compressor was numerically modelled. The accuracy of the models is discussed with respect to boundary layer adaptivity for the k-w SST turbulence model. The numerical models are investigated and verified against pick efficiency, extracted experimental points at 150,000 (rpm), along with other points of partial load at 80,000 (rpm) speed lines. The TD025-05T4 compressor of the 1.2 Litre engine Renault Megane passenger car was designed, constructed and provided experimental data (compressor map) by Mitsubishi Turbocharger and Engine Europe (MTEE). In addition, a numerical and mathematical study has been developed on the aerodynamic optimisation of the turbocharger compressor diffuser geometry. The optimisation of the single-target problem (efficiency) of the axial flow compressor outlet stage is carried out using a new smart evolutionary optimisation technique named adjoint solver. The Adjoint solver usually produces a surface vector field that shows how and where the geometry can be changed for optimisation based on a defined objective, efficiency in this study. Such irregular and non-parametric changes could be manufactured using recent advances in 3D printing technology.The expected result of optimisation of the diffuser geometry started with the design point, central area, 150,000 (rpm) speed line, shows a gradual development of efficiency to an uttermost of 2.5% and the process of optimisation has been enlarged and completed on all design operating areas selected previously. The development of an optimised geometry diffuser accomplishes a wider operating range, high efficiency and robust performance due to changes in engine operating conditions in the high-pressure area. Therefore, the optimal diffuser geometry leads to an impact on the engine’s efficiency and overall performance of a passenger car for real-world drive cycles, increasing power output and improving thermal efficiency.

Experimental/Numerical Crossover Jet Impingement in an Airfoil Leading-Edge Cooling Channel

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
K. Elebiary ◽  
M. E. Taslim
Keyword(s):  
Heat Transfer ◽  
Numerical Models ◽  
Computational Cost ◽  
Axial Flow ◽  
Leading Edge ◽  
Jet Impingement ◽  
Numerical Results ◽  
Proper Solution ◽  
Hexahedral Elements ◽  
Analytical Approaches

Technological advancement in the gas turbine field demands high temperature gases impacting on the turbine airfoils in order to increase the output power as well as thermal efficiency. The leading edge is one of the most critical and life limiting sections of the airfoil which requires intricate cooling schemes to maintain a robust design. In order to maintain coherence with a typical external aerodynamic blade profile, cooling processes usually take place in geometrically-complex internal paths where analytical approaches may not provide a proper solution. In this study, experimental and numerical models simulating the leading-edge and its adjacent cavity were created. Cooling flow entered the leading-edge cavity through the crossover ports on the partition wall between the two cavities and impinged on the internal surface of the leading edge. Three flow arrangements were tested: (1) and (2) being flow entering from one side (root or tip) of the adjacent cavity and emerging from either the same side or the opposite side of the leading-edge cavity, and (3) flow entering from one side of the adjacent cavity and emerging from both sides of the leading-edge cavity. These flow arrangements were tested for five crossover-hole settings with a focus on studying the heat transfer rate dependency on the axial flow produced by upstream crossover holes (spent air). Numerical results were obtained from a three-dimensional unstructured computational fluid dynamics model with 1.1 × 106 hexahedral elements. For turbulence modeling, the realizable k-ε was employed in combination with the enhanced wall treatment approach for the near wall regions. Other available RANS turbulence models with similar computational cost did not produce any results in better agreement with the measured data. Nusselt numbers on the nose area and the pressure/suction sides are reported for jet Reynolds numbers ranging from 8000 to 55,000 and a constant crossover hole to the leading-edge nose distance ratio, Z/Dh, of 2.81. Comparisons with experimental results were made in order to validate the employed turbulence model and the numerically-obtained results. Results show a significant dependency of Nusselt number on the axial flow introduced by upstream jets as it drastically diminishes the impingement effects on the leading-edge channel walls. Flow arrangement has immense effects on the heat transfer results. Discrepancies between the experimental and numerical results averaged between +0.3% and −24.5%; however, correlation between the two can be clearly observed.

scholarly journals Modeling a Large Air-Cooled Condenser

2021 ◽  
Vol 347 ◽  
pp. 00016
Author(s):  
D.L. Louw ◽  
C.J. Meyer ◽  
S.J. van der Spuy
Keyword(s):  
Characteristic Curve ◽  
Axial Flow ◽  
Leading Edge ◽  
Operating Conditions ◽  
Axial Flow Fan ◽  
Disk Model ◽  
Air Cooled Condensers ◽  
Shaft Power ◽  
Modeling Strategy ◽  
The Cost

This study reports on a modeling strategy for large Air-Cooled Condensers (ACCs). A large 64-fan ACC was modeled under various crosswind conditions that investigated the ACC’s specific axial flow fan configuration. The ACC model was developed in two parts, an axial flow fan model and a heat exchanger model. The axial flow fans were modeled using an Actuator Disk Model (ADM). The heat exchangers’ pressure drop was modeled using the Darcy-Forchheimer porosity model, and the Effectiveness Number of Transfer Units (ε-NTU) method was used to determine the air heat transfer rate. The ACC was configured using two different axial flow fans, identified in this study as the L-fan and the N-fan. Comparatively the L-fan has a steeper fan static pressure characteristic curve than that of the N-fan, at the cost of a greater shaft power consumption. Under normal operating conditions the average heat-to-power ratios were calculated at 89.91 W/W for the L-fan and 102.48 W/W for the N-fan. Under crosswind conditions of 9 m/s the heat-to-power ratios of the leading edge fan-units decreased by 80.6% and 87.0% for the L-fan and N-fan respectively. However, at the fan-units immediately downstream of the leading edge the heat-to-power ratios only decreased by 34.1% for the L-fan and 64.2% for the N-fan.

Experimental/Numerical Crossover Jet Impingement in an Airfoil Leading-Edge Cooling Channel

2011 ◽  
Author(s):  
K. Elebiary ◽  
M. E. Taslim
Keyword(s):  
Heat Transfer ◽  
Numerical Models ◽  
Computational Cost ◽  
Axial Flow ◽  
Leading Edge ◽  
Jet Impingement ◽  
Numerical Results ◽  
Proper Solution ◽  
Hexahedral Elements ◽  
Analytical Approaches

Technological advancement in gas turbine field demands high temperature gases impacting on the turbine airfoils in order to increase the output power as well as the thermal efficiency. Leading-edge is one of the most critical and life-limiting sections of the airfoil which requires intricate cooling schemes to maintain a robust design. In order to maintain coherence with a typical external aerodynamic blade profile, cooling processes usually take place in geometrically complex internal paths where analytical approaches may not provide a proper solution. In this study, experimental and numerical models simulating the leading-edge and its adjacent cavity were created. Cooling flow entered the leading-edge cavity through the crossover ports on the partition wall between the two cavities and impinged on the internal surface of the leading edge. Three flow arrangements were tested: 1,2) flow entering from one side (root or tip) of the adjacent cavity and emerging from either the same side or the opposite side of the leading-edge cavity and 3) flow entering from one side of the adjacent cavity and emerging from both sides of the leading-edge cavity. These flow arrangements were tested for five crossover-hole settings with a focus on studying the heat transfer rate dependency on the axial flow produced by upstream crossover holes (spent air). Numerical results were obtained from a three-dimensional unstructured computational fluid dynamics model with 1.1 million hexahedral elements. For turbulence modeling, the realizable k–ε was employed in combination with enhanced wall treatment approach for the near wall regions. Other available RANS turbulence models with similar computational cost did not produce any results in better agreement with the measured data. Nusselt numbers on the nose area and the pressure/suction sides are reported for jet Reynolds numbers ranging from 8000 to 55000 and a constant crossover hole to the leading-edge nose distance ratio, Z/Dh, of 2.81. Comparisons with experimental results were made in order to validate the employed turbulence model and the numerically-obtained results. Results show a significant dependency of Nusselt number on the axial flow introduced by upstream jets as it drastically diminishes the impingement effects on the leading-edge channel walls. Flow arrangement has immense effects on the heat transfer results. Discrepancies between the experimental and numerical results averaged between +0.3% and −24.5%, however correlation between the two can be clearly observed.

1203 Numerical analysis of complex flow phenomena in an axial flow turbine

2010 ◽  
Vol 2010 (0) ◽  
pp. 331-332
Author(s):  
Koichiro HARADA ◽  
Masato FURUKAWA ◽  
Kazutoyo YAMADA ◽  
Takanori SHIBATA
Keyword(s):  
Numerical Analysis ◽  
Axial Flow ◽  
Complex Flow ◽  
Flow Phenomena

Flow Phenomena in a Highly-Loaded Single-Stage Axial-Flow Pump: Comparison of Experimental and Numerical Results

2007 ◽  
Author(s):  
Friedrich-Karl Benra ◽  
Hans Josef Dohmen ◽  
Marina Schmidt
Keyword(s):  
Flow Structure ◽  
Flow Behavior ◽  
Axial Flow ◽  
Numerical Results ◽  
Operating Conditions ◽  
Flow Conditions ◽  
Part Load ◽  
Flow Phenomena ◽  
Operating Points ◽  
Highly Loaded

In highly loaded axial flow pumps considerable changes of the flow behavior were reported when altering the flow rate from design point operation to part load operation. The flow structure which is changing from stable operating conditions to stalled flow conditions has been investigated in detail by Kosyna and Stark with experimental methods. The present paper focuses on the application of numerical methods to simulate the flow behavior in the pump which has been investigated experimental. The obtained numerical results using a commercial solver for the unsteady Reynolds averaged Navier-Stokes equations (URANS) have been compared to the experimental results of Kosyna and Stark et al. The characteristic of the pump at different operating points is compared to the measurement. The change in the flow structure at part load conditions which gives a decrease of head is reproduced by the simulation results. The vortex structure induced by the tip leakage flow is a flow phenomenon which is well-known in external aerodynamics and in axial-flow compressors at flow conditions close to stall. The change of this vortex structure at different operating conditions is shown. Also the part load recirculation vortex dominating the rotor tip flow at deep stall conditions as well as the cross passage vortex is visualized from the numerical results. All addressed flow phenomena are shown in contrast to the findings of the experimental investigations. This comparison of the flow fields for appropriate operating points shows that the reported change in the flow structure can be detected by numerical simulation as well.

scholarly journals A New Experimental Study and SPH Comparison for the Sequential Dam-Break Problem

2020 ◽  
Vol 8 (11) ◽  
pp. 905
Author(s):  
Selahattin Kocaman ◽  
Kaan Dal
Keyword(s):  
Image Processing ◽  
Numerical Models ◽  
Flow Behavior ◽  
Rectangular Channel ◽  
Numerical Results ◽  
Dam Break ◽  
Frame Rate ◽  
Image Processing Technique ◽  
Complex Flow ◽  
The Impact

The floods following the event of a dam collapse can have a significant impact on the downstream environment and ecology. Due to the limited number of real-case data for dam-break floods, laboratory experiments and numerical models are used to understand the complex flow behavior and to analyze the impact of the dam-break wave for different scenarios. In this study, a newly designed experimental campaign was conducted for the sequential dam-break problem in a rectangular channel with a steep slope, and the obtained results were compared against those of a particle-based numerical model. The laboratory tests permitted a better understanding of the physical process, highlighting five successive stages observed in the downstream reservoirs: dam-break wave propagation, overtopping, reflection wave, run-up, and oscillations. Experimental data were acquired using a virtual wave probe based on an image processing technique. A professional camera and a smartphone camera were used to obtain the footage of the experiment to examine the effect of the resolution and frame rate on image processing. The numerical results were obtained through the Smoothed Particle Hydrodynamics (SPH) method using free DualSPHysics software. The experimental and numerical results were in good agreement generally. Hence, the presented data can be used as a benchmark in future studies to validate the SPH and other Computational Fluid Dynamics (CFD) methods.

Study of Available Turbulence and Cavitation Models to Reproduce Flow Patterns in Confined Flows

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
M. Coussirat ◽  
F. Moll ◽  
F. Cappa ◽  
A. Fontanals
Keyword(s):  
Numerical Models ◽  
Internal Flow ◽  
Numerical Results ◽  
Flow State ◽  
Quantitative Criterion ◽  
Complex Flow ◽  
Two Phase ◽  
Computational Costs ◽  
Extensive Analysis ◽  
Confined Flows

Cavitating flow in nozzles is a complex flow which implies a highly turbulent two-phase one. An accurate simulation which improves some numerical results found in the literature was achieved by means of an extensive analysis of the capabilities of several numerical models for turbulence and cavitation. The analysis performed involves calibration/optimization tasks based on the physics of this kind of flow. This work aims to provide a quantitative criterion for the judgment of internal flow state, because it was demonstrated that the numerical results obtained with noncalibrated models could be enhanced by means of a careful calibration and thus saving computational costs.

scholarly journals Numerical and experimental evaluation of masonry prisms by finite element method

2017 ◽  
Vol 10 (2) ◽  
pp. 477-508 ◽  
Author(s):  
C. F.R. SANTOS ◽  
R. C. S. S. ALVARENGA ◽  
J. C. L. RIBEIRO ◽  
L. O CASTRO ◽  
R. M. SILVA ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Finite Element Method ◽  
High Strength Concrete ◽  
Numerical Models ◽  
High Strength ◽  
Experimental Tests ◽  
Experimental Results ◽  
Concrete Blocks ◽  
Micro Modeling ◽  
Modeling Strategy

Abstract This work developed experimental tests and numerical models able to represent the mechanical behavior of prisms made of ordinary and high strength concrete blocks. Experimental tests of prisms were performed and a detailed micro-modeling strategy was adopted for numerical analysis. In this modeling technique, each material (block and mortar) was represented by its own mechanical properties. The validation of numerical models was based on experimental results. It was found that the obtained numerical values of compressive strength and modulus of elasticity differ by 5% from the experimentally observed values. Moreover, mechanisms responsible for the rupture of the prisms were evaluated and compared to the behaviors observed in the tests and those described in the literature. Through experimental results it is possible to conclude that the numerical models have been able to represent both the mechanical properties and the mechanisms responsible for failure.

Investigation of Mathematical Model of Turbulent Flow for Marine Propeller

2015 ◽  
Author(s):  
Nilima C. Joshi ◽  
Ayaz J. Khan
Keyword(s):  
Modern Technology ◽  
Hydrodynamic Performance ◽  
Marine Propeller ◽  
Turbulent Model ◽  
Complex Flow ◽  
Ansys Fluent ◽  
Flow Phenomena ◽  
Fluent Software ◽  
Effective Design ◽  
Mathematical And Numerical Modeling

ost of the flow phenomena important to modern technology involve turbulence. Propellers generally operate in the very complex flow field that may be highly turbulent and spatially non-uniform. Propeller skew is the single most effective design parameter which has significant influence on reducing propeller induced vibration. Up to date applications of propeller skew does not has a specified criteria for any turbulent model. This paper deals with the model which explains the effect of propeller skewness on hydrodynamic performance related to study of turbulent model via mathematical and numerical modeling. The simulation work is carried out using ANSYS-FLUENT software.

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