scholarly journals Mesh independency study for an elementary perforated panel part of an air solar collector

2019 ◽  
Vol 85 ◽  
pp. 02017 ◽  
Author(s):  
Andrei-Stelian Bejan ◽  
Florin Bode ◽  
Tiberiu Catalina ◽  
Cătalin Teodosiu
Keyword(s):  
Numerical Model ◽  
Solar Collector ◽  
Metal Plate ◽  
Temperature Fields ◽  
Actual Case ◽  
Ansys Fluent ◽  
Numerical Grid ◽  
Computational Resources ◽  
Rng Turbulence Model ◽  
The Impact

In order to achieve the numerical model of a transpired solar collector (TSC) with integrated phase changing materials (PCM) it is mandatory to study the impact of the orifice geometry on the entire system. The numerical simulation of the entire solar collector absorber metal plate (1000x2000mm and 5000 orifices) is not feasible thus resulting a huge number of cells for the numerical grid for which we will need very high computational resources and a very large amount of time to be solved. By taking these aspects into account we decided to simulate only four equivalent orifices and then to transpose the results to the actual case for further studies. The present paper aims to analyse the mesh independency study for an elementary perforated panel with four equivalent lobed orifices which is part of a real case TSC. This analysis represents one of the most important stages within the construction of the TSC numerical model and doesn't need an experimental validation. The study was conducted in Ansys Fluent CFD software and the results were processed directly by using Tecplot software. Six different meshes were analysed (from 0.2 to 7.3 million cells), boundary conditions were imposed, and k-ε RNG turbulence model was used according to the literature. After comparing velocity and temperature fields in longitudinal and transverse planes we concluded that from 5.3 million cells the solution is independent of the meshing quality.

scholarly journals Numerical model of a solar ventilated facade element: experimental validation, final parameters and results

2019 ◽  
Vol 85 ◽  
pp. 02013 ◽  
Author(s):  
Andrei-Stelian Bejan ◽  
Florin Bode ◽  
Cătalin Teodosiu ◽  
Cristiana Verona Croitoru ◽  
Ilinca Năstase
Keyword(s):  
Numerical Simulation ◽  
Numerical Model ◽  
Solar Collector ◽  
Experimental Validation ◽  
Temperature Fields ◽  
Ansys Fluent ◽  
Flow Phenomena ◽  
Ventilated Facade ◽  
Real Flow ◽  
Computational Resources

The present paper analyses the airflow through the lobed orifices of a transpired solar collector which acts as a solar ventilated facade element through numerical simulation. This study is part of a complex research project which analyses the implementation of phase changing materials within air solar collectors. We decided to study an elementary part of the collectors' absorbent plate with four equivalent orifices in order to obtain the velocity and temperature field at the outlet of the computing domain since the numerical simulation of the entire solar collector (more than 5000 orifices) is not feasible due to the big amount of computational resources and time needed. This paper presents the experimental validation of the numerical model, its final parameters and preliminary results. The numerical simulation was conducted using Ansys Fluent CFD software and the results were processed via Tecplot. The boundary conditions imposed were emphasised and k-ε RNG turbulence model was used according to the literature. After comparing the velocity profiles and temperature fields obtained with both experimental and numerical approaches we concluded that the numerical model reproduces real flow phenomena within acceptable limits. The numerical model thus obtained will be used in further studies in order to optimise the collectors' geometry and characteristics by means of parametrical analyses.

scholarly journals Preliminary numerical studies conducted for the numerical model of a real transpired solar collector with integrated phase changing materials

2019 ◽  
Vol 111 ◽  
pp. 03047
Author(s):  
Andrei - Stelian Bejan ◽  
Cristiana Verona Croitoru ◽  
Florin Bode
Keyword(s):  
Global Warming ◽  
Numerical Model ◽  
Solar Collector ◽  
Cost Effective ◽  
Ansys Fluent ◽  
Numerical Studies ◽  
Building Systems ◽  
Feasible Option ◽  
Energy Consumptions ◽  
The Impact

Solar energy has a great potential to reduce the worldwide energy consumptions thus mitigating the impact of building systems on the global warming. Transpired solar collectors (TSC) are cost-effective solutions and phase changing materials (PCM) implemented within them could store the energy during the periods when solar radiation is available. The current paper is part of comprehensive numerical studies and analyses the mesh independency studies conducted in ANSYS Fluent with SST k-Ω viscous model and the numerical model preliminary results (3.3ºC rise in temperature). The results emphasise that the 5 million cells mesh is the feasible option for the studied case.

scholarly journals A Model for the Thermal Behaviour of an Offshore Cable Installed in a J-Tube

Proceedings ◽  
2020 ◽  
Vol 58 (1) ◽  
pp. 31
Author(s):  
Jeremy Arancio ◽  
Ahmed Ould El Moctar ◽  
Minh Nguyen Tuan ◽  
Faradj Tayat ◽  
Jean-Philippe Roques
Keyword(s):  
Sensitivity Analysis ◽  
Numerical Model ◽  
Thermal Behaviour ◽  
Energy Production ◽  
Power Transmission ◽  
Temperature Fields ◽  
Sobol Indices ◽  
Lumped Element ◽  
Thermal Phenomena ◽  
The Impact

In the race for energy production, supplier companies are concerned by the thermal rating of offshore cables installed in a J-tube, not covered by IEC 60287 standards, and are now looking for solutions to optimize this type of system. This paper presents a numerical model capable of calculating temperature fields of a power transmission cable installed in a J-tube, based on the lumped element method. This model is validated against the existing literature. A sensitivity analysis performed using Sobol indices is then presented in order to understand the impact of the different parameters involved in the heating of the cable. This analysis provides an understanding of the thermal phenomena in the J-tube and paves the way for potential technical and economic solutions to increase the ampacity of offshore cables installed in a J-tube.

Maximization of Solar Gains of an Air Collector by Simulations

2013 ◽  
Vol 284-287 ◽  
pp. 483-487 ◽  
Author(s):  
Ondrej Sikula ◽  
Vit Merka ◽  
Jiri Hirs ◽  
Josef Plášek
Keyword(s):  
Heat Transfer ◽  
Solar Energy ◽  
Solar Collector ◽  
Cfd Simulations ◽  
Ansys Fluent ◽  
Operation Conditions ◽  
Flow And Heat Transfer ◽  
Solar Air Collector ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact

The paper deals with numerical simulations of the impact of design, shading, positioning and orientation of a solar air collector an efficiency of exploitation of solar energy. The solar collector is used to preheat of an air, which then is supplied into the building. There are various requirements for solar air collectors. We are focused on maximization of solar energy gain by optimizing geometry, orientation and positioning of a solar air collector. To achieve the desired objective was a combination of two methods used. The firs one is Computational Fluid Dynamics (CFD) simulations of flow and heat transfer by convection, conduction and radiation in software ANSYS Fluent. The second one is the numerical simulation of the annual operations of the collector in the software BSim. The result of this work is an optimal design and operation conditions of the air collector.

Energy Efficiency Improvement of a Refrigerator Integrated With Phase Change Material-Based Condenser

2020 ◽  
Vol 143 (8) ◽  
Author(s):  
Devendra Dandotiya ◽  
Nitin D. Banker
Keyword(s):  
Numerical Model ◽  
Ambient Temperature ◽  
Phase Change ◽  
Phase Change Material ◽  
Coefficient Of Performance ◽  
Test Results ◽  
Ansys Fluent ◽  
Energy Efficiency Improvement ◽  
The Impact ◽  
Change Material

Abstract Energy consumption of a household refrigerator majorly depends on the ambient temperature and is highest at the noontime and lowest at the night. To mitigate the impact of higher ambient temperature, condenser of the refrigerator is modified by incorporating phase change material (PCM) in it. This article presents the development of numerical model of the PCM-based condenser and its comparison with the experimental model. A 3D numerical model for a PCM, namely, FS21-based condenser has been developed in commercial software ansys fluent 16.2, and the simulation outcomes are compared with the experimental test results. A correlation of a coefficient of performance (COP) which is a function of PCM temperature has been proposed. Based on the developed numerical model and the correlation, two other PCM-based heat exchangers, RT25 and RT25HC, are also analyzed numerically and their PCM temperatures are predicted. At the end, COP of the refrigerator with each PCM is compared.

Thermo-Solutal Convection of a Nanofluid Utilizing Fourier’s-Type Compass Conditions

2020 ◽  
Vol 9 (4) ◽  
pp. 362-374
Author(s):  
J. C. Umavathi ◽  
Ali J. Chamkha
Keyword(s):  
Brownian Motion ◽  
Prandtl Number ◽  
Boundary Conditions ◽  
Volume Fraction ◽  
Temperature Fields ◽  
Physical Parameters ◽  
Surface Boundary ◽  
Perturbation Scheme ◽  
Runge Kutta ◽  
The Impact

Nanotechnology has infiltrated into duct design in parallel with many other fields of mechanical, medical and energy engineering. Motivated by the excellent potential of nanofluids, a subset of materials engineered at the nanoscale, in the present work, a new mathematical model is developed for natural convection in a vertical duct containing nanofluid. Numerical scrutiny for the double-diffusive free and forced convection within a duct encumbered with nanofluid is performed. Buongiorno’s model is deployed to define the nanofluid. Robin boundary conditions are used to define the surface boundary conditions. Thermal and concentration equations envisage the viscous, Brownian motion, thermosphores of the nanofluid, Soret and Dufour effects. Using the Boussi-nesq approximation the solutal buoyancy effect as a result of gradients in concentration are incorporated. The conservation equations which are nonlinear are numerically estimated using fourth order Runge-Kutta methodology and analytically ratifying regular perturbation scheme. The mass, heat, nanoparticle concentration and species concentration fields on eight dimensionless physical parameters such as thermal and mass Grashof numbers, Brownian motion parameter, thermal parameter, Prandtl number, Eckert number, Schmidt parameter, and Soret parameter are calculated. The impact of these parameters are outlined pictorially. The velocity and temperature fields are boosted with the thermal Grashof number. The Soret and the Schemidt parameters reduces the nanoparticle volume fraction but it heightens the momentum, temperature and concentration. At the cold wall thermal and concentration Grashof numbers reduces the Nusselt values but they increase the Nusselt values at the hot wall. The reversal consequence was attained at the hot plate. The perturbation and Runge-Kutta solutions are equal in the nonappearance of Prandtl number. The (E. Zanchini, Int. J. Heat Mass Transfer 41, 3949 (1998)). results are restored for the regular fluid. The heat transfer rate is high for nanofluid when matched with regular fluid.

The Influence of Lubricant Supply Conditions and Bearing Configuration on the Performance of (Semi) Floating Ring Bearing Systems for Turbochargers

2017 ◽  
Author(s):  
Luis San Andrés ◽  
Feng Yu ◽  
Kostandin Gjika
Keyword(s):  
Heat Flow ◽  
Thermal Energy ◽  
Operating Conditions ◽  
Temperature Fields ◽  
Engine Oil ◽  
Large Temperature ◽  
Oil Viscosity ◽  
Supply Pressure ◽  
The Impact ◽  
Bearing System

Engine oil lubricated (semi) floating ring bearing (S)FRB systems in passenger vehicle turbochargers (TC) operate at temperatures well above ambient and must withstand large temperature gradients that can lead to severe thermo-mechanical induced stresses. Physical modeling of the thermal energy flow paths and an effective thermal management strategy are paramount to determine safe operating conditions ensuring the TC component mechanical integrity and the robustness of its bearing system. On occasion, the selection of one particular bearing parameter to improve a certain performance characteristic could be detrimental to other performance characteristics of a TC system. The paper details a thermohydrodynamic model to predict the hydrodynamic pressure and temperature fields and the distribution of thermal energy flows in the bearing system. The impact of the lubricant supply conditions (pressure and temperature), bearing film clearances, oil supply grooves on the ring ID surface are quantified. Lubricating a (S)FRB with either a low oil temperature or a high supply pressure increases (shear induced) heat flow. A lube high supply pressure or a large clearance allow for more flow through the inner film working towards drawing more heat flow from the hot journal, yet raises the shear drag power as the oil viscosity remains high. Nonetheless, the peak temperature of the inner film is not influenced much by the changes on the way the oil is supplied into the film as the thermal energy displaced from the hot shaft into the film is overwhelming. Adding axial grooves on the inner side of the (S)FRB improves its dynamic stability, albeit increasing the drawn oil flow as well as the drag power and heat flow from the shaft. The predictive model allows to identify a compromise between different parameters of groove designs thus enabling a bearing system with a low power consumption.

scholarly journals Continuous high-resolution midlatitude-belt simulations for July–August 2013 with WRF

2017 ◽  
Vol 10 (5) ◽  
pp. 2031-2055 ◽  
Author(s):  
Thomas Schwitalla ◽  
Hans-Stefan Bauer ◽  
Volker Wulfmeyer ◽  
Kirsten Warrach-Sagi
Keyword(s):  
High Resolution ◽  
Land Surface ◽  
Large Scale ◽  
Temperature Fields ◽  
Surface Model ◽  
Limited Area ◽  
Data Set ◽  
Latitude Belt ◽  
Simulated Precipitation ◽  
The Impact

Abstract. Increasing computational resources and the demands of impact modelers, stake holders, and society envision seasonal and climate simulations with the convection-permitting resolution. So far such a resolution is only achieved with a limited-area model whose results are impacted by zonal and meridional boundaries. Here, we present the setup of a latitude-belt domain that reduces disturbances originating from the western and eastern boundaries and therefore allows for studying the impact of model resolution and physical parameterization. The Weather Research and Forecasting (WRF) model coupled to the NOAH land–surface model was operated during July and August 2013 at two different horizontal resolutions, namely 0.03 (HIRES) and 0.12° (LOWRES). Both simulations were forced by the European Centre for Medium-Range Weather Forecasts (ECMWF) operational analysis data at the northern and southern domain boundaries, and the high-resolution Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) data at the sea surface.The simulations are compared to the operational ECMWF analysis for the representation of large-scale features. To analyze the simulated precipitation, the operational ECMWF forecast, the CPC MORPHing (CMORPH), and the ENSEMBLES gridded observation precipitation data set (E-OBS) were used as references.Analyzing pressure, geopotential height, wind, and temperature fields as well as precipitation revealed (1) a benefit from the higher resolution concerning the reduction of monthly biases, root mean square error, and an improved Pearson skill score, and (2) deficiencies in the physical parameterizations leading to notable biases in distinct regions like the polar Atlantic for the LOWRES simulation, the North Pacific, and Inner Mongolia for both resolutions.In summary, the application of a latitude belt on a convection-permitting resolution shows promising results that are beneficial for future seasonal forecasting.

Fractality of Simulated Fracture

2009 ◽  
Vol 409 ◽  
pp. 154-160 ◽  
Author(s):  
Petr Frantík ◽  
Zbyněk Keršner ◽  
Václav Veselý ◽  
Ladislav Řoutil
Keyword(s):  
Numerical Model ◽  
Elastic Plate ◽  
Model Simulation ◽  
Element Model ◽  
The Other ◽  
Particle Model ◽  
Discrete Element Model ◽  
Fractal Nature ◽  
Discrete Elements ◽  
The Impact

The paper is focussed on numerical simulations of the fracture of a quasi-brittle specimen due to its impact onto a fixed rigid elastic plate. The failure of the specimen after the impact is modelled in two ways based on the physical discretization of continuum: via physical discrete elements and pseudo-particles. Advantages and drawbacks of both used methods are discussed. The size distribution of the fragments of the broken specimen resulting from physical discrete element model simulation follows a power law, which indicates the ability of the numerical model to identify the fractal nature of the fracture. The pseudo-particle model, on the other side, can successfully predict the kinematics of the fragments of the specimen under impact failure.

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