Thermal Performance of the U-Tube Solar Collector Using Computational Fluid Dynamics Simulation

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Rim Farjallah ◽  
Monia Chaabane ◽  
Hatem Mhiri ◽  
Philippe Bournot ◽  
Hatem Dhaouadi
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Model ◽  
Flow Rate ◽  
Solar Collector ◽  
Numerical Study ◽  
Numerical Results ◽  
Dynamics Simulation ◽  
Working Fluid ◽  
Discrete Ordinates

In this paper, we propose a numerical study of a tubular solar collector with a U-tube. A three-dimensional numerical model is developed. It was first used in order to study the efficiency of the solar collector and to evaluate the validity of the developed computational fluid dynamics (CFD) model by comparison with experimental results from the literature. For the numerical simulations, the turbulence and the radiation were, respectively, modeled using the standard k–ε model and the discrete ordinates (DO) model. This numerical model was then used to carry out a parametrical study and to discuss the effect of selected operating parameters such as the fluid mass flow rate, the absorber selectivity, and the material properties. Numerical results show that with the increase of the working fluid flow rate from 0.001 kg/s to 0.003 kg/s, the efficiency of the solar collector is improved (from 30% to 35%). Numerical results also show that the filled-type evacuated tube with graphite presents a best result in comparison with those found using the copper fin tube (η increases from 54% to 64%). Finally, we noted that the use of a high selective absorber surface adds to better performance in comparison with the black absorber tube. This is mainly due to the radiation losses reduction.

Investigating the Cause of Computational Fluid Dynamics Deficiencies in Accurately Predicting the Efficiency and Performance of High Pressure Turbines: A Combined Experimental and Numerical Study

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Meinhard T. Schobeiri ◽  
S. Abdelfattah ◽  
H. Chibli
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Pressure ◽  
Numerical Study ◽  
Turbine Rotor ◽  
Sensitivity Study ◽  
Numerical Results ◽  
Performance Measurements ◽  
And Performance ◽  
The Individual

Despite the tremendous progress over the past three decades in the area of turbomachinery computational fluid dynamics, there are still substantial differences between the experimental and the numerical results pertaining to the individual flow quantities. These differences are integrally noticeable in terms of major discrepancies in aerodynamic losses, efficiency, and performance of the turbomachines. As a consequence, engine manufacturers are compelled to frequently calibrate their simulation package by performing a series of experiments before issuing efficiency and performance guaranty. This paper aims at identifying the quantities, whose simulation inaccuracies are preeminently responsible for the aforementioned differences. This task requires (a) a meticulous experimental investigation of all individual thermofluid quantities and their interactions, resulting in an integral behavior of the turbomachine in terms of efficiency and performance; (b) a detailed numerical investigation using appropriate grid densities based on simulation sensitivity; and (c) steady and transient simulations to ensure their impact on the final numerical results. To perform the above experimental and numerical tasks, a two-stage, high-pressure axial turbine rotor has been designed and inserted into the TPFL turbine research facility for generating benchmark data to compare with the numerical results. Detailed interstage radial and circumferential traversing presents a complete flow picture of the second stage. Performance measurements were carried out for design and off-design rotational speed. For comparison with numerical simulations, the turbine was numerically modeled using a commercial code. An extensive mesh sensitivity study was performed to achieve a grid-independent accuracy for both steady and transient analysis.

scholarly journals Lift Force of Airfoil (NACA 0012, NACA 4612, NACA 6612) With Variation of Angle of Attack and Camber: Computational Fluid Dynamics Study

2021 ◽  
Vol 4 (2) ◽  
pp. 80
Author(s):  
Mariza D. Ardany ◽  
Paken Pandiangan ◽  
Moh. Hasan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Rate ◽  
Lift Force ◽  
Angle Of Attack ◽  
Dynamics Simulation ◽  
Computational Fluid Dynamics Simulation ◽  
Internal Factors ◽  
Airfoil Flow ◽  
Naca 0012

Airfoil is a cross section from air plane wings can affect aerodynamic performance to lift force (FL). The lift force generated by airfoil has different values due to several external and internal factors, including angle of attack, flow rate and camber. To find the lift force of airfoils with different cambers and variations angle of attack and then flow rate can use computational fluid dynamics simulation. Computational fluid dynamics is simulation on a computer that can complete systems for fluid, heat transfer and other physical processes. This research using computational fluid dynamics simulation performed by SolidWorks, with NACA airfoil type which has different camber NACA 0012, NACA 4612 and NACA 6612. The angle of attack used in research was 0o, 4o, 8o, 12o, 16o and 20o. Flow rate used in research was 20m/s, 40 m/s, 60 m/s, 80 m/s and 100 m/s. From this research will be the bigger camber can produce a greater force lift. In addition, the greater airfoil flow rate can produce a greater force lift. This research also that the connection between force lift with coefficient lift (CL) is nonlinear quadratic form.

Experimental and Numerical Study of Cavitation in Centrifugal Pumps

2010 ◽  
Author(s):  
Erfan Niazi ◽  
M. J. Mahjoob ◽  
Ardeshir Bangian
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Mass Flow Rate ◽  
Computer Simulations ◽  
Mass Flow ◽  
Flow Rate ◽  
Numerical Study ◽  
Numerical Results ◽  
Centrifugal Pumps ◽  
Cavitation Threshold

Cavitation in pumps is one of the most important causes of damage to pumps impellers/inducers. A numerical model is developed here to simulate the pump hydraulics in different conditions. Experiments are also conducted to validate the computer simulations. To verify the numerical model, the h–m˙ (head versus mass flow rate) of the model is compared with the experimental data. The system is then run under cavitation state. Two methods are applied to monitor the cavitation threshold: first by using stroboscope and observing cavitation bubbles through the transparent casing of the pump and second by checking the NPSHA value for cavitation based on ISO3555. The paper then compares the experimental and numerical results to find the strengths and weaknesses of the numerical model.

scholarly journals Numerical study of flat plate solar collector performance with square shape wicked evaporator

2019 ◽  
Vol 12 (2) ◽  
pp. 90-97
Author(s):  
Basil Noori Merzah ◽  
Majid H. Majeed ◽  
Fouad A. Saleh
Keyword(s):  
Flat Plate ◽  
Heat Pipe ◽  
Flow Rate ◽  
Solar Collector ◽  
Numerical Study ◽  
Charge Ratio ◽  
Working Fluid ◽  
Evaporator Section ◽  
Fill Charge Ratio ◽  
Flat Plate Solar Collector

In this work, a system of a heat pipe is implemented to improve the performance of flat plate solar collector. The model is represented by square shape portion of the evaporator section of wicked heat pipe with a constant total length of 510 mm, and the evaporator section inclined by an angle of 30o. In this models the evaporator, adiabatic and condenser lengths are 140mm, 140mm, and 230mm respectively. The omitted energies from sunlight simulator are 200, 400, 600, 800 and 1000 W/m2 which is close to the normal solar energy in Iraq. The working fluid for all models is water with fill charge ratio of 240%. The efficiency of the solar collector is investigated with three values of condenser inlet water temperatures, namely (12, 16 and 20o C). The numerical result showed an optimum volume flow rate of cooling water in condenser at which the efficiency of collector is a maximum. This optimum agree well with the ASHRAE standard volume of flow rate for conventional tasting for flat plate solar collector. When the radiation incident increases the thermal resistance of wicked heat pipe is decreases, where the heat transfer from the evaporator to condenser increases. The numerical results showed the performance of solar collector with square shape evaporator greater than other types of evaporator as a ratio 15 %.

Computational Fluid Dynamics Simulation of Flow Mixing in Tunnel Kilns by Air Side Injection

2018 ◽  
Vol 10 (3) ◽  
Author(s):  
Adnan Ghareeb Tuaamah Al-Hasnawi ◽  
H. A. Refaey ◽  
T. Redemann ◽  
M. Attalla ◽  
E. Specht
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Rate ◽  
Cfd Simulation ◽  
Maximum Error ◽  
Dynamics Simulation ◽  
Maximum Temperature ◽  
Injection Velocity ◽  
Maximum Temperature Difference ◽  
Mixing Quality

The mixing of the two axial flows through the ware and through the gap between ware and walls using side nozzles in the preheating zone of tunnel kiln is investigated. The three-dimensional temperature field in the cross section between the two cars is calculated using the computational fluid dynamics (CFD) tool fluent. The mixing quality is evaluated using contours, the frequency of temperature distribution, and the maximum temperature difference. The influence on the mixing behavior of injection flow rate, injection velocity, nozzles position, and nozzle number has been analyzed. The results show that using two nozzles is more effective than one nozzle if the nozzles are installed at the opposite side walls with high vertical distance. The mixing quality increases strongly until an impulse flow rate (IFR) of about 4 N. For higher values, the influence becomes relatively low. The results for the mixing temperature obtained through CFD simulation compared with analytical results show a good agreement with maximum error of 0.5%.

scholarly journals Numerical Prediction of Microbubble Attachment in Biological Flows

2016 ◽  
Vol 13 (1) ◽  
Author(s):  
Joshua Gosney ◽  
Jeffrey Heys
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Model ◽  
Drag Force ◽  
Hydrodynamic Force ◽  
Fluid Velocity ◽  
Dynamics Simulation ◽  
Ultrasound Contrast ◽  
Biological Flows ◽  
Order Of Magnitude

Biofilm infections pose a major threat to human health and are difficult to detect. Microbubbles provide an effective and inexpensive method of detection for biofilm-based infections and other diseases such as cancer. The approach studied here examines the potential of targeted microbubbles, with specific antibodies covalently linked to their surfaces for use as ultrasound contrast agents and drug delivery vehicle. This work presents a novel numerical model for estimating the forces on microbubble conjugates in the vascular system. A full computational fluid dynamics simulation of biological fluid flow and the resulting forces on attached microbubbles is presented as well as comparisons with simplified analytical models. Both the computational and analytical predictions are compared with experimental measurements from Takalkar et al. and Schmidt et al., and these comparisons indicate stable microbubble attachment can be anticipated when the total hydrodynamic force on the microbubble is less than 100 pN. Through the examination of typical biological flows, microbubble attachment can be expected up to an average fluid velocity of 0.025 cm/s near the microbubble (i.e., a particle Reynolds number on the order of .001). The Stokes drag law was shown to predict the drag force (the dominant force) on the microbubble within an order of magnitude of the force predicted by the numerical model. Finally, it was found that the lift force on a microbubble was small relative to the drag force, and that the Saffman equation prediction differed from the numerical model by more than an order of magnitude for the biological flows examined. KEYWORDS: Microbubble Attachment; Ultrasound Contrast Agent; Hydrodynamic Force; Computational Fluid Dynamics

scholarly journals Advanced Computational Fluid Dynamics Study of the Dissolved Oxygen Concentration within a Thin-Layer Cascade Reactor for Microalgae Cultivation

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7284
Author(s):  
Karel Petera ◽  
Štěpán Papáček ◽  
Cristian Inostroza González ◽  
José María Fernández-Sevilla ◽  
Francisco Gabriel Acién Fernández
Keyword(s):  
Fluid Dynamics ◽  
Mass Transfer ◽  
Computational Fluid Dynamics ◽  
Dissolved Oxygen ◽  
Thin Layer ◽  
Oxygen Evolution ◽  
Numerical Study ◽  
Numerical Results ◽  
Oxygen Distribution ◽  
Microalgae Cultivation

High concentration of dissolved oxygen within microalgae cultures reduces the performance of corresponding microalgae cultivation system (MCS). The main aim of this study is to provide a reliable computational fluid dynamics (CFD)-based methodology enabling to simulate two relevant phenomena governing the distribution of dissolved oxygen within MCS: (i) mass transfer through the liquid–air interface and (ii) oxygen evolution due to microalgae photosynthesis including the inhibition by the same dissolved oxygen. On an open thin-layer cascade (TLC) reactor, a benchmark numerical study to assess the oxygen distribution was conducted. While the mass transfer phenomenon is embedded within CFD code ANSYS Fluent, the oxygen evolution rate has to be implemented via user-defined function (UDF). To validate our methodology, experimental data for dissolved oxygen distribution within the 80 meter long open thin-layer cascade reactor are compared against numerical results. Moreover, the consistency of numerical results with theoretical expectations has been shown on the newly derived differential equation describing the balance of dissolved oxygen along the longitudinal direction of TLC. We argue that employing our methodology, the dissolved oxygen distribution within any MCS can be reliably determined in silico, and eventually optimized or/and controlled.

scholarly journals Numerical Modelling and Experimental Validation of Twin-Screw Pumps Based on Computational Fluid Dynamics using SCORG® and SIMERICS MP+®

2021 ◽  
Vol 312 ◽  
pp. 05007
Author(s):  
Pasquale Borriello ◽  
Emma Frosina ◽  
Adolfo Senatore ◽  
Federico Monterosso
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Model ◽  
Pressure Distribution ◽  
Flow Rate ◽  
High Performance ◽  
Deep Understanding ◽  
Considerable Effect ◽  
Noise Emission ◽  
Computational Fluid Dynamics Analysis

This paper presents a methodology for simulating screw pumps using a 3D-CFD transient approach. It is known in literature that the advantages of screw pumps in noise emission, reliability, and their capacity to work with any kind of fluid make their applications interesting for many fields. Increasing demands for high-performance screw pumps require a deep understanding of the flow field inside the machine. The investigation is performed by use of a 3D computational fluid dynamics analysis based on a single-domain structured moving mesh obtained by novel grid generation procedure through the commercial software SCORG. The real-time mass flow rate, rotor torque, pressure distribution, velocity field, and other performance indicators including the indicated power were obtained from numerical simulations performed in the SimericsMP+ environment. The performance curves of the numerical model were produced for variable rotation speeds and discharge pressures and compared with experimental data with high accuracy. The pressure distribution in the screw groove is relatively uniform, the screw clearance and the meshing area pressure are different from the screw groove pressure distribution. The results demonstrate that the speed does not have a considerable effect on the pressure field. At last, the numerical model was validated by comparing the numerical results with the measured performance obtained in the experimental test rig through the comprehensive experiment performed for a set of discharge pressures and rotational speeds. The model has shown to predict pressure variation and flow rate with good accuracy.

Computational fluid dynamics simulation of the supersonic steam ejector. Part 2. Optimal design of geometry and the effect of operating conditions on the ejector

2011 ◽  
Vol 226 (3) ◽  
pp. 715-723 ◽  
Author(s):  
L Cai ◽  
H T Zheng ◽  
Y J Li ◽  
Z M Li
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Optimal Design ◽  
Critical Pressure ◽  
Operating Conditions ◽  
Dynamics Simulation ◽  
Working Fluid ◽  
Entrainment Ratio ◽  
Steam Ejector ◽  
Mixing Chamber

The aim of this study is to investigate the use of computational fluid dynamics in predicting the performance and optimal design of the geometry of a steam ejector used in a steam turbine. In the current part, the real gas model was considered using IAPWS IF97 model, and the influences of working fluid pressure and backpressure were investigated. The results illustrate that working critical pressure and backflow critical pressure exist in the flow. Moreover, the entrainment ratio reaches its peak at the working critical pressure. The performance of the ejector was nearly the same when the outlet pressure was lower than the critical backpressure. Effects of ejector geometries were also investigated. The distance between the primary nozzle and the mixing chamber was at optimum, the length of the mixing chamber and the diameter of the throat had an optimal value according to the entrainment ratio. When the length of the diffuser or throat was decreased within a range, the entrainment ratio did not change significantly.

Computational Fluid Dynamics Simulations of an Inertance Type Pulse Tube Refrigerator

2010 ◽  
Author(s):  
Dion Savio Antao ◽  
Bakhtier Farouk
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Heat Exchangers ◽  
Numerical Study ◽  
Working Fluid ◽  
Pulse Tube ◽  
Pulse Tube Refrigerator ◽  
Flow Recirculation ◽  
Temperature Heat

A numerical study is reported here for the investigation of the fundamental flow and heat transfer processes found in an inertance type pulse tube refrigerator (IPTR). The general design of an IPTR incorporates a pressure wave generator, a transfer line, an aftercooler, a regenerator, a pulse tube, a pair of heat exchangers for the cold and hot ends of the pulse tube, an inertance tube and a reservoir. The performance of the IPTR system is simulated using computational fluid dynamics (CFD) using cylindrical co-ordinates (r–z) and applying the axisymmetric assumption. The IPTR is driven by a cyclically moving piston at one end of the system operating at a fixed frequency with helium as the working fluid. Both constant temperature and convective heat transfer boundary conditions are examined along the external walls of the hot heat exchangers. The simulations reveal interesting steady-periodic flow patterns that develop in the pulse tube due to the fluctuations caused by the piston and the presence of the inertance tube. The secondary-flow recirculation patterns in the pulse tube reduce the heat pumping effect from the low-temperature heat exchanger to the high-temperature heat exchangers.

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