Cooling Fan Model for Thermal Design of Compact Electronic Equipment: Improvement of Modeling Using PQ Curve

2009 ◽  
Author(s):  
Hajime Nakamura
Keyword(s):  
Flow Rate ◽  
Cfd Simulation ◽  
Axial Flow ◽  
Volumetric Flow Rate ◽  
Thermal Design ◽  
System Effect ◽  
Simple Method ◽  
Cooling Fans ◽  
The Difference ◽  
The Impact

In order to hasten the thermal design for forced convection electronic devices, cooling fans should be modeled to reduce a computational load. A fan-curve-model, which generates volumetric flow rate versus the characteristics pressure difference of a fan, is very simple and usually incorporated into commercial CFD codes. However, this model often results in an erroneous flow rate. In this work, both the experiments and the CFD simulation were performed around small axial-flow-fans of 30 and 40 mm in diameter. The measured PQ curve was applied to the fan model, and compared the result of the simulation to the experimental data. It was clarified that the major reason behind the disagreement was the difference in the pressure definition of the fan model from the PQ curve measured using a chamber. Based on this, a simple method was proposed to correct this definition. Also, the system effect, which is the impact of obstacles on the fan delivery curve, was investigated by setting a cylindrical obstacle at upstream or downstream proximity of the fan.

The Effect of Hub Configuration on the Performance of an Air-Cooled Steam Condenser Fan

2020 ◽  
Author(s):  
Z. Meiring ◽  
S. J. van der Spuy ◽  
C. J. Meyer
Keyword(s):  
Flow Rate ◽  
Static Pressure ◽  
Axial Flow ◽  
Pressure Rise ◽  
Volumetric Flow Rate ◽  
Superior Performance ◽  
Design Point ◽  
Static Efficiency ◽  
Air Cooled Condensers ◽  
The Impact

Abstract Axial flow fans used in air-cooled condensers are typically analysed with smooth rounded hubs as they offer superior performance when compared to other hub configurations. However, such a hub configuration is impractical and may increase the manufacturing and installation costs of air-cooled condensers. As such, it is desirable to use a simpler, yet effective, hub configuration in order to reduce the installation cost. This paper assesses the impact that a simpler hub configuration may have on the performance of an axial flow fan. This is done through a comparison of three hub configurations: a cylindrical hub with a flat nose, a cylindrical hub with a hemispherical nose, and a disk hub, installed on the B2a-fan. Computational fluid dynamics modelling, utilising OpenFOAM, is used to simulate each hub configuration. It is found that the impact on performance due to hub configuration is dependent on the volumetric flow rate through the fan. A thin disk hub exhibits superior performance at low flow rates, resulting in a 8.4% improvement in total-to-static pressure rise and a 5.7% point improvement in total-to-static efficiency. As volumetric flow rate increases, the effectiveness of the disk hub configuration reduces while the hemispherical and flat nosed cylindrical hub configurations result in similar performance metrics at the design point flow rate. At above design point flow rate, the flat nosed cylindrical hub configuration shows an improvement in performance over the hemispherical nose cylindrical hub configuration, with a 9.5% increase in total-to-static pressure rise and a 5.1% point improvement in total-to-static efficiency.

Evaluation of Design Characteristics for Animal Mortality Composting Systems

2021 ◽  
Vol 65 (1) ◽  
pp. 23-30
Author(s):  
Tiago Costa ◽  
Neslihan Akdeniz
Keyword(s):  
Moisture Content ◽  
Linear Relationship ◽  
Compressive Stress ◽  
Flow Rate ◽  
Volumetric Flow Rate ◽  
Airflow Rate ◽  
List Type ◽  
Design Characteristics ◽  
The Impact ◽  
Composting Systems

HighlightsDesign characteristics for animal mortality compost cover materials were tested.Compressive stress was applied to simulate the effects of the mortalities on cover materials.The highest permeability was measured for sawdust at 25% moisture content.A linear relationship was found between the volumetric flow rate and the power required to aerate the piles.Abstract. Composting is an aerobic process that relies on natural aeration to maintain proper oxygen levels. Air-filled porosity, mechanical strength, and permeability are among the essential parameters used to optimize the process. This study’s objective was to measure the physical parameters and airflow characteristics of three commonly used cover materials at four moisture levels, which could be used in designing actively aerated swine mortality composting systems. A laboratory-scale experiment was conducted to measure pressure drops across the cover materials as a function of the airflow rate and the material’s moisture content. Compressive stress was applied for 48 h to simulate the impact of swine mortalities on the cover materials. The power required to aerate each material was determined as a function of volumetric flow rate and moisture content. As expected, air-filled porosity and permeability decreased with increasing bulk density and moisture content. The highest average permeability values were measured at 25% moisture content and ranged from 66 × 10-4 to 70 × 10-4 mm2, from 161 × 10-4 to 209 × 10-4 mm2, and from 481 × 10-4 to 586 × 10-4 mm2 for woodchips, ground cornstalks, and sawdust, respectively. For the range of airflow rates tested in this study (0.0025 to 0.0050 m3 s-1 m-2), a linear relationship (R2 = 0.975) was found between the volumetric flow rate (m3 s-1) and the power required to aerate the compost pile (W per 100 kg of swine mortality). Keywords: Airflow, Darcy’s law, Livestock, Modeling, Permeability, Pressure drop.

CFD Simulation of Passive Containment Cooling System in Hot Leg SB-LOCA for 1000MW PWR

2017 ◽  
Author(s):  
Jingya Li ◽  
Xiaoying Zhang
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Cfd Simulation ◽  
Driving Forces ◽  
Cooling System ◽  
Large Mass ◽  
Internal Cooling ◽  
Vapor Injection ◽  
The Difference

The passive cooling system (PCCS) for reactor containment is a security system that can be used to cool the atmosphere and reduce pressure inside of containment in case of temperature and pressure increase caused by vapor injection, which requires no external power because it works only with natural forces. However, as the driving forces from natural physical phenomena are of low amplitude, uncertainties and instabilities in the physical process can cause failure of the system. This article aims to establish a CFD simulation model for the Passive Containment Cooling System of 1000MW PWR using Code_Saturne and FLUENT software. The comparison of 4 different models based respectively on mixture model, COPAIN test, Uchida correlation and Chilton-Colburn analogy which simulate the condensing effect and the improvement of source code are based on a 3D simulation of PCCS system. To simulate the thermal-hydraulic condition in the containment after LOCA accident caused by a double-ended main pipe rupture, a high temperature vapor with the given mass flow rate are supposed to be the source of energy and mass into containment. Meanwhile the surface of three condensing island applies the wall condensation model. The simulation results show similar transient process obtained with the 4 models, while the difference between the transient simulation and the steady-state analysis of three models is less than 3%. The large mass flow rate of water loss status inside the containment cause a high flow rate of vapor which could be uniformly mixed with air in a short time. For the self-condensing efficiency of 3 groups of PCCS system, the non-centrosymmetric injection position resulting that the condensing efficiency is slightly higher for the two heat exchanger groups nearby. During the first 2400s of simulation time, more than 75.69% of the vapor is condensed, indicating that for the occurrence of condensation at the wall mainly driven by natural convection, the effect of thermodynamic siphon could improve the flow of gas mixture inside the tubes when the velocity of mixture is not large enough, so that the vapor could smoothly enter the tube and reach the internal cooling surface then to be condensed. Besides, PCCS ensure the containment internal pressure maintained below 2 bar and the temperature maintained below 380K during 3600s.

Unsteady Pressure Characteristics in the Mainstream/Disc Cavity of a Turbine-Stage

2017 ◽  
Author(s):  
A. V. Mirzamoghadam ◽  
J. Balasubramanian ◽  
M. Michael ◽  
R. P. Roy
Keyword(s):  
Flow Rate ◽  
Static Pressure ◽  
Cfd Simulation ◽  
Air Flow ◽  
Fast Response ◽  
Pressure Measurements ◽  
Turbine Stage ◽  
Unsteady Pressure ◽  
Purge Flow ◽  
The Difference

The interaction between the mainstream and disc cavity purge flows in a turbine stage is an unsteady 360° phenomenon. Most of the current rotating rigs have used steady pressure transducers to measure the mainstream annulus pressure distributions as well as the pressure distribution in the disc cavity. Unsteady static pressure measurements in these regions using fast-response transducers have also been reported but to a much lesser degree, mainly at ASU, OSU, VKI, and ETH. To gain better insight into the prevailing unsteady flow phenomena, and to assess the difference between steady and time-averaged unsteady pressure data, new unsteady static pressure measurements were recently carried out at three locations in an ASU-Honeywell turbine stage, namely, in the main gas path on the outer shroud near vane trailing edge as well as on the vane platform lip, and on the stator surface rim seal. They are reported in this paper along with the comparative results of the corresponding URANS CFD simulation reported in an earlier publication. Experiments were carried out at five different purge air flow conditions for each of the two mainstream air flow rate and rotor speed combinations. The current unsteady measurements indicate that the rim cavity pressure frequency is governed by the blade passage frequency. The unsteadiness amplitude increases with purge flow in the main gas path, but decreases with increase in purge flow for the rim cavity where the sensitivity to change in purge flow is smaller at the lower mainstream flow rate. The difference in the ambient-corrected time-averaged static pressures between those evaluated from the current unsteady measurements and the previously published steady measurements are found to be within the measurement uncertainties.

CFD Simulation of Installation Angle for Axial Flow Fan of a Motor

2013 ◽  
Vol 274 ◽  
pp. 212-215
Author(s):  
Jia Dong Tang ◽  
Yi Ping Lu ◽  
Xue Mei Sun ◽  
Wan Quan Zhang
Keyword(s):  
Flow Rate ◽  
Cfd Simulation ◽  
Volume Flow Rate ◽  
Axial Flow ◽  
Volume Flow ◽  
Hydraulic Efficiency ◽  
Axial Flow Fan ◽  
Installation Angle ◽  
Calculation Results ◽  
Blade Model

To analyze the effect of the installation angle on the performance of axial flow fan, single blade model and whole model was established, steady flow in the axial flow fan of the 7500KW air-cooled motor was simulated by software FLUENT. Volume flow rate and hydraulic efficiency of the fan with different installation angle under specific outlet pressures were analyzed, the effect of different turbulence model on the numerical simulation results was discussed, and the effect of the single blade model, the whole model and lengthened flow passage model on the numerical calculation results was compared. The results show that the fan volume flow rate and hydraulic efficiency is higher with the installation angle of 30°, the results simulated by standard k-ε model are close to the results simulated by k-ω-SST model, calculation results of these three methods have a good agreement with each other, and the result coincides well with experimental measured values.

scholarly journals Assessing the degree of plug flow in oxidation flow reactors (OFRs): a study on a potential aerosol mass (PAM) reactor

2018 ◽  
Vol 11 (3) ◽  
pp. 1741-1756 ◽  
Author(s):  
Dhruv Mitroo ◽  
Yujian Sun ◽  
Daniel P. Combest ◽  
Purushottam Kumar ◽  
Brent J. Williams
Keyword(s):  
Flow Rate ◽  
Cfd Simulation ◽  
Plug Flow ◽  
Volumetric Flow Rate ◽  
Flow Patterns ◽  
Space Time ◽  
Flow Reactors ◽  
Tracer Testing ◽  
Aerosol Mass ◽  
In Series

Abstract. Oxidation flow reactors (OFRs) have been developed to achieve high degrees of oxidant exposures over relatively short space times (defined as the ratio of reactor volume to the volumetric flow rate). While, due to their increased use, attention has been paid to their ability to replicate realistic tropospheric reactions by modeling the chemistry inside the reactor, there is a desire to customize flow patterns. This work demonstrates the importance of decoupling tracer signal of the reactor from that of the tubing when experimentally obtaining these flow patterns. We modeled the residence time distributions (RTDs) inside the Washington University Potential Aerosol Mass (WU-PAM) reactor, an OFR, for a simple set of configurations by applying the tank-in-series (TIS) model, a one-parameter model, to a deconvolution algorithm. The value of the parameter, N, is close to unity for every case except one having the highest space time. Combined, the results suggest that volumetric flow rate affects mixing patterns more than use of our internals. We selected results from the simplest case, at 78 s space time with one inlet and one outlet, absent of baffles and spargers, and compared the experimental F curve to that of a computational fluid dynamics (CFD) simulation. The F curves, which represent the cumulative time spent in the reactor by flowing material, match reasonably well. We value that the use of a small aspect ratio reactor such as the WU-PAM reduces wall interactions; however sudden apertures introduce disturbances in the flow, and suggest applying the methodology of tracer testing described in this work to investigate RTDs in OFRs to observe the effect of modified inlets, outlets and use of internals prior to application (e.g., field deployment vs. laboratory study).

The Impact of the Vortex Design Method on the Stall Behavior of Axial Flow Fan and Compressor Rotors

2008 ◽  
Author(s):  
Ja´nos Vad ◽  
Csaba Horva´th
Keyword(s):  
Flow Rate ◽  
Design Method ◽  
Axial Flow ◽  
Suction Side ◽  
Laser Doppler Anemometer ◽  
Design Flow ◽  
Performance Measurements ◽  
Global Performance ◽  
The Impact ◽  
Flow Blockage

The paper presents comparative studies on low-speed isolated rotors of free vortex design and controlled vortex design (CVD), in order to survey the impact of the vortex design method on the stall behavior of axial flow turbomachinery. The studies are based on 3D laser Doppler anemometer studies and global performance measurements, supplemented with literature data. CVD bladings are characterized by radially outward flow on the suction side due to spanwise changing circulation, and increased near-tip solidity and/or loading. These features were found to increase the near-tip endwall flow blockage and loss at the design flow rate, and to hasten stall. On this basis, it has been concluded that CVD tends to be disadvantageous from the viewpoint of the stall behavior. It was confirmed that forward blade sweep is a remedial strategy for moderating the stall-hastening effects of CVD, while retaining the favorable features of CVD.

scholarly journals EXPERIMENTAL ASSESSMENT OF THE IMPACT OF ASYMPTOMATIC GAS EMBOLI ON THE VESSEL WALL

2013 ◽  
Vol 13 (04) ◽  
pp. 1350064
Author(s):  
LINXIA GU ◽  
ERIC L. CUTLER
Keyword(s):  
Shear Stress ◽  
Flow Rate ◽  
Vessel Wall ◽  
Gas Bubbles ◽  
Volumetric Flow Rate ◽  
Injection Rate ◽  
Vascular Flow ◽  
Cardiovascular Flow ◽  
Forced Air ◽  
The Impact

Quantitative evaluation of shear stress in the vessel wall due to the presence of asymptomatic gas emboli is lacking. The goal of this work was to assess the impact of chronic asymptomatic gas emboli on the risk of atherosclerosis through a custom-built cardiovascular flow simulator. Gas bubbles were created by forced air from a syringe pump. The influences of embolism injection rate, pulse rate, and time-averaged flow rate on the wall mean shear stress were investigated at resting and elevated heart rate conditions. The recorded pressure and volumetric flow rate from 24 experimental settings with four repetitions each were used to calculate the mean wall shear stress (MWSS). A directly inverse relationship between gas embolus rate and MWSS in the vessel, particularly at low vascular flow and diminished pulse rates was subsequently found. This study established a positive correlation between gas bubbles in the bloodstream and diminished MWSS, which implied a potential onset of atherosclerosis.

Experiments on Gas Ingestion Through Axial-Flow Turbine Rim Seals

2004 ◽  
Author(s):  
R. P. Roy ◽  
J. Feng ◽  
D. Narzary ◽  
P. Saurabh ◽  
R. E. Paolillo
Keyword(s):  
Flow Rate ◽  
Cfd Simulation ◽  
Air Flow ◽  
Three Dimensional ◽  
Axial Flow ◽  
Air Flow Rate ◽  
Three Dimensional Flow ◽  
Turning Angle ◽  
Time Average ◽  
The Many

It has been suggested by researchers that ingestion, through rim seals, of mainstream gas into axial-flow turbine disk cavities is a consequence of the prevailing unsteady three-dimensional flow field. The cause-effect relationship is complex — to help understand it, experiments were performed in a model single-stage turbine rig using two different vane-blade configurations. Selected measurements from one of the configurations were reported earlier (1999–2001). The second configuration is new, featuring smaller numbers of vanes and blades and a larger vane turning angle. Selected measurements are presented and compared to those from the first configuration. The measurements include: unsteady and time-average static pressure spatial distributions, and spatial distribution, in the rotor-stator cavity, of time-average ingestion. The parameters in the experiments were: main air flow rate, purge/seal air flow rate, and rotor speed. Unsteady three-dimensional CFD simulation may be helpful in identifying the roles of the many intertwined phenomena in the ingestion process.

scholarly journals Numerical and experimental study of flow distribution in tubular space of fin-and-tube heat exchanger with modified inlet manifold

2018 ◽  
Vol 240 ◽  
pp. 02010
Author(s):  
Tomasz Stelmach
Keyword(s):  
Heat Exchanger ◽  
Flow Rate ◽  
Cfd Simulation ◽  
Tube Bundle ◽  
Cross Flow ◽  
Flow Distribution ◽  
Volumetric Flow Rate ◽  
Tube Heat Exchanger ◽  
Experimental Stand ◽  
Inlet Manifold

This paper presents the experimental and numerical investigation of flow distribution in the tubular space of cross-flow fin-and-tube heat exchanger. The tube bundle with two rows arranged in staggered formation is considered. A modified heat exchanged manifold, with inlet nozzle pipe located asymmetrically is considered. The outlet nozzle pipe is located in the middle of the outlet manifold, with a standard shape. An experimental stand allows one to investigate the volumetric flow rate in heat exchanger tubular space using the ultrasonic flowmeters. Various inlet mass flow rate i.e. 3 m3/h, 4 m3/h and 5 m3/h are considered. The experimental results are compared with CFD simulation performed in ANSYS CFX program using the SSG Reynolds Stress turbulence model. A relatively good agreement is found for tube Re numbers varied from 1800 to 3100.

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