scholarly journals Influence of CFD Analysis on the Design of Cooling Channels for the CCL Cavity for the Spallation Neutron Source

2000 ◽  
Author(s):  
Snezana Konecni ◽  
Nathan K. Bultman
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Test Section ◽  
Cooling System ◽  
Flow Loop ◽  
Pressure Transducers ◽  
Cooling Channels ◽  
Recorded Data ◽  
Computational Fluid Dynamics Cfd ◽  
Turbine Flow Meter

Abstract Water flow in cooling channels was simulated using the computational fluid dynamics (CFD) code CFX4. Pressure drop in the cooling channels of the coupled-cavity linac (CCL) cavity was calculated. The effects of the manifold on the pressure drop were studied also. Reducing the pressure drop was a primary goal of this exercise that led to changing the cooling channel entrance regions. Results of this analysis were used in sizing pumps required for the cooling system. For the validation of the simplified numerical model, an experiment was performed to measure the pressure drop in the cooling channels for variable flow rate, using a flow loop. Deionized water was circulated through the test section with a pump and its flow rate was monitored with a turbine flow meter. Pressure was monitored with pressure transducers at five locations including a differential pressure transducer across the test section, and water temperature was taken at the exit of the pump. Pressure drop across the inlet and outlet of the test section was measured and recorded for different flow rates. Flow rate was also monitored and stored simultaneously. From the recorded data, an empirical correlation was derived to describe the pressure drop, dp, as a function of flow rate through the four cooling channels.

A Numerical Analysis on the System Impedance in a Fan Cooling System

2003 ◽  
Author(s):  
Dong-Il Kim ◽  
Ki-So Bok ◽  
Han-Bae Lee
Keyword(s):  
Numerical Analysis ◽  
Pressure Drop ◽  
Flow Rate ◽  
Pressure Difference ◽  
Cooling System ◽  
Computational Time ◽  
Computational Domain ◽  
Impedance Curve ◽  
Fan Cooling ◽  
Large Investment

To seek the fan operating point on a cooling system with fans, it is very important to determine the system impedance curve and it has been usually examined with the fan tester based on ASHRAE standard and AMCA standard. This leads to a large investment in time and cost, because it could not be executed until the system is made actually. Therefore it is necessary to predict the system impedance curve through numerical analysis so that we could reduce the measurement time and effort. This paper presents how the system impedance curve (pressure drop curve) is computed by CFD in substitute for experiment. In reverse order to the experimental principle of the fan tester, pressure difference was adopted first as inlet and outlet boundary conditions of the system and then flow rate was calculated. After determining the system impedance curve, it was compared with experimental results. Also the computational domain of the system was investigated to minimize computational time.

Identification of Design Criteria for Converter Cooling System of Permanent Magnet Direct-Drive Wind Turbine Generator

2016 ◽  
Author(s):  
Gerardo L. Augusto ◽  
Alvin B. Culaba ◽  
Laurence A. Gan Lim
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Cooling System ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Design Criteria ◽  
Direct Drive ◽  
Turbine Generator ◽  
Wind Turbine Generator ◽  
System Volume

The design criteria of converter cooling system for a 2.5 MW permanent magnet direct-drive wind turbine generator were investigated. Two (2) distribution networks with pipe sizes of DN40 and DN50 were used as basis for fluid flow analysis. The theoretical system pressure drop and system volume flow rate of converter cooling system were calculated using the governing equations of mass conservation, pump performance curve and distribution network characteristics. The system of nonlinear equations was solved using multivariable Newton-Raphson method with the solution vector determined using LU decomposition method. Numerical results suggest that the DN50 pipe provides a pressure drop limit of less than 300 Pa/m in the converter cooling system better than the pressure drop obtained from a DN40 pipe. The system volume flow rate of DN50 pipe was found to be above the operating limit of heat exchanger requirement of 135.30 L/min which needs to dissipate heat with a minimum of 50 kW.

Hydrodynamics of Pulse-Stabilized Fluidization at Incipient Fluidization

1999 ◽  
Author(s):  
Subhadeep Gan ◽  
Donald E. Beasley
Keyword(s):  
Pressure Drop ◽  
Secondary Flow ◽  
Fluidized Bed ◽  
Flow Rate ◽  
Test Section ◽  
Video Recording ◽  
Small Displacement ◽  
Pulsation Frequency ◽  
Primary Flow ◽  
Oscillatory Component

Abstract A laboratory scale experimental facility which models a Pulsed Atmospheric Fluidized Bed Combustor (PAFBC) has been developed; this facility is designed to examine the effect of an opposing secondary flow having an oscillatory component on a bubbling fluidized bed. The secondary flow is oriented in a vertical direction. The secondary flow is introduced into the bubbling bed through a tailpipe that extends through the bed and ends just above the porous polyethylene distributor. A pulsed flow simulator that employs a small displacement of a relatively large piston with variable drive radius and speed provides the oscillatory component of the secondary flow. The fluidized bed test section has a cross-sectional flow area of 30.5 by 30.5 cm with a height of 53 cm. Heat exchanger surfaces are modeled by two symmetric horizontal cylinders housed in the test section. The following test parameters are controlled: the primary flow rate, the mean secondary flow rate, the pulsation frequency and the amplitude of the secondary flow. Pressure taps are located just above the distributor and in the freeboard region to measure overall bed pressure drop. The facility is operated with a range of particles from 345 μm to 715 μm and a range of superficial fluidization velocities corresponding to the bubble flow regime. Fluidization curves were generated for traditional fluidization, using the primary flow through the porous distributor, with both primary and a steady secondary flow, and with primary and a pulsed secondary flow. Significant departures from the linear Darcy flow curves in the fixed bed region were observed, and attributed to significant local fluidization. Time resolved measurements of the overall bed pressure drop clearly indicate phase-locking behavior of the overall bed pressure drop with imposed frequency. Bubbles formed in pulse-stabilized fluidization are significantly smaller than in traditional fluidization, as observed through video recording of the present bed.

scholarly journals Assessment of Different Pressure Drop-Flow Rate Equations in a Pressurized Porous Media Filter for Irrigation Systems

Water ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2179
Author(s):  
Jonathan Graciano-Uribe ◽  
Toni Pujol ◽  
Jaume Puig-Bargués ◽  
Miquel Duran-Ros ◽  
Gerard Arbat ◽  
...  
Keyword(s):  
Porous Media ◽  
Pressure Drop ◽  
Flow Rate ◽  
Cfd Simulation ◽  
Silica Sand ◽  
Rate Equations ◽  
Uncertainty Range ◽  
Head Losses ◽  
Computational Fluid Dynamics Cfd ◽  
Drop Flow

The small open area available at the slots of underdrains in pressurized granular bed filters for drip irrigation implies: (1) the existence of a region with non-uniform flow, and (2) local values of modified particle Reynolds number >500. These flow conditions may disagree with those accepted as valid for common pressure drop-flow rate correlations proposed for packed beds. Here, we carried out detailed computational fluid dynamics (CFD) simulations of a laboratory filter to analyze the results obtained with five different equations of head losses in porous media: (1) Ergun, (2) Darcy-Forchheimer, (3) Darcy, (4) Kozeny-Carman and (5) power function. Simulations were compared with experimental data at different superficial velocities obtained from previous studies. Results for two silica sand media indicated that all equations predicted total filter pressure drop values within the experimental uncertainty range when superficial velocities <38.3 m h−1. At higher flow rates, Ergun equation approximated the best to the observed results for silica sand media, being the expression recommended. A simple analytical model of the pressure drop along flow streamlines that matched CFD simulation results was developed.

Study of the Effect of Turbulence Promoters in Circular Cooling Channels

2009 ◽  
Author(s):  
N. Cristobal Uzarraga-Rodriguez ◽  
Armando Gallegos-Mun˜oz ◽  
J. Cuauhtemoc Rubio-Arana ◽  
Alfonso Campos-Amezcua ◽  
Mazur Zdzislaw
Keyword(s):  
Pressure Drop ◽  
Aspect Ratio ◽  
Cooling System ◽  
Circular Cross Section ◽  
The Body ◽  
Internal Cooling ◽  
Combustion Gases ◽  
Cooling Channels ◽  
Cooling Effects ◽  
Volume Method

A numerical analysis of a gas turbine first stage bucket with internal cooling (model MS7001E) is presented. The internal cooling system consists of 13 cylindrical channels with turbulent promoters (ribs), which are implemented in order to achieve temperature decrements inside the body blade. Three different geometrics (square, triangular and semi-circular cross-section) are studied. Each configuration is analyzed having full or half ribs. These are placed inside the cooling channels. The effects generated by the aspect ratio variation between rib pitch and rib height (P/e), for a constant aspect ratio given by ribs height and hydraulic diameter (e/Dh) are considered. The numerical simulation was developed using finite volume method, by means of commercial software based on computational fluid dynamics (CFD). Each one of the models generated for each study case was built in a 3D model, including the platform and airfoil of the blade. The models consider the effects generated by the hot combustion gases are flowing around the blade and the coolant flow is flowing inside the cooling channels. The study includes the solution of the conjugate heat transfer. The results show that the cooling channels with squared and triangular full-ribs present better cooling effects inside the body blade, reducing the temperature until 10°C at some point in the blade. However, these configurations produce a pressure drop from 3 to 4 times higher than cooling channels without ribs. The half ribs produce lesser temperature decrement, having smaller pressure drop. On other hand, the aspect ratio (P/e) has only effects on the pressure drop.

Hole-Cleaning Performance of Gasified Drilling Fluids in Horizontal Well Sections

SPE Journal ◽  
2012 ◽  
Vol 17 (03) ◽  
pp. 912-923 ◽  
Author(s):  
E.M.. M. Ozbayoglu ◽  
R.E.. E. Osgouei ◽  
A.M.. M. Ozbayoglu ◽  
E.. Yuksel
Keyword(s):  
Liquid Phase ◽  
Pressure Drop ◽  
Flow Rate ◽  
Gas Flow ◽  
Flow Loop ◽  
Cuttings Transport ◽  
Flow Rates ◽  
Hole Cleaning ◽  
Gas Phases ◽  
Frictional Pressure Drop

Summary This study aims to investigate the hole-cleaning process during the flow of a drilling fluid consisting of a gas and a liquid phase through a horizontal annulus. Experiments have been conducted using the Middle East Technical University (METU) multiphase flow loop under a wide range of air- and water-flow rates while introducing cuttings into the annulus for different amounts. Data have been collected for steady-state conditions (i.e., liquid, gas, and cuttings injection rates are stabilized). Collected data include flow rates of liquid and gas phases, frictional pressure drop inside the test section, local pressures at different locations in the flow loop, and high-speed digital images for identification of solid, liquid, and gas distribution inside the wellbore. Digital imageprocessing techniques are applied on the recorded images for volumetric phase distribution inside the test section, which are in dynamic condition. The effects of liquid and gas phases are investigated on cuttings-transport behavior under different flow conditions. Observations showed that the major contribution for carrying the cuttings along the wellbore is the liquid phase. However, as the gas-flow rate is increased, the flow area left for the liquid phase dramatically decreases, which leads to an increase in the local velocity of the liquid phase causing the cuttings to be dragged and moved, or a significant erosion on the cuttings bed. Therefore, increase in the flow rate of gas phase causes an improvement in the cuttings transport although the liquid-phase flow rate is kept constant. On the basis of the experimental observations, a mechanistic model that estimates the total cuttings concentration and frictional pressure loss inside the wellbore is introduced for gasified fluids flowing through a horizontal annulus. The model estimations are in good agreement with the measurements obtained from the experiments. By using the model, minimum liquid- and gas-flow rates can be identified for having an acceptable cuttings concentration inside the wellbore as well as a preferably low frictional pressure drop. Thus, the information obtained from this study is applicable to any underbalanced drilling operation conducted with gas/liquid mixtures, for optimization of flow rates for liquid and gas phases to transport the cuttings in the horizontal sections in an effective way with a reasonably low frictional pressure loss.

scholarly journals Contributions of Kinetic Energy and Viscous Dissipation to Airway Resistance in Pulmonary Inspiratory and Expiratory Airflows in Successive Symmetric Airway Models With Various Bifurcation Angles

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Sanghun Choi ◽  
Jiwoong Choi ◽  
Ching-Long Lin
Keyword(s):  
Pressure Drop ◽  
Kinetic Energy ◽  
Viscous Dissipation ◽  
Flow Rate ◽  
Airway Resistance ◽  
Energy Balance Equation ◽  
Strongly Correlated ◽  
Bifurcation Angle ◽  
Computational Fluid Dynamics Cfd ◽  
Bifurcation Structures

The aim of this study was to investigate and quantify contributions of kinetic energy and viscous dissipation to airway resistance during inspiration and expiration at various flow rates in airway models of different bifurcation angles. We employed symmetric airway models up to the 20th generation with the following five different bifurcation angles at a tracheal flow rate of 20 L/min: 15 deg, 25 deg, 35 deg, 45 deg, and 55 deg. Thus, a total of ten computational fluid dynamics (CFD) simulations for both inspiration and expiration were conducted. Furthermore, we performed additional four simulations with tracheal flow rate values of 10 and 40 L/min for a bifurcation angle of 35 deg to study the effect of flow rate on inspiration and expiration. Using an energy balance equation, we quantified contributions of the pressure drop associated with kinetic energy and viscous dissipation. Kinetic energy was found to be a key variable that explained the differences in airway resistance on inspiration and expiration. The total pressure drop and airway resistance were larger during expiration than inspiration, whereas wall shear stress and viscous dissipation were larger during inspiration than expiration. The dimensional analysis demonstrated that the coefficients of kinetic energy and viscous dissipation were strongly correlated with generation number. In addition, the viscous dissipation coefficient was significantly correlated with bifurcation angle and tracheal flow rate. We performed multiple linear regressions to determine the coefficients of kinetic energy and viscous dissipation, which could be utilized to better estimate the pressure drop in broader ranges of successive bifurcation structures.

Experimental Investigation of Wax Deposition at Different Deposit Locations Through a Detachable Flow Loop Apparatus

2014 ◽  
Author(s):  
Si Li ◽  
Qiyu Huang ◽  
Wenda Wang ◽  
Changhui Wang ◽  
Zhenjun Ding
Keyword(s):  
Temperature Interval ◽  
Flow Rate ◽  
Test Section ◽  
Measurement Techniques ◽  
Operating Conditions ◽  
Temperature Fields ◽  
Wax Deposition ◽  
Flow Loop ◽  
Deposit Thickness ◽  
Wax Content

Wax deposition has always been a focus in the research field of flow assurance. Operating conditions are among the predominant factors that control the deposition rate and the nature of the formed deposits. However, the disadvantages of the available wax thickness measurement techniques applied to laboratory flow loops limit deeper studies on this issue. In this work, the effects of operating conditions, including temperature interval and flow rate, on wax deposition at different deposit locations are experimentally studied using a detachable flow loop apparatus. With the detachable test section, it is achievable to obtain the thickness and the wax content profiles of the deposit as functions of axial location and time. The temperature fields in the test section under both temperature intervals are simulated with CFD software FLUENT to provide more information for the analysis of deposition process. As the results manifest, the low temperature interval tends to intensify deposition, relating to the inner temperature field and wax precipitated property of the oil. The larger flow rate leads to a growth in the deposit thickness under the laminar flow regime and brings about a distinct rise in the wax content of deposit at inlet. In addition, the increase in deposit thickness and wax content indicates the phenomenon of deposit aging, and the wax deposit layer is thinner but with higher wax content at the inlet, due to the strong flow scour.

scholarly journals Comparing Performance Metrics of Partial Aisle Containments in Hard Floor and Raised Floor Data Centers Using CFD

Energies ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1473 ◽  
Author(s):  
Emelie Wibron ◽  
Anna-Lena Ljung ◽  
T. Staffan Lundström
Keyword(s):  
Flow Rate ◽  
Data Centers ◽  
Performance Metrics ◽  
Cooling System ◽  
Operating Conditions ◽  
Cooling Systems ◽  
Hot Air ◽  
Ansys Cfx ◽  
Computational Fluid Dynamics Cfd ◽  
Hard Floor

In data centers, efficient cooling systems are required to both keep the energy consumption as low as possible and to fulfill the temperature requirements. The aim of this work is to numerically investigate the effects of using partial aisle containment between the server racks for hard and raised floor configurations. The computational fluid dynamics (CFD) software ANSYS CFX was used together with the Reynolds stress turbulence model to perform the simulations. Velocity measurements in a server room were used for validation. Boundary conditions and the load of each rack were also retrieved from the experimental facility, implying an uneven load between the racks. A combination of the performance metrics Rack Cooling Index (RCI), Return Temperature Index (RTI) and Capture Index (CI) were used to evaluate the performance of the cooling systems for two supply flow rates at a 100% and 50% of operating condition. Based on the combination of performance metrics, the airflow management was improved in the raised floor configurations. With the supply flow rate set to operating conditions, the RCI was 100% for both raised floor and hard floor setups. The top- or side-cover fully prevented recirculation for the raised floor configuration, while it reduced the recirculation for the hard floor configuration. However, the RTI was low, close to 40% in the hard floor case, indicating poor energy efficiency. With the supply flow rate decreasing with 50%, the RTI increased to above 80%. Recirculation of hot air was indicated for all the containments when the supply rate was 50%, but the values of RCI still indicated an acceptable performance of the cooling system.

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