Unsteady Flow Pattern Characteristics Downstream of a Forward-Curved Blades Centrifugal Fan

2000 ◽  
Vol 123 (2) ◽  
pp. 265-270 ◽  
Author(s):  
Sandra Velarde-Sua´rez ◽  
Rafael Ballesteros-Tajadura ◽  
Carlos Santolaria-Morros ◽  
Jose´ Gonza´lez-Pe´rez
Keyword(s):  
Operating Conditions ◽  
The Other ◽  
Low Flow ◽  
Centrifugal Fan ◽  
Hot Wire ◽  
Measured Velocity ◽  
Flow Rates ◽  
Velocity Fluctuations ◽  
Flow Asymmetry ◽  
Steady Velocity

The results of an experimental investigation of the flow at two exit radial locations of a forward-curved blades centrifugal fan are presented. Hot wire techniques were used to obtain steady velocity components and velocity unsteadiness levels (rms value of the components of velocity fluctuation) for different operating conditions. Globally speaking, the data reveal a strong flow asymmetry, with considerable changes in both magnitude and direction along the different circumferential positions. Particularly, big differences appear between the circumferential positions closer to the volute tongue and the other ones. The periodic character of the velocity signals due to the passing of the blades, clearly observed around the impeller, is missed in the vicinity of the volute tongue, where the main contribution to the velocity fluctuations appears to be random. Based on the measured velocity signals, velocity unsteadiness of the flow is determined analyzing the main contributions as a function of the flow rate and the measurement position. High levels of velocity unsteadiness were observed near the volute tongue, mainly at low flow rates.

Direct metabolic effects of isoproterenol and propranolol in ischemic myocardium of the dog

1980 ◽  
Vol 239 (4) ◽  
pp. H469-H469
Author(s):  
Michael Goodlett ◽  
Kyran Dowling ◽  
Lynne J. Eddy ◽  
James M. Downey
Keyword(s):  
High Energy ◽  
Ischemic Myocardium ◽  
The Other ◽  
Energy Utilization ◽  
Metabolic Effects ◽  
Low Flow ◽  
High Energy Phosphate ◽  
Drug Induced ◽  
Flow Rates ◽  
Induced Changes

The effect of either isoproterenol or propranolol on the metabolism of ischemic myocardium was examined. To ensure that all changes were due to changes in metabolism and not drug-induced changes in residual flow to the ischemic regions, we devised a preparation in which two coronary branches on the same heart were simultaneously perfused at a low flow rate. Microsphere measurements verified that the two ischemic regions were receiving identical blood flow rates. One branch received an infusion of 0.9% NaCl and the other received the drug. After 1 h both regions were biopsied and the high-energy phosphate levels in each region were determined. ATP and phosphocreatine each fell to about 50% of their starting values in the 0.9% NaCl-treated regions, and isoproterenol did not further depress the high-energy phosphate concentrations. Propranolol, on the other hand, significantly preserved the high-energy phosphate concentrations. We conclude that although isoproterenol seemed incapable of accelerating energy utilization in ischemic myocardium, propranolol is apparently capable of reducing it.

scholarly journals Effects of Operating Conditions on the Flow in the Moving Blade Passage of a Single Stage Axial-Flow Fan

1997 ◽  
Vol 3 (4) ◽  
pp. 269-276 ◽  
Author(s):  
Tsutomu Adachi ◽  
Yutaka Yamashita ◽  
Kennichiro Yasuhara ◽  
Tatsuo Kawai
Keyword(s):  
Three Dimensional ◽  
Axial Flow ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Hot Wire ◽  
Axial Flow Fan ◽  
Blade Passage ◽  
Operational Conditions ◽  
Flow Phenomena ◽  
Steady Velocity

Three dimensional steady and unsteady velocity distributions in the axial flow fan were measured using a hot wire probe for various operational conditions, various rotational speeds and various measuring positions. For measuring the velocity distributions in the blade passage, a specially designed and manufactured hot wire traversing apparatus was used. Steady velocity distributions, turning angles, effects of incident to the cascade, flow leakage through the tip clearance and effects of the flow separation show the flow phenomena through the blade passages. Unsteady velocity distributions show time dependent procedures of the wake flowing through the moving blade passage. Considering these results of measurements, the effects of the upstream stationary blade and the effects of Reynolds number on the flow were considered.

scholarly journals Investigation of the Flow Field in the Vicinity of an Axial Flow Fan During Low Flow Rates

2014 ◽  
Author(s):  
Francois G. Louw ◽  
Theodor W. von Backström ◽  
Sybrand J. van der Spuy
Keyword(s):  
Flow Field ◽  
Numerical Simulations ◽  
Flow Rate ◽  
Axial Flow ◽  
Operating Conditions ◽  
Design Flow ◽  
Low Flow ◽  
Axial Flow Fan ◽  
Free Vortex ◽  
Flow Rates

Large axial flow fans are used in forced draft air cooled heat exchangers (ACHEs). Previous studies have shown that adverse operating conditions cause certain sectors of the fan, or the fan as a whole to operate at very low flow rates, thereby reducing the cooling effectiveness of the ACHE. The present study is directed towards the experimental and numerical analyses of the flow in the vicinity of an axial flow fan during low flow rates. This is done to obtain the global flow structure up and downstream of the fan. A near-free-vortex fan, designed for specific application in ACHEs, is used for the investigation. Experimental fan testing was conducted in a British Standard 848, type A fan test facility, to obtain the fan characteristic. Both steady-state and time-dependent numerical simulations were performed, depending on the operating condition of the fan, using the Realizable k-ε turbulence model. Good agreement is found between the numerically and experimentally obtained fan characteristic data. Using data from the numerical simulations, the time and circumferentially averaged flow field is presented. At the design flow rate the downstream fan jet mainly moves in the axial and tangential direction, as expected for a free-vortex design criteria, with a small amount of radial flow that can be observed. As the flow rate through the fan is decreased, it is evident that the down-stream fan jet gradually shifts more diagonally outwards, and the region where reverse flow occur between the fan jet and the fan rotational axis increases. At very low flow rates the flow close to the tip reverses through the fan, producing a small recirculation zone as well as swirl at certain locations upstream of the fan.

Transport Phenomena in Novel Microstructures for Use in Thermal Separation Processes

2009 ◽  
Author(s):  
Lukas E. Wiesegger ◽  
Ralf P. Knauss ◽  
Thomas Winkler ◽  
Stefan Maikowske ◽  
Ju¨rgen J. Brandner ◽  
...  
Keyword(s):  
Gaseous Phase ◽  
Phase Distribution ◽  
Flow Direction ◽  
Test System ◽  
Operating Conditions ◽  
Low Flow ◽  
Optimum Operating ◽  
Liquid Distribution ◽  
Flow Rates ◽  
Vof Model

In the present work novel microstructures are developed and studied by means of analytical and numerical methods. These microstructures form part of a demonstration microdevice to carry out a distillation without chemical reaction, two for the liquid and gaseous phase distribution/collection, and one for the liquid/gas mass transfer (“μTU-I,-II”). A solution for the 3D velocity field for the velocity component w in flow direction can be given for the rectangular and semicircular microchannel by using a lubrication approximation which gives good realistic values for the Reynolds number at low flow rates comparing to the common 2D approaches. The μTU-I is studied using the CFD code (6.3 FLUENT ® - 3ddp) by the approach of the VOF model. The simulations are performed with the test system methanol/water (distillation). By varying the flow rates of both phases and the contact angle, the condition until the occurrence of flooding of the microunit “μTU-I” is determined. The flooding and the optimum operating conditions of a new optimized configuration “μTU-II” -microunit are also investigated by means of numerical simulation (CFD). It can be shown that longitudinal instability is generated. Based on several concepts for liquid and gaseous phase distribution/collection by the Forschungszentrum Karlsruhe, novel microstructures (“Liquid-Distribution-Collection-Microstructure”, “Vapor-Distribution-Collection-Microstructure”) for both phases are developed, studied and optimized by using CFD. The results of all studies are verified based on the demonstration device in the laboratory.

Forty-Seven–Well Case Study: How a Holistic ESP Design for Deep Deviated Wells with Low Flow Rates Achieved Economic Production

2021 ◽  
Author(s):  
Lawrence Camilleri ◽  
Jorge Luis Villalobos ◽  
Pedro Luis Escalona ◽  
Alvaro Correal ◽  
Carlos Reyes ◽  
...  
Keyword(s):  
Historical Review ◽  
Substantial Improvement ◽  
Operating Conditions ◽  
Gas Content ◽  
Low Flow ◽  
Flow Rates ◽  
Artificial Lift ◽  
Electrical Submersible Pumps ◽  
Deviated Wells

Abstract The Shaya wells have vertical depths of 11,000 ft and are heavily depleted. They, therefore, require 10,000 ft of lift to achieve the target drawdown. Electrical submersible pumps (ESPs) were deployed, but because of the low flow rates (80 B/D), produced solids, and high free gas content, initial run lives were uneconomical. This 47-well case study demonstrates how a holistic design and operating procedure achieved both the target drawdown and an economical mean time between failure (MTBF). "Learning from history" was the key method as there was sufficient ESP data to determine the root cause of ESP failures based on a combination of dismantle inspection and failure analysis (DIFA) and operating conditions. Moreover, production testing combined with real-time downhole gauge data enabled inflow characterization with both nodal and pressure transient analysis, thereby establishing the well potential and ensuring that the new proposed design was not only reliable but also achieved the targeted drawdown. An additional requirement was to handle both the current low rates and higher rates associated with future waterflooding. A historical review of 9 wells was conducted, followed by a new ESP design that was proposed and installed in 47 wells, which achieved an MTBF of over 940 days, whereas previous designs in the same wells had an MTBF of only 650 days. This substantial improvement was achieved without compromising drawdown as the wells were produced with a flowing intake pressure of approximately 250 psia at setting depths of 9,500 ft. This result is particularly noteworthy when one considers the harshness of the well conditions and, in particular, bottom-hole temperatures of 240°F, fines migration, deviated wells with doglegs above 2.5°/100ft, intake pressures below bubble point and low productivity indices (PIs) of 0.2 B/D/psi. The high depletion combined with low PIs, which resulted in very low flow rates of as low as 50 B/D, was the most challenging factor of this application. Outflow modeling and wellbore hydraulics were also important considerations to limit solid fallback due to insufficient velocity in the production tubing as well minimize heat rise caused by startup transients, which can be long in low-PI wells. ESPs are traditionally best suited to wells with liquid rates providing sufficient cooling for both the motor and the pump as well as short unloading transients during startup. This success story, therefore, provides an important reference for future ESP applications in very low flow rates in deep wells, which are beyond the recommended application envelope of alternative low flow rate artificial lift solutions such as progressive cavity pumps and sucker rod pumps.

Experimental Investigation of Spray Cooling Heat Transfer on Circular Grooved Surface

2017 ◽  
Author(s):  
Azzam S. Salman ◽  
Jamil A. Khan
Keyword(s):  
Heat Transfer ◽  
Flow Rate ◽  
Cooling System ◽  
Volumetric Flow Rate ◽  
Target Surface ◽  
Spray Cooling ◽  
Operating Conditions ◽  
Low Flow ◽  
Inlet Temperature ◽  
Flow Rates

An experimental study was conducted in a closed loop spray cooling system working with deionized water as a cooling medium, to investigate the effects of surface modification on the spray cooling heat transfer enhancement in the single-phase region. Plain copper surface with diameter 1.5 cm and an enhanced surface with circular grooves were tested under different operating conditions. The volumetric flow rate of the coolant ranged from 115 mL/min to 177 mL/min., and the water inlet temperature was kept between 21–23 °C. Also, the distances between the nozzle and the target surface were varied at 8, 10, and 12 mm respectively. The results show that the distance between the nozzle and the target surface did not have a significant effect on the heat transfer performance for the low flow rates, while it has a slight effect on high flow rates for both surfaces. Also, increasing the liquid volumetric flow rate increases the amount of heat removed, and the heat transfer coefficient for both surfaces. Moreover, the maximum enhancement ratios achieved were 23.4% and 31% with volumetric flow rates of 153 mL/min, and 177 mL/min respectively.

scholarly journals Novel hot-wire based spirometry is highly accurate at low flow rates

2018 ◽  
Vol 4 (1) ◽  
pp. 513-515 ◽  
Author(s):  
Arshan Perera ◽  
Petra Friedrich ◽  
Rosina Ledermüller
Keyword(s):  
Comparative Study ◽  
Pulmonary Function ◽  
Pulmonary Function Test ◽  
Measurement Accuracy ◽  
Differential Pressure ◽  
Low Flow ◽  
Hot Wire ◽  
Flow Rates ◽  
Low Flows ◽  
Function Test

AbstractSpirometry is the most commonly used pulmonary function test. The aim of this comparative study was to evaluate four commercially available spirometers with different measurement principles (turbine-, ultrasound-, differential pressure- and hot-wire anemometer). In particular, the measurement accuracy in breathing manoeuvres with low flow rates was investigated, which is highly relevant for paediatric use. Among the tested devices the hot-wire based spirometer showed the highest measurement accuracy at low flows whilst fully complying with the ATS/ERS standards.

Experimental and Numerical Study on Hydraulic Performances of a Turbopump With and Without an Inducer

2018 ◽  
Author(s):  
Yanxia Fu ◽  
Meng Fan ◽  
Giovanni Pace ◽  
Dario Valentini ◽  
Angelo Pasini ◽  
...  
Keyword(s):  
Total Pressure ◽  
Pressure Rise ◽  
Hydraulic Performance ◽  
Numerical Results ◽  
Operating Conditions ◽  
Design Flow ◽  
Low Flow ◽  
Flow Rates ◽  
Lower Flow ◽  
Inlet Duct

The hydraulic performance of a centrifugal turbopump with and without a 3-bladed axial inducer has been studied both experimentally and numerically. A 3D numerical model has been used to simulate the flow through from the inlet to the outlet ducts of the turbopump with and without an inducer using the ANSYS CFX code. The sensitivity of the numerical results has been analyzed with reference to the adopted turbulent flow models, to the length of the input and output ducts included in the simulations, to the reference positions used for the evaluation of the total pressure rise and to the temperature of the operating fluid. The measured and predicted hydraulic performances of the turbopump with and without the inducer have been compared under different operating conditions. As expected, the predicted hydraulic performance of the turbopump is significantly influenced by the lengths of the inlet and outlet ducts, the turbulence models and, at low flow rates, the reference positions of the total pressure rise measurements. The pressure rise coefficients obtained from the simulations using an inlet duct with length of 3 rTi and 10 rTi were significantly lower than the experimental results, while at low flow rates those referring to the inlet duct with length greater than 10 rTi were significantly higher than those obtained for the shorter inlet duct. With reference to the effect of the pressure measurement locations, the difference between the numerical results of the pressure rise coefficient and the experimental values was much higher when the data were obtained at the locations where the transducers was mounted in the experimental tests at lower flow rates. Moreover, the hydraulic performance of the turbopump at lower flow rates can be significantly influenced by the use of the upstream inducer, with a pressure drop of 20% in particular at 60% of the design flow rate.

scholarly journals Effects of network pressure on water meter under-registration: an experimental analysis

2013 ◽  
Vol 6 (1) ◽  
pp. 119-149 ◽  
Author(s):  
C. M. Fontanazza ◽  
V. Notaro ◽  
V. Puleo ◽  
G. Freni
Keyword(s):  
Laboratory Experiments ◽  
Operating Conditions ◽  
Low Flow ◽  
Consumption Pattern ◽  
Water Supply Systems ◽  
Flow Rates ◽  
Systemic Error ◽  
Starting Flow ◽  
Water Meters ◽  
Water Meter

<p><strong>Abstract.</strong> In water supply systems, a considerable amount of apparent loss is caused by meter under-registration. Water meters are subject to intrinsic systemic error depending on the actual flow rates passing through them. Furthermore, the moving parts of the meter are subject to wear and tear that progressively reduce meter accuracy. The increase in systemic error is especially evident at low flow rates because of growing friction in the rotating mechanism, which requires a higher flow to start the meter (starting flow). The aim of this paper is to experimentally investigate metering error in an attempt to find a direct link between meter age, network pressure and apparent losses caused by the inability of the meter to accurately register the volume passing though it at low flow rates. The study was performed through laboratory experiments in which worn-out water meters were tested using a test bench. The results of the laboratory experiments show that ageing and pressure are both relevant parameters for determining meter starting flow. These results were then applied to assess the effects on apparent losses of the age of the meter, varying pressure values upstream of the meter (the pressure in the network where the meter is installed) and different patterns of flow rates passing through the device (the consumption pattern of the user). The presented results are useful for understanding the effects of operating conditions on water meter under-registration, which can aid water managers in implementing effective replacement campaigns.</p>

scholarly journals Confinements regulate capillary instabilities of fluid threads

2019 ◽  
Vol 873 ◽  
pp. 816-834 ◽  
Author(s):  
Xiaodong Chen ◽  
Chundong Xue ◽  
Guoqing Hu
Keyword(s):  
Capillary Pressure ◽  
Flow Rate ◽  
External Flow ◽  
The Other ◽  
Low Flow ◽  
Critical Conditions ◽  
Flow Rates ◽  
Confined Fluid ◽  
Capillary Instabilities ◽  
Stop Flow

We study the breakup of confined fluid threads at low flow rates to understand instability mechanisms. To determine the critical conditions between the earlier quasi-stable necking stage and the later unstable collapse stage, simulations and experiments are designed to operate at an extremely low flow rate. The critical mean radii at the neck centres are identified by the stop-flow method for elementary microfluidic configurations. Two distinct origins of capillary instabilities are revealed for different confinement situations. One is the gradient of capillary pressure induced by the confinements of geometry and external flow, whereas the other is the competition between the capillary pressure and internal pressure determined by the confinements.

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