The Effects of Fluid Properties on Cavitation in Centrifugal Pumps

1965 ◽  
Vol 87 (3) ◽  
pp. 309-318 ◽  
Author(s):  
W. A. Spraker
Keyword(s):  
Cold Water ◽  
Fuel Oil ◽  
Centrifugal Pumps ◽  
Hydrocarbon Mixtures ◽  
Volume Percentage ◽  
Cavitation Process ◽  
Pure Fluids ◽  
Two Fluids ◽  
Fluid Properties ◽  
The Difference

An analytical model of the cavitation process in a pump is developed assuming that the flow is adiabatic, frictionless, steady, and irrotational. A relationship is developed relating the volume percentage of the fluid vaporized during the cavitation process to the “thermal cavitation parameter.” Two assumptions are then introduced concerning the cavitation process in a pump pumping fluids of different cavitation characteristics. Using these assumptions, a relationship is derived indicating that the difference in net positive suction head (NPSH) of a given pump handling two fluids is a function of the difference of the reciprocals of the thermal cavitation parameter for the two fluids and of the volume percentage of the fluid vaporized. This relationship is compared with data describing the cavitation characteristics of six pumps handling four pure fluids. The change in NPSH for all of the pumps and fluids, using the cold-water NPSH as a reference, is found to correlate as a function of the reciprocal of the thermal cavitation parameter with an accuracy of ±1 ft in NPSH. Experimental and analytical methods for determining the cavitation characteristics of pumps handling petroleum-based hydrocarbon mixtures are then described. Cavitation data for two pumps handling gasoline, fuel oil, and crude oil are presented. The data correlation for pure fluids is extended to include cavitation data for petroleum-based hydrocarbon mixtures. It is found that mixtures exhibit an additional decrement in NPSH over that for pure fluids having the same value of the thermal cavitation parameter. This additional decrement is found to be temperature dependent.

Cavitation and NPSH Requirements of Various Liquids

1959 ◽  
Vol 81 (2) ◽  
pp. 167-174 ◽  
Author(s):  
Victor Salemann
Keyword(s):  
Direct Measurement ◽  
Cold Water ◽  
Test Results ◽  
Centrifugal Pumps ◽  
Pump Performance ◽  
Cavitation Process

Test results on the net positive suction head, NPSH, requirements for centrifugal pumps handling water up to 420 F, some hydrocarbons, and Freon-11 are presented. Satisfactory pump performance was observed with net positive suction heads less than those required by the pump on cold water. A direct measurement of NPSH was attempted and is reported. The cavitation process is discussed and a correlation and method of prediction for all liquids is proposed.

STUDIES ON HABITUATION TO COLD PAIN

1966 ◽  
Vol 44 (2) ◽  
pp. 287-293 ◽  
Author(s):  
Jacques LeBlanc ◽  
Pierre Potvin
Keyword(s):  
Cold Water ◽  
Mental Arithmetic ◽  
Blood Pressure Response ◽  
Human Subjects ◽  
Cold Pain ◽  
Left Hand ◽  
Water Test ◽  
The Difference ◽  
The Right ◽  
Habituation To Cold

It was possible to produce habituation to cold in a group of human subjects by immersing the left hand in cold water for [Formula: see text] minutes twice a day for 19 days. The right hand did not adapt. Another group of subjects was exposed similarly with the difference that an anxiety test (mental arithmetic test) was always given simultaneously with the cold-water test. In this second group the original blood pressure response, i.e. for the first day, was greater than in the first group because of the cumulative effects of the two tests. After 19 days definite evidence was obtained for adaptation to these two tests administered together. However, when these tests were given separately to the second group, no adaptation was evident; adaptation occurred only to both tests given simultaneously. These results indicate that no adaptation develops to cold per se if the subjects are distracted from cold discomfort. It was also found that adaptation of one hand to cold water not only failed to induce adaptation in the opposite hand but even reinforced responses of the unadapted hand. These findings suggest a participation of the central nervous system in adaptation to cold pain, and tend to minimize the importance of local peripheral changes.

Pump Performance Improvement by Restraining Back Flow in Screw-Type Centrifugal Pump

2005 ◽  
Vol 127 (4) ◽  
pp. 755-762 ◽  
Author(s):  
Yasushi Tatebayashi ◽  
Kazuhiro Tanaka ◽  
Toshio Kobayashi
Keyword(s):  
Pressure Fluctuations ◽  
Centrifugal Pumps ◽  
Two Phase ◽  
Simple Method ◽  
Back Flow ◽  
Pump Performance ◽  
Impeller Outlet ◽  
Pump Head ◽  
The Difference ◽  
Set Up

The authors have been investigating the various characteristics of screw-type centrifugal pumps, such as pressure fluctuations in impellers, flow patterns in volute casings, and pump performance in air-water two-phase flow conditions. During these investigations, numerical results of our investigations made it clear that three back flow regions existed in this type of pump. Among these, the back flow from the volute casing toward the impeller outlet was the most influential on the pump performance. Thus the most important factor to achieve higher pump performance was to reduce the influence of this back flow. One simple method was proposed to obtain the restraint of back flow and so as to improve the pump performance. This method was to set up a ringlike wall at the suction cover casing between the impeller outlet and the volute casing. Its effects on the flow pattern and the pump performance have been discussed and clarified to compare the calculated results with experimental results done under two conditions, namely, one with and one without this ring-type wall. The influence of wall’s height on the pump head was investigated by numerical simulations. In addition, the difference due to the wall’s effect was clarified to compare its effects on two kinds of volute casing. From the results obtained it can be said that restraining the back flow of such pumps was very important to achieve higher pump performance. Furthermore, another method was suggested to restrain back flow effectively. This method was to attach a wall at the trailing edge of impeller. This method was very useful for avoiding the congestion of solids because this wall was smaller than that used in the first method. The influence of these factors on the pump performance was also discussed by comparing simulated calculations with actual experiments.

Design and Preliminary Testing of a Novel Dual-Chambered Syringe

2011 ◽  
Vol 5 (2) ◽  
Author(s):  
Karen May-Newman ◽  
Maria T. Matyska ◽  
Martin N. Lee
Keyword(s):  
Low Cost ◽  
Preliminary Test ◽  
Blood Stream ◽  
Medical Procedure ◽  
Dual Chamber ◽  
Two Fluids ◽  
Small Channel ◽  
Locking Mechanism ◽  
Fluid Properties ◽  
Balance Of Forces

Intravenous catheterization is the most common invasive medical procedure today and is designed to introduce medication directly into the blood stream. Common practice is to administer medicine with one syringe, followed by a saline flush to clear the line of any residual medication. The risk of infection due to the introduction of bacteria in the catheter hub is increased with the number of times the hub is accessed. In addition, the two-step process adds millions of nursing hours per year and is prone to error. The goal of this effort was to design and test a dual-chamber syringe that could be reliably used for both dispensing medicine and the saline flush, and be produced at a low cost. The syringe has a novel dual-chamber design with a proximal chamber for medicine and a distal chamber that contains saline. The saline chamber has a fixed volume when the handle is locked into position, which allows the handle to control the variable volume of the medicine chamber. Between the two chambers is a plunger that surrounds the small channel (which is an extension of the distal chamber) that separates the saline from the medicine. When the distal chamber is unlocked, the handle controls the volume of the saline chamber. By this mechanism, the syringe is able inject the medicine followed by the saline flush with a single access to the catheter hub. The smooth operation of the device relies on a locking mechanism to control the rear plunger and volume of the distal saline chamber, and a bubble plug residing in the small channel between the chambers that prevents mixing of the medicine and saline fluids. The bubble plug is held in place by a balance of forces that depend on geometric variables and fluid properties. The chosen design prevents mixing of the two fluids during the operation of the device, which was experimentally validated with mass spectrometry. The dual-chamber syringe has successfully achieved the design goal of a single syringe for the two-step catheter procedure of dispensing medicine and a saline flush. This novel design will reduce the potential for catheter-based infection, medical errors, medical waste, and clinician time. Preliminary test results indicate that this innovation can significantly improve the safety and efficiency of catheter-based administration of medicine.

Pump Performance Improvement by Restraining Back Flow in Screw-Type Centrifugal Pump

2005 ◽  
Author(s):  
Yasushi Tatebayashi ◽  
Kazuhiro Tanaka ◽  
Toshio Kobayashi
Keyword(s):  
Pressure Fluctuations ◽  
Centrifugal Pumps ◽  
Two Phase ◽  
Simple Method ◽  
Back Flow ◽  
Pump Performance ◽  
Impeller Outlet ◽  
Pump Head ◽  
The Difference ◽  
Set Up

The authors have been investigating the various characteristics of screw-type centrifugal pumps, such as pressure fluctuations in impellers, flow patterns in volute casings, and pump performance in air-water two-phase flow conditions. During these investigations, numerical results of our investigations made it clear that three back flow regions existed in this type of pump. Among these, the back flow from the volute casing toward the impeller outlet was the most influential on the pump performance. Thus the most important factor to achieve higher pump performance was to reduce the influence of this back flow. One simple method was proposed to obtain the restraint of back flow and so as to improve the pump performance. This method was to set up a Ring-like wall at the suction cover casing between the impeller outlet and the volute casing. Its effects on the flow pattern and the pump performance have been discussed and clarified to compare the calculated results with experimental results done under two conditions — namely, one with and one without this Ring-type wall. The influence of wall’s height on the pump head was investigated by numerical simulations. In addition, the difference due to the wall’s effect was clarified to compare its effects on two kinds of volute casing. From the results obtained it can be said that restraining the back flow of such pumps was very important to achieve higher pump performance. Furthermore, another method was suggested to restrain back-flow effectively. This method was to attach a wall at the trailing edge of impeller. This method was very useful for avoiding the congestion of solids because this wall was smaller than that used in the first method. The influence of these factors on the pump performance was also discussed by comparing simulated calculations with actual experiments.

scholarly journals Fluid Choice Based on Thermal Model and Performance Testing for Direct Cooled Electric Drive

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5867
Author(s):  
Robert Lehmann ◽  
Arthur Petuchow ◽  
Matthias Moullion ◽  
Moritz Künzler ◽  
Christian Windel ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Model ◽  
Performance Testing ◽  
Sensitivity Study ◽  
Maximum Heat ◽  
Cooling Fluid ◽  
Two Fluids ◽  
Fluid Properties ◽  
And Performance ◽  
Electric Traction

In this publication, the cooling fluid for direct oil-cooled electric traction drive is investigated. A dedicated thermal resistance model was developed in order to show the influence of the fluid properties on the continuous performance. For this purpose, the heat transfer parameters are adjusted in the simulation using an exponential approach in order to evaluate the cooling fluid. In a sensitivity study, density, heat capacity, thermal conductivity, and viscosity are investigated. Because viscosity, within the range investigated, shows the largest percentage deviation from the reference fluid, the greatest effect on performance can be seen here. In order to check the plausibility of the calculated results of the thermal simulation, two fluids were chosen for performance testing on a dedicated electro motor cooling (EMC) test. Beyond the investigation of heat transfer, aging of the defined fluid at maximum heat input over several hours is also evaluated. Only slight changes of the fluid properties are detected. This publication presents a thermal model for direct oil-cooled drive trains, which consider fluid properties. Furthermore, the model was tested for plausibility on real hardware.

EVALUATION OF SOME METHODS OF ANALYSIS FOR PETROLEUM HYDROCARBONS IN MARINE ORGANISMS

1975 ◽  
Vol 1975 (1) ◽  
pp. 115-121 ◽  
Author(s):  
John W. Farrington ◽  
Gilbert C. Medeiros
Keyword(s):  
Gas Chromatography ◽  
Soxhlet Extraction ◽  
Marine Organisms ◽  
Fuel Oil ◽  
Bay Area ◽  
Large Numbers ◽  
Significant Difference ◽  
The Difference ◽  
Replicate Measurements ◽  
Digestion Methods

ABSTRACT Soxhlet extraction, homogenization with Na2So4 in a Virtis homogenizer, and KOH-methanol digestion methods of extracting hydrocarbons from marine organisms have been tested and compared using subsamples of a clam (Marcenaria mercenaria) homogenate. The amounts of hydrocarbons were determined gravimetrically and the composition was partially characterized by gas chromatography. There was a statistically significant difference between the results of the Virtis vs. Soxhlet and Soxhlet vs. digestion methods. However, in practice the difference is small and would be apparent only if large numbers of replicate measurements were made. The concentration of hydrocarbons in clams from three locations, a polluted harbor area, a less polluted bay area, and a relatively clean bay have been determined. The composition was partially characterized by gas chromatography. Subsamples of clam homogenate spiked with 10 ppm API No. 2 fuel oil have been analyzed. Only 5 to 6 ppm of the spike were detected. Gas chromatographic analysis indicated that the lower molecular weight components of the spike were lost. The gas chromatographic passive tagging parameters were altered from those of the API No. 2 fuel oil by interference from hydrocarbons already present in the clams prior to spiking.

The Prediction of Volumes, Compressibilities and Thermal Expansion Coefficients of Hydrocarbon Mixtures

1968 ◽  
Vol 8 (02) ◽  
pp. 95-106
Author(s):  
Surjit M. Avasthi ◽  
Harvey T. Kennedy
Keyword(s):  
Thermal Expansion ◽  
Isothermal Compressibility ◽  
Absolute Deviation ◽  
Hydrocarbon Mixtures ◽  
Reservoir Performance ◽  
Thermal Expansion Coefficients ◽  
Isobaric Thermal Expansion ◽  
Volume Curve ◽  
Fluid Properties ◽  
Molal Volumes

Abstract An equation developed for gaseous hydrocarbon mixtures predicts molal volumes with an average absolute deviation of 0.73 percent when applied to 264 natural gas and condensate systems including 2,043 PVT points. Another equation developed for liquid hydrocarbon mixtures predicts molal volumes with an average absolute deviation of 1.12 percent when applied to 346 crude oil systems including 1,759 PVT points. Both equations require composition of the mixture to be expressed as mole fraction of methane through heptanes-plus, hydrogen sulfide, nitrogen and carbon dioxide, together with the characteristics of the heptanes-plus fraction in addition to the temperature and pressure. The equations cover wide ranges of the variables involved, and their accuracy is considerably better Than that of other available methods. The equations were differentiated to allow calculation of the coefficients of isothermal compressibility and isobaric thermal expansion. (In this paper the coefficient of isothermal compressibility and the coefficient of isobaric thermal expansion will be expressed as compressibility and thermal expansion coefficient, respectively.) Equations to calculate these quantities are presented. Introduction Calculations of reservoir performance for petroleum reservoirs require accurate knowledge of the volumetric behavior of hydrocarbon mixtures, both liquid and gaseous. Compressibilities are required in transient fluid flow problems, and thermal expansion coefficients are important in thermal methods of production. An accurate laboratory investigation of the PVT behavior of each reservoir fluid encountered would be costly and time consuming. For this reason various correlations for predicting fluid properties have been developed and recorded and recent literature. Correlations have been presented in the form of graphs, tables and equations. Since an increasing number of studies are being conducted with the aid of electronic computers, recent efforts have been directed toward development of correlations suitable for computer programming. Application of computers permits the use of more complex correlations which otherwise are not feasible. Moreover, methods for predicting reservoir performance, particularly those based on the compositional material balance, depend upon the capability of accurately expressing the molal volumes and other fluid properties as functions of pressure, temperature and composition. The coefficient of isothermal compressibility c is defined by(1) and can be computed from the slope of isothermal specific volume curve for each pressure. The compressibility is a point function and has the dimension of reciprocal pressure. The coefficient of isobaric thermal expansion beta is defined as(2) It is a point function and has the dimension of reciprocal temperature. The thermal expansion coefficient can be obtained from the slope of an isobaric specific volume curve for any temperature. SPEJ P. 95ˆ

Correlation of Cavitating Centrifugal Pumps

1984 ◽  
Vol 106 (2) ◽  
pp. 141-146 ◽  
Author(s):  
V. J. Zika
Keyword(s):  
Narrow Band ◽  
Centrifugal Pumps ◽  
Cavitation Process ◽  
New Methods ◽  
Thermodynamic Effect ◽  
Variable Nature ◽  
Test Points ◽  
Actual Test

The foreknowledge of the minimum NPSH (“net positive suction head”) required for a cavitation-free performance of centrifugal pumps is important for a safe and sound operation of these machines. The required NPSH varies from pump to pump, from fluid to fluid, and from temperature to temperature of the pumped fluid. This is known as the thermodynamic effect. The methods currently used for the correlation and analysis of this condition are not always reliable because of the multi-variable nature of the cavitation process. In this paper, two new methods are proposed which lead to more consistent correlations of the required minimum NPSH; thus they can also be used for more dependable predictions of the net positive suction head for any pump, fluid and temperature. The predictions by the two methods do not coincide, but outline a narrow band of probability, within which the actual test points are invariably located.

Defect Structures in Diamond Composite Coated Cemented Tungsten CarbideSubstrates

2011 ◽  
Vol 325 ◽  
pp. 339-344 ◽  
Author(s):  
Jim N. Boland ◽  
Xing S. Li ◽  
D. Hay ◽  
Colin M. MacRae ◽  
S. Elbracht ◽  
...  
Keyword(s):  
Wear Rate ◽  
Poor Quality ◽  
Wear Testing ◽  
Grinding Wheel ◽  
Sem Images ◽  
Volume Percentage ◽  
X Ray ◽  
Wear Rates ◽  
Valid Test ◽  
The Difference

Variability in the abrasive wear of PCD coatings on cemented WC substrates has been investigated. Six samples of PCD coated carbides were tested in a wear testing rig. The PCD coated element was used to turn an industry standard vitrified bonded corundum grinding wheel. The wear rate was measured as the weight loss of the cutting element per cubic metre of grinding wheel machined during the test. Two grades of cutting elements were observed. One grade had wear rates between 6 and 7.3 g/m³ but of the three poor quality samples, only one valid test was made realising wear rate of ~7,800 g/m³. The microstructures of the samples were studied using SEM, X-ray imaging, neutron diffraction and XRD. SEM images revealed differences in the volume percentage of diamonds in the two grades and the XRD scans highlighted the variable distribution of the diamond phase in the coating. Estimates of the residual stresses in a good and poor quality samples indicated significantly higher compressive stresses in the good quality versus poor quality coating. These results have revealed two extremes in the wear rates of these PCD coated carbides. It is suggested that the difference in diamond content between the two grades is not sufficient to account for the 3 orders-of-magnitude difference in the observed wear rates. However, the presence of intrusive veins of carbide material in the coatings, especially around the curved cutting tip, suggested that the macroscopic defects observed in the x-ray and SEM images were the major cause of the high wear rates in the poor quality sample.

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