Showing papers on "Volumetric flow rate published in 1996"

Optimizing and Predicting CHF in Spray Cooling of a Square Surface

Abstract: Spray cooling of a hot surface was investigated to ascertain the effect of nozzle-to-surface distance on critical heat flux (CHF). Full cone sprays of Fluorinert FC-72 and FC-87 were used to cool a 12.7 X 12.7 mm 2 surface. A theoretical model was constructed that accurately predicts the spray's volumetric flux (liquid volume per unit area per unit time) distribution across the heater surface. Several experimental spray sampling techniques were devised to validate this model. The impact of volumetric flux distribution on CHF was investigated experimentally. By measuring CHFfor the same nozzle flow rate at different nozzle-to-surface distances, it was determined CHF can be maximized when the spray is configured such that the spray impact area just inscribes the square surface of the heater. Using this optimum configuration, CHF data were measured over broad ranges of flow rate and subcooling, resulting in a new correlation for spray cooling of small surfaces.

LPCVD silicon‐rich silicon nitride films for applications in micromechanics, studied with statistical experimental design*

Abstract: A systematic investigation of the influence of the process parameters temperature, pressure, total gas flow, and SiH2Cl2:NH3 gas flow ratio on the residual stress, the refractive index, and its nonuniformity across a wafer, the growth rate, the film thickness nonuniformity across a wafer, and the Si/N incorporation ratio of low pressure chemical vapor deposition SixNy films has been performed. As a tool for complete characterization of the property-deposition parameter relations, a full factorial experimental design was used to determine the dominant process parameters and their interactions. From this study it could be concluded that, in decreasing order of importance, the gas flow ratio of Si and N containing precursors, temperature, and pressure are the most relevant parameters determining the mechanical and optical properties of the films and the deposition rate and nonuniformity in film properties across a wafer. The established relations between properties and deposition parameters were fitted with physical–chemical models, including a film growth model based on a Freundlich adsorption isotherm. The optimal deposition conditions for films to be used in micromechanical devices will be discussed.

Experimental investigation of heat transfer in a horizontal tube falling film absorber with aqueous solutions of LiBr with and without surfactants

Abstract: To learn about the physical background of the absorption process, the accompanying heat transfer was studied experimentally. A horizontal tube heat exchanger, similar to commercial absorbers, was built. Two different types of tubes were tested, one with a plain, the other with a knurled surface. The solution volume flow, the temperatures of the cooling water and of the solution, and the concentration of the solution were varied to search for correlations of the heat-transfer coefficient with the physical properties of the solution. The heat-transfer coefficients decrease with increasing viscosity and augmenting surface tension. They also depend on the fluid regime of the solution film, i.e. they increase with growing solution volume flow. The influence of two surfactants — 1-octanol and 2-ethyl-1-hexanol in various concentrations — on the absorption process was examined quantitatively. An increase of 60–140% was measured for the heat-transfer coe coefficients.

Method of compensating for changes in flow characteristics of a dispensed fluid

Abstract: A fluid dispensing control for controlling the dispensing of a fluid by a metering valve through a nozzle onto a workpiece. An initial value of a flow characteristic of the fluid is determined that is correlated to the relationship between the flow rate of the fluid and nozzle pressure. Desired nozzle pressure values are periodically determined by evaluating a model of flow rate of the fluid through nozzle in response to the initial value of the flow characteristic and a desired flow rate value. Thereafter, the control provides command signals to the metering valve as a function of the desired nozzle pressures. A new value of the flow characteristic is determined as a function of the measured volume of fluid dispensed during the dispensing cycle to the measured nozzle pressure. During a subsequent dispensing cycle, the control determines the desired nozzle pressures by evaluating the model of flow rate of the fluid through the nozzle as a function of the new value of the flow characteristic. The process of reevaluating the flow characteristic over successive dispensing cycles as a function of measured volumes of fluid dispensed and measured nozzle pressures, and using those updated values to reevaluate the model of flow rate of fluid through the nozzle, is repeated.

Effect of Laminar Flow in Capillary Electrophoresis: Model and Experimental Results on Controlling Analysis Time and Resolution with Inductively Coupled Plasma Mass Spectrometry Detection

Abstract: A capillary electrophoresis model was modified to include the effect of laminar flow. Experimental results using inorganic ions with a wide range of mobilities were compared to model predictions. The effect of laminar flow rate on analysis time, peak widths, peak asymmetry, and electrophoretic resolution is discussed. The laminar flow rate in the electrophoresis capillary was controlled by regulating the sheath flow rate in a concentric nebulizer interface. Laminar flow in the direction of the detector allows the analysis of positive, neutral, and negative species, all in one electrophoretic run, in less than 2 min. By increasing the sheath electrolyte flow rate, laminar flow in the electrophoresis capillary can be eliminated, resulting in increased resolution at the expense of an increase in analysis time. At higher sheath flow rates, laminar flow is generated in the electrophoresis capillary in the direction away from the detector to further retard the migration of charged species. When concentration ov...

Automatic well test system and method of operating the same

Abstract: An automatic well test system (20) utilizes a Coriolis flowmeter (68) that functions as a mass flowmeter and densitometer in combination with a water-cut monitor (66) to calculate volumetric flow rates and densities of materials draining from a test separator (24) in a combined or two-phase production stream. An oil-phase density value is corrected to eliminate the effect of its water content, and divided into the mass flow rate reading to obtain a net oil flow rate. System operations are governed by an automated controller (86) that utilizes a gas blanket system (28) to prevent low pressures from liberating gas from the liquids within the test separator.

Pressure-based mass flow controller

Abstract: A pressure-based mass flow controller suitable for accurately monitoring and controlling the flow of many types of precursors characterized by vapor pressures ranging from approximately 2 torr or lower to at least 760 torr or higher at delivery temperatures of up to at least 250 degrees C. or higher for flow rates ranging from molecular to sonic. A flow restrictive element is installed in the precursor flow path, and the pressures of the fluid upstream and downstream of the flow restrictive element are measured. The ratio of the upstream and downstream fluid pressures is computed and compared to a value stored in the memory of a CPU associated with the controller to determine whether the flow is choked or non-choked. The mass flow of the precursor fluid is then computed by the CPU in accordance with a linear function of the upstream pressure, for choked flow, and in accordance with a nonlinear function of both the upstream and downstream pressures, for non-choked flow.

Flow measurement compensation technique for use with an averaging pitot tube type primary element

Abstract: A transmitter in a process control system for measuring flow rate measures total pressure (P TOT ) and differential pressure (h) of process fluid flowing through a process pipe. The static pressure (P STAT ) is determined based upon the total pressure (P TOT ). The calculated static pressure is used to determine the fluid density (ρ) and the gas expansion factor (Y 1 ) of the process fluid flowing in the pipe. This information is used to calculate flow rate (Q) of the process fluid.

Method of determining a characteristic of a fluid

Abstract: A method of determining a characteristic of a fluid involves measuring a sonic transit time (102), along a non-perpendicular path, through the fluid. The sonic transit time is used to determine a speed of sound in the fluid (104). A measured flow rate (106) is determined from the sonic transit time. A friction factor (108) is calculated using the speed of sound and the measured flow rate. Next, a velocity profile (110) is determined using the friction factor. Finally, an adjusted flow rate is calculated (112) using the velocity profile.

Stokes slip flow between corrugated walls

Abstract: Stokes flow between corrugated plates in microdomains has been analyzed using a perturbation method. This approach used the incompressible Navier-Stokes equations, but the velocity-slip is present along the solid-fluid interface. For the slip flow regime, if we introduce Knudsen number (Kn) herein, 0.01 ≤Kn≤ 0.1, the total flow rate is increasing as a ratio of 1 + 6Knto no-slip Stokes flow. If we consider fixedKncases, the corrugations still decrease the flow rate, consideringO(e2) terms, and the decrease is maximum as the phase shift becomes 180 °.

Ultrasonic fraction and flow rate apparatus and method

Abstract: Disclosed is a method for measuring the amount of liquid in a volume of gas and the associated flow rates. A method of determining the percentage of a liquid present in a volume of gas is provided. The method comprises the steps of impressing the volume of gas with ultrasonic energy, receiving the ultrasonic energy impressed upon and traversing the volume of gas, measuring the received ultrasonic energy which has traversed the volume of gas, evaluating various parameters of the measured ultrasonic energy for variations which variations are a function of the liquid fraction in the volume of gas. A method is provided for determining the flow rates associated with a liquid-gas mixture.

Experimental study and modeling of oscillating flow of high density polyethylenes

Abstract: The influence of flow rate and die geometry on the observable flow rate/pressure relationship of a linear high density polyethylene is investigated using a capillary rheometer. The experimental results are applied to an adapted version of the relaxation–oscillation model proposed by Molenaar and Koopmans for describing the oscillating flow regime. The current model allows for a quantitative description of the hysteresis cycle in the oscillating flow regime in terms of the main experimental variables, such as imposed flow rate, reservoir (barrel) volume, and material compressibility.

A mechanistic model for computing fluid temperature profiles in gas-lift wells

Abstract: In a continuous-flow gas-lift operation, gas is injected down the annulus into the tubing near the top of perforations. The intrinsic idea is to aerate the liquid column, thus providing the necessary stimulus for fluid flow. Because the volumetric gas rate is dependent upon both the pressure and temperature at the depth of injection, accurate knowledge of these entities cannot be overemphasized for an efficient lift. In particular, the behavior of the nitrogen gas charged in the dome is critically dependent upon the temperature prediction for the optimal performance of the bellows-charged gas-lift valves. Current practice entails use of a linear temperature profile for the annular fluid while applying empirical correlations for the tubing fluids. Improved temperature predictions are now possible for fluids in both conduits by modeling the heat and fluid flow problem at hand from first principles. In this work, they present a mechanistic model for the flowing temperature of the annular gas and the gas/liquid two-phase mixture in the tubing as a function of both well depth and production time, regardless of the well deviation angle. The model is based on energy balance between the formation and fluids flowing through each conduit. While flowing down the annulus,more » the cold gas injected at the wellhead continues to gain heat. The heat-transfer rate for the annular gas depends on the relative temperatures of the formation and the tubing fluid. They assume unsteady-state heat transfer in the formation and steady-state heat transfer in the tubular for a continuous-flow gas-lift operation.« less

A multicomponent, multitemperature model for high density plasma processing reactors

Abstract: We present a coupled model for neutral transport and charged species dynamics in high density plasma processing reactors. The model consists of conservation equations for mass, momentum, and energy within a multicomponent, multitemperature framework. The radially averaged one‐dimensional model is applied to an electron cyclotron resonance CF4 discharge and results are presented for various pressures and flow rates. The pressure drop in the reactor is found to be significant compared to the pressure itself in high density, low pressure reactors which affects the plasma, and flow characteristics significantly. The nature of the viscous pressure drop in the reactor is also confirmed by two‐dimensional fluid dynamics simulations of only the gas flow.

Predicting gas-condensate reservoir performance: how flow parameters are altered when approaching production wells

Abstract: Describing flow processes occuring both far from and close to the wellbore region is a major concern to accurately predict gas-condensate reservoir performance. This requires the knowledge of the gas-condensate parameters, e.g. the critical liquid saturation Slc and the gas-condensate relative permeabilities krg and krl. Regarding their determination, this paper addresses two main questions: (1) Can analog fluid systems be used instead of real ones to measure gas-condensate flow parameters ? (2) What flow rate dependence must the relative permeabilities account for to properly describe the high flow rate conditions that prevail in the wellbore region ? To acquire flow parameters representative of the inner part of the reservoir, an integrated procedure was used to measure Slc's and kr curves. 29 flow tests were performed in an outcrop clayey sandstone core and 2 in an outcrop chalk core, using as gas-condensate systems, a binary C1C3, a ternary C1C3C7 and finally an actual North Sea reservoir fluid. Slc's for both analog and real fluid systems were found to increase with γ. For relative permeabilities under the low flow rate conditions that were used, no γ dependence of the kr curves was put into evidence. This was explained on the basis of a dependence upon a macroscopic capillary number CA that allows to compare viscous to capillary forces. Using this dimensionless number and considering a CA - dependence of the relative permeabilities leads to reconcile variations of relative permeabilities with y and flow rate as described in the literature. Finally, this paper discusses what characteristics relative permeabilities should display so as to properly model wellbore flow conditions.

Gas Migration in MX80 Buffer Bentonite

Abstract: Controlled flow-rate gas injection experiments have been performed on pre-compacted samples of KBS-3 specification Mx80 buffer bentonite using helium as a safe replacement for hydrogen. By simultaneously applying a confining pressure and backpressure, specimens were isotropically-consolidated and fully water-saturated under pre-determined effective stress conditions, before injecting gas using a syringe pump. Ingoing and outgoing gas fluxes were monitored. All tests exhibited a conspicuous threshold pressure for breakthrough, somewhat larger than the sum of the swelling pressure and the backpressure. All tests showed a post-peak negative transient leading to steady-state gas flow. Using a stepped history of flow rate, the flow law was shown to be nonlinear. With the injection pump stationary (i.e., zero applied flow rate), gas pressure declined with time to a finite value. When gas flow was reestablished, the threshold value for gas breakthrough was found to be significantly lower than in virgin clay. There is strong evidence to suggest that the capillary pressure for the penetration of interparticle pore space of buffer bentonite is of such a magnitude that normal two-phase flow is impossible. Gas entry and breakthrough is therefore accompanied by the development of microcracks which propagate through the clay from gas source to sink. Themore » experiments suggest that these pathways open under high gas pressure conditions and partially close if gas pressure falls, providing a possible explanation of the nonlinearity of the flow law.« less

Model Studies of Liquid Flow in the Blast Furnace Lower Zone

Abstract: The non-wetting flow of liquid iron in the blast furnace lower zone is simulated experimentally using a two dimensional raceway model with water, air and 4.1 mm diameter polyethylene beads to represent liquid iron, blast furnace gas and the coke bed respectively. An X-ray technique is used to visualise liquid flow in the packed bed and the distribution of liquid from the bottom of the bed is measured. The liquid percoates through the packed bed as series of rivulets which are continuously breaking up and rejoining. The direction and magnitude of the percolation velocity is determined by the balance between three forces acting on the liquid-gravity, gas drag and bed resistance. The gas drag has a very strong effect on the liquid distribution, forcing the liquid away from the raceway region. This effect increases with increasing gas flow rate. At high gas flow rate, the liquid flow rate and distribution at the top of the bed do not effect the liquid distribution leaving the bed. Near the raceway, the packed bed is dry. The size of the dry region increases with increasing gas flow rate. Above the raceway, beyond the dry packed bed, is a region of high liquid holdup. Liquid dripping into this region has a high residence time compared to liquid falling through the deadman zone. A mathematical model for liquid fow is outline which gives good agreement with experimentally observed liquid flow patterns in the cold raceway model and could be suitable for predicting the liquid flow pattern under real blast furnace conditions. This study confirms that the effect of gas drag on the flow of liquid iron through the blast furnace lower zone is important and should not be neglected.

Apparatus for the purification of liquids and a method of manufacturing and of operating same

Abstract: A method of manufacturing an apparatus for the electrodeionization of a fluid includes determining the flow rate of the fluid to be deionized, its initial concentration of ionic impurities, a desired post-processing concentration of ionic impurities and appropriately selecting the number of diluting compartments for use in the apparatus and the electrical current to be applied between the anode and cathode in the apparatus and manufacturing the apparatus accordingly. A method of operating an apparatus for electrodeionization of a fluid includes monitoring the concentration of ionic impurities of the fluid to be deionized, monitoring the concentration of ionic impurities of the fluid which has been processed by the apparatus, determining the flow rate of the fluid to be deionized and altering the electrical current applied between the anode and cathode to maintain a predefined relationship between the drop in the concentration of ionic impurities of the fluid through the apparatus and the electrical current and the flow rate within a selected range of values. A novel electrodeionization apparatus includes an electrodeionization core, means for determining the concentration of the ionic impurities of fluid to be processed within the apparatus, a means for determining the concentration of the ionic impurities conductivity of fluid which has been processed within the apparatus, a measuring device to determine the flow rate of fluid processed by the apparatus, a current sensing device to measure the electrical current applied to the anode and cathode and a control device to process these values and to alter the electrical current applied to the anode and cathode of the apparatus to maintain a predefined ratio between the measured values within a selected range of values.

A flow analysis system with an amperometric detector for the determination of hydrogen sulphide in waters

Abstract: A flow analysis system with an amperometric H2S detector and a gas extraction unit as well as an integrated coulometric calibration unit is described, which allows an on-line determination of hydrogen sulphide in aquatic samples. By variation of different parameters (e.g. flow rate, gas injection volume, pH of solution) a wide dynamic working range of concentrations from 1 μmol/l H2S to 750 μmol/l is accessible. The sampling rate is about 36 samples h−1 using an average flow rate of 1.78 ml/min and a gas injection volume of 28 μl. The measuring system is designed as a portable device. In combination with the polyethylene-tube of a PTFE-underwater pump field-measurements on board are possible.

Identification of Pool Boiling Heat Transfer Mechanisms From a Wire Immersed in Saturated FC-72 Using a Single-Photo/LDA Method

Abstract: A unique method to determine the vapor volumetric flow rate above a heated wire utilizing a single photograph and laser-Doppler anemometry is developed and discussed. The volumetric flow rate is combined with additional analyses to determine the overall contributions to the total heat flux from four nucleate boiling heat transfer mechanisms (latent heat, natural convection, Marangoni flow, and microconvection). This method is applied to a 75-μm wire immersed in a saturated, highly wetting liquid (FC-72). Latent heat is identified as the dominant mechanism in the fully developed nucleate boiling regime.

Phosphorus doping of Si and Si1−xGex grown by ultrahigh vacuum chemical vapor deposition using Si2H6 and GeH4

Abstract: 100 ppm PH3 diluted in hydrogen is used as the n‐type dopant gas in Si and Si1−xGex epilayers grown by ultrahigh vacuum chemical vapor deposition (UHVCVD) using Si2H6 and GeH4. The phosphorus concentration in Si increases linearly at a small PH3 flow rate and becomes nearly saturated at higher flow rates, while the phosphorus concentration in Si1−xGex only shows a nearly linear behavior with PH3 flow rate. The growth rates of Si and Si1−xGex epilayers decrease seriously (∼50%) and slightly (∼10%) with the increase of PH3 flow rate, respectively. These results can be explained by a model based on the enhancement of hydrogen desorption rate at smaller PH3 flow rates and different levels of the effects of phosphorus blocking of surface‐activated sites between Si and Si1−xGex epilayers at higher PH3 flow rates.

The Onset of Flow Instability for Downward Flow in Vertical Channels

Abstract: A simple analytical model to predict the onset of Ledinegg instability in vertical channels under downflow conditions has been developed and evaluated. The model divides the flow field into three regions based upon the fluid temperature. The pressure drop is then found by solving an appropriate set of equations for each region. The theoretical results are compared to an extensive set of experimental data covering a range of channel diameters and operating conditions. Agreement is excellent, and the prediction of the velocity at which the minimum point in the demand curve occurs is within 12 percent over the range of experimental results. A parameter, the ratio between the surface heat flux and the heat flux required to achieve saturation at the channel exit for a given flow rate, is found to be a very accurate indicator of the minimum point velocity.

Random Excitation Forces in Tube Bundles Subjected to Two-Phase Cross-Flow

Abstract: Data from two experimental programs have been analyzed to determine the characteristics of the random excitation forces associated with two-phase cross-flow in tube bundles. Large-scale air-water flow loops in France and Canada were used to generate the data. Tests were carried out on cantilevered, clamped-pinned, and clamped-clamped tubes in normal-square, parallel-triangular, and normal-triangular configurations. Either strain gages or force transducers were used to measure the vibration response of a centrally located tube as the tube array was subjected to a wide range of void fractions and flow rates. Power spectra were analyzed to determine the effect of parameters such as tube diameter, frequency, flow rate, void fraction, and flow regime on the random excitation forces. Normalized expressions for the excitation force power spectra were found to be flow-regime dependent. In the churn flow regime, flow rate and void fraction had very little effect on the magnitude of the excitation forces. In the bubble-plug flow regime, the excitation forces increased rapidly with flow rate and void fraction.

Reactions of polyethylene surfaces with the downstream products of an air plasma: Gas phase and surface spectroscopic studies

Abstract: The gas phase downstream products of an air glow discharge have been measured, using absorption and emission spectroscopies, as a function of plasma power, air flow rate, and distance from the plasma. In addition, the reaction of these products with a linear low density polyethylene (LLDPE) polymer surface has been followed using x-ray photoelectron spectroscopy (XPS). At higher air flow rates (>300 sccm), the primary reactive species is confirmed to be O( 3 P) atomic oxygen. Some O( 3 P) is generated in the plasma itself, but more appears to be formed in the downstream region, because of dissociation of molecules in their excited states. At low flow rates, the concentration of O( 3 P) is strongly depleted at the sample position, but other atomic oxygen states become more prominent. O( 5 S) and O( 3 S) are two states which are identified. XPS studies of the polyethylene surface reacted at high flow rates shows oxygen functionalities that are likely the result of an initiation by hydrogen abstraction. At low flow rates, the products suggest initiation by oxygen insertion. Thus, changes in flow rate can result in major changes to the polymer surface chemistry.

Numerical simulation of three-dimensional fluid flow and mixing process in gas-stirred ladles

Abstract: A numerical study was performed for the three-dimensional turbulent fluid flow and mixing characteristics in gas-stirred ladles with a code developed by present authors. The effects of gas flow rate, positions of nozzle and tracer, and inclined wall on the flow pattern and mixing were investigated in the present work. It is shown that eccentric blowing increases the azimuthal velocity, thus reducing the mixing time, and the mixing time is sensitive to the alloy/tracer adding position especially for center blowing. For the ladle with inclined wall, it has shorter mixing time compared with the cylindrical one. The predicted results were compared with the experimental data, which showed good quantitative agreements.