Pressure Loss Measurements Research Articles

Centrifuge Modeling Study of Backward Erosion Piping with Variable Exit Size

This study presents the results from a series of centrifuge modeling tests conducted to investigate the backward erosion piping across a sandy foundation underlying an impervious cohesive layer with a defined exit hole. Different levels of centrifuge gravitational acceleration and various exit hole sizes were tested. The behavior at different phases of erosion was analyzed based on in-flight video recordings and posttest observations, along with local and global pressure loss measurements. Results showed that the overall mechanism that was modeled was similar to the mechanism described in previous small-scale experimental studies. The results showed that the exit hole size had minimal impact on the critical hydraulic gradient but affected the characteristics of the piping path and the amount of eroded material. The critical hydraulic gradient that initiated the erosion decreased slightly as the centrifuge gravitational acceleration increased. The values of the critical hydraulic gradient, which was studied locally and globally, ranged between 0.15 and 0.40, and fell within a range of estimates from typical analytical methods. This study provides a means to improve the testing protocol and analysis of centrifuge modeling of internal erosion mechanisms, which currently is limited in the literature.

Pressure loss of flexible ventilation ducts for residential ventilation: Absolute roughness and compression effect

The pressure loss of a duct affects the functionality of the ventilation equipment, the noise and especially the consumption of electricity to drive the fans. In addition, the pressure drop of the pipe is an important piece of information that serves to correctly design the ventilation system. The aim of the study is to determine the pressure drop of flexible hoses of relatively small diameters of 63–160 mm, used mainly for residential ventilation and to study the effect of compression. Four types of ducts, which differ in terms of the shape and material used, were subjected to experimental investigations. Based on the pressure loss measurement, the friction factor f and absolute roughness ε of the flexible ducts in the fully extended state were evaluated. The absolute roughness of the pipe ε varies over a wide range of values (from 0.04 to 2) depending on the material used. It was experimentally confirmed that the plastic ducts behave almost hydraulically smooth in the extended state. The effect of compression on the pressure drop was monitored in two ducts formed by a spirally wound wire. It was found that the pressure drop increases almost linearly with the increasing compression. It is clear from the results that the effect of compression is a major problem for small diameters (80–160 mm). For a compression factor of 15%, the pressure drop of the flexible ducts is 4–8 times higher than in the fully extension state. The key benefit is the knowledge of the pressure loss of flexible air ducts of small diameters depending on the compression ratio.

Characterization of a novel fiber filtration system with a unique mechanism for adjusting the depth of the filter bed

We developed a novel fiber filtration system, which allows the filter bed packing density to be adjusted, to treat raw water of differing turbidities without coagulants. A bench-scale fiber filter is used to remove 5–20 μm poly(methyl methacrylate) particles with high efficiency, without the use of coagulants. The obtained data are analyzed using Yao’s model and regression models. The first filtration cycle achieved a benchmark removal efficiency of 90 % of 5 μm particles for 71 min with a Darcy velocity of 38.2 m/h. Each cycle included a backwash process, but the filtration time gradually decreased to about 46 min by the 5th cycle. However, pressure loss did not increase significantly during the filtration cycles. The shortening duration of filtration over operating successive cycles was postulated as residual particles remaining in the bed after backwash and rinsing. We measured pressure loss at various Darcy velocities for fiber filters with different packing densities and found that the square term of Darcy velocity in Ergun’s model was significant by the regression analysis. Based on the experimental results of the novel fiber filtration system, we compare the performance and running cost of a conventional fiber filtration system and a rapid sand filtration system. The novel fiber filtration system comprising 940 mm fiber filter elements at a packing density of 110 g/L removed 96 % of 5 μm particles at a Darcy velocity about four times greater than that of the rapid sand filter. The running cost of the novel fiber filter was estimated to be approximately one-sixth that of the conventional fiber filter using poly aluminum chloride and less than approximately 30 % of the sand filter.

Comparison of Endwall Loss Reduction Techniques in a High-Lift Turbine Passage

Abstract The development of techniques that reduce the losses in the endwall region is an important area of research as it supports an increase in the turbine design space through the use of higher lift blade designs while maintaining high efficiency. Several active and passive shape contouring methods that reduce losses generated by the secondary flow have been developed and investigated on a high-lift front-loaded low-pressure turbine research profile in a low-speed linear cascade configuration. This paper summarizes and compares alterations to the three-dimensional secondary flow field by the application of three different techniques: blade profile contouring, optimized endwall shape contouring, and localized low mass coefficient jets. Each method was applied to identical research blade profiles and compared in the same linear cascade wind tunnel resulting in a unique perspective into the loss reduction mechanisms associated with each technique. The design strategy will be discussed along with a detailed description of changes to the secondary flow field using in- and out-of-passage total pressure loss measurements and high-speed stereoscopic particle image velocimetry. The key findings include the loss reduction mechanisms associated with each approach and the manipulation of key endwall flow structures such as the passage vortex and a strong suction surface corner separation.

Rheological and flow behavior of water-in-oil Pickering emulsions stabilized with organo-hectorite clay

The rheological and flow behaviors of Pickering emulsions are studied as a function of their water concentration. The studied emulsions are water-in-gasoil inverse emulsions stabilized with organo-hectorite clay. An in-line emulsion preparation was performed and a novel emulsification system was used. The emulsification system was tested and confirmed before performing pipe-flow measurements. A stress-controlled rheometer was used to study the rheological behavior of organoclay stabilized inverse emulsions. It was found that the emulsions exhibited a shear thinning with yield stress non-Newtonian rheological behavior and that the flow curves were well correlated using the Herschel-Bulkley model. Pressure loss and axial velocity measurements were studied to investigate the pipe-flow behavior of the emulsions. Axial velocity of the fluids was measured using an Ultrasonic Pulsed Doppler Velocimeter. It was shown that, up to 50 wt% water mass concentration, an exponential increase of yield stress and viscosity values is noticed, and the phase inversion point is not reached. In the range of the applied flow rates, turbulence took place only in the case of the lowest water cut (0 wt%). The Herschel-Bulkley rheological parameters were used to simulate the pipe-flow behavior of the studied fluids, and showed a satisfactory correlation with the in-line measurements. Furthermore, wall shear stress and velocity profiles were used to study the short-, medium-, and long-term stability of the emulsions.

Rectangle-gap-type laminar flow meter with inward pressure taps

The entrance/exit effects in the current traditional LFMs (Laminar Flow Meter) are unavoidable. LFMs are often designed with a large length-diameter ratio l/d and the consequence is a large pressure loss. A rectangle-gap-type LFM with a laminar flow channel made from the groove between two cubes is proposed and investigated experimentally. The pressure taps located inward the inlet/outlet of the channel replace the original pressure taps that located at the inlet/outlet of channel, so that the rectangle-gap-type LFM can measure the pressure drop from the developed laminar flow to avoid the entrance/exit effects. The results show that the linearity of the rectangle-gap-type LFM is 0.35% for the length-diameter ratio l/dh=93.5. The deviations are −0.35%~+1.30% in the pressure range 100–500 kPa. The estimated pressure loss coefficients (ζent+ζexit) of rectangle-gap-type LFM are only 0.15–0.2, which of traditional LFMs are used to be 1.5. The inward pressure taps allow rectangle-gap-type LFM to adopt a small l/dh design to achieve low pressure loss measurement. The investigation is of positive significance for improving the performance of LFM.

Experimental investigation of the subcooled flow boiling heat transfer of water and nanofluids in a horizontal metal foam tube

The present article experimentally explored heat transfer through a horizontal metal foam tube with a constant wall heat flux during the subcooled flow boiling of water, Al2O3/H2O, and CuO/H2O nanofluids. To investigate the effect of using metallic foam on the subcooled flow boiling heat transfer, the results have been compared with a simple tube. Besides, The impacts of significant parameters, including subcooled inlet temperature (25–60 °C), mass flux (150–310 kg m−2 s−1), wall heat flux (100–230 kW m−2), particle type (CuO and Al2O3), and nanofluids concentration (0.5% wt., 1% wt.) were investigated on the transfer of boiling heat while measuring pressure loss and rate of heat transfer. The results show that the use of metal foam increases the heat transfer rate by 3.5–5.8 times compared to the simple tube. Comparing the subcooled flow boiling heat transfer of water and nanofluids in both metal foam and simple tubes, it was found that water has superiority over the nanofluids. Besides, the value of the thermal performance index defined as a ratio of the heat transfer enhancement to the pressure loss degradation is more than one for water and the nanofluids.

Experimental Study in Measuring Pressure Loss at Micro Channel

The objective of study was to conduct experimental study in measuring the pressure loss due to the major and minor loss in fluid flow at straight and bent micro channel. Test channel had circular cross-sections with hydraulic diameters of 118 µm to 1203 µm for straight and 348 to 1203 for bent micro channels. The results showed that losses for larger diameter of straight channel were well predicted. The bent channel showed that the loss coefficient values were higher if the Reynolds number got smaller.

Online measurement of floc size, viscosity, and consistency of cellulose microfibril suspensions with optical coherence tomography

In this study, cellulose microfibril (CMF) suspensions were imaged during pipe flow at consistencies of 0.4%, 1.0%, and 1.6% with optical coherence tomography (OCT) to obtain images of the structure and the local velocity of the suspension. The viscosities obtained by combining pressure loss measurement with the OCT velocity data showed typical shear thinning behavior and were in excellent agreement with viscosities obtained with ultrasound velocity profiling. The structural OCT images were used to calculate the radial and the axial floc sizes of the suspension. A fit of power law to the geometrical floc size–shear stress data gave the same power law index for all consistencies, suggesting that floc rupture dynamics is independent of consistency. The dependence of viscosity and floc size on shear stress was similar, indicating that the shear thinning behavior of CMF suspensions is closely related to the rupture dynamics of flocs. The results also showed that an apparent attenuation coefficient of the OCT signal can be used to determine the consistency of CMF suspensions.

Measurement of pressure loss throughout a clogged steam generator tube support plate in two-phase flow

Two-phase flow head losses across tube support plates in U-bend tube steam generators are classically evaluated from single phase head losses duly modified with a correction factor to account for two-phase effects.This communication reports upon a series of experiments to feed head loss models for clogged tube support plates under two-phase flow. By using a classical approach, a single phase head loss model is used together with a two-phase flow multiplier. The experiments cover a large span of clogging levels, up to the unrealistic limit case of 95% of clogging.Singular head loss due to the tube support plate is measured under single-phase flow for clean and clogged plates. The head loss factor is hence evaluated and compared to the prediction of some available models. Then the same experiment is repeated under two-phase flow condition. By combining the previously measured single-phase factor with the two-phase flow measurements, recommendations for predicting two-phase flow multiplier with existing models are given.

Experimental and Numerical Study of Heat Transfer and Turbulent Flow Characteristics in Three-Short-Pass Serpentine Cooling Channels With Miniature W-Ribs

Abstract Detailed experimental and numerical studies have been conducted on the heat transfer, pressure loss, and turbulent flow structure of a three-short-pass serpentine cooling channel with miniature W-shaped ribs on the wall under the Reynolds numbers from 8500 to 60,000. Steady-state heat transfer experiments were done to obtain the globally averaged and total heat transfer performance of each ribbed pass of the serpentine channel, and the streamwise pressure loss characteristics of the serpentine-channel flow were also obtained by multipoint pressure measurements. Additionally, the transient liquid crystal thermography technique was also used to obtain the local heat transfer distributions on the miniature W-ribbed surface of each pass. Furthermore, numerical simulations were done by using the AKN k–ε turbulence model to reveal the detailed turbulent flow and heat transfer characteristics in the serpentine channel. The experiments indicate that the miniature W-ribbed short pass has significantly enhanced total heat transfer by a factor of up to 4.0. The total heat transfer enhancement shows appreciably different values in different passes of the serpentine channel, and the second pass shows about 15% higher heat transfer enhancement than the first pass, and the third pass shows the highest heat transfer enhancement, which is about 15% higher than the second pass. The pressure loss measurements indicate that the two flow turnings contribute more than 90% of the total pressure loss in the serpentine channel with one ribbed pass with the miniature W ribs. The numerical simulations indicate that the flow turnings significantly increase the turbulent mixing in the flow of the downstream pass, and the miniature W-ribs on the wall appreciably improve the near-wall vortex mixing, which contributes the heat transfer enhancement.

Subcooled flow boiling of water in a metal-foam tube: An experimental study

The present article experimentally explored heat transfer through a horizontal metal-foam tube with a constant wall heat flux during the subcooled flow boiling of water. The impacts of significant parameters, including subcooled inlet temperature (30–60 °C), mass flux (150–310 kg/m2s), and heat flux (100–230 kW/m2) were investigated on the transfer of boiling heat while measuring pressure loss and heat transfer coefficient. Inserting metal foam into a tube increased the HTC of flow boiling by a maximum of 580%. An increase of 22% was observed in the heat transfer increment divided by pressure loss defined as the thermal performance index.

Turbulent flow in PVC pipes in water distribution systems

ABSTRACT Since the incorporation of PVC as pipe material in the second half of 20th century, its use in the design, rehabilitation and expansion of Water Distribution Networks (WDS) has been widely assimilated. However, materials with higher roughness were more commonly used and with these materials were carried out the studies on which are based the most used design equations (Colebrook-White, Darcy-Weisbach and Hazen-Williams). In this work, the applicability of these equations is tested using PVC as the material to verify their precision. Measurements of pressure loss in different assemblies for extents of Reynolds numbers ranging from 3x104 to 5x105 and relative roughness between 6x10-4 and 2x10-3 were performed. For small diameters, Blasius and Prandtl–von Kármán equations can be used to calculate the friction factor. On the other hand, for larger diameters, the Colebrook-White equation correctly describes the relationship between the friction factor and the Reynolds number.

High frequency pressure loss measurements of laminar-turbulent transitional flow

This paper presents a method for identifying, via pressure measurements at frequencies ranging from 10 Hz–142 Hz, laminar-turbulent transitional flow. The fluctuations in pressure can be successfully used as a diagnostic to infer whether the flow is fully laminar, turbulent or transitioning between the two defined regions. The critical Reynolds number of a flow can be determined from the diagnosis of the pressure loss data at high-frequency when monitored with respect to time. With sufficient resolution of the data, the swift movement between laminar and turbulent flow can be witnessed.

Stress Aortic Valve Index (SAVI) with Dobutamine for Low-Gradient Aortic Stenosis: A Pilot Study

ABSTRACT Background: Potentially some patients have symptoms that arise from their low-gradient aortic valve stenosis (AS). Comprehensive valve physiology with dobutamine stress remains incompletely characterized in this population. Methods: A cohort of 18 subjects with low-gradient AS underwent graded dobutamine infusion with invasive assessment using 0.014” pressure wires. A subset of 4 subjects received thermodilution cardiac output assessment at each stage. Results: Peak dobutamine hemodynamics could not be predicted from clinical or baseline parameters, reflecting statistically the physiologic heterogeneity of the measured pressure loss versus flow curves. While 0 subjects had a baseline aortic/left ventricular pressure ratio during ejection <0.71, 7 of 18 subjects (39%) achieved a ratio during peak dobutamine (the so-called stress aortic valve index, SAVI) below this threshold derived from a prior study of patients undergoing routine transcatheter aortic valve implantation (TAVI). Conclusion: For low-gradient AS, the hemodynamic changes from resting to peak dobutamine conditions cannot be predicted in advance due to pressure loss versus flow curve heterogeneity. A sizable minority of low-gradient AS reaches a severity during dobutamine stress equivalent to patients undergoing TAVI for established benefit. Whether this subset receives similar clinical advantage remains an unproven but natural hypothesis raised by our study.

Experimental and computational aerodynamic characterisation of urban trees

The Darcy–Forchheimer method is used for modelling the airflow through vegetation. Seven tree and shrub species with contrasting leaf morphologies were installed in a wind tunnel to allow pressure loss measurements across the plant section. Aerodynamic parameters derived from this experiment were inserted into a COMSOL Multiphysics computational fluid dynamics model. The model was confirmed to be a good predictor for airflow through vegetation (R2 = 0.98), regardless of plant morphology. Moreover, supplementing these data with results from a previous study (which considered herbaceous species) revealed a pattern of pressure loss data, that was already been normalised for plant area density. Although we propose further research into kinetic energy transfer in vegetation, this study provides sufficient interesting information for further applications and modelling to describe and predict urban ecology.

Frictional pressure losses of Non-Newtonian fluids in helical pipes: Applications for automated rheology measurements

Frequent and accurate drilling fluid measurements are critical to optimum well construction. Proper management of drilling fluid properties such as density and rheology optimizes the fluid's hydraulic and hole cleaning ability while maintaining the fluid in its role as primary well control barrier. In current practice, these measurements are typically done only once or twice a day using the methods described by American Petroleum Institute (API) standards. Moreover, taking the measurements is labor-intensive, and the data quality and reliability are highly dependent on the practicing engineer. An automated, continuous, and practical way of measuring and monitoring drilling fluid properties is therefore needed.In this paper, we introduce a novel helical pipe viscometer system for automated and continuous drilling fluid measurements. A flow-loop was constructed to measure frictional pressure losses of aqueous solutions with various concentrations of xanthan gum in water, generating a non-Newtonian fluid that is best described by a Yield-Power Law (YPL) rheological model. Flow tests were performed simultaneously in two straight- and two helical-pipe test-sections. Flow rate, density, and temperature data were obtained using a Coriolis flow meter. Pressure loss data was obtained using side by side differential pressure measurements from each test-section.A delayed transition to turbulent flow and elevated frictional pressure losses was observed in the experiments with the curved pipes. This is attributed to secondary flow driven by centrifugal forces in the helical pipe system. The results of the experimental data were compiled and used to build an empirical correlation for friction factor predictions using the Dean number. CFD analyses were also performed to validate the accuracy of pressure loss measurements and to obtain a better understanding of the helical velocity profiles. The proposed equation was compared with theoretical equations previously reported in the literature. The results from the analyses show that the equations previously derived for Newtonian and Power Law (PL) fluids are not applicable to YPL fluids in the tested geometries.An algorithm was developed and tested using the experimental data to prove the applicability of the helical system for rheological property calculations. Good accuracy was observed in mud rheology characterization tests. The helical system, which can be fully automated, provides significant practical advantages over standard linear pipe viscometers by offering improved accuracy and smaller footprint. The results of the study are also of importance for the hydraulic design and evaluation of coiled tubing drilling and well completion operations, where the pressure loss is a limiting factor for the maximum flow rate that can be used in such operations.

Rheology and hydraulics of polymer-based foams at elevated temperatures

Foam has been successfully used for different operations like well stimulation, drilling, enhanced oil recovery (EOR), cleanout, and acidizing operations in the oil and gas industry. Additionally, the low liquid content of foam provides a distinct advantage in terms of lesser material requirements. However, accurate prediction of rheology is necessary for the success of field operations, which requires a rheological model that incorporates the effect of temperature on foam properties as it circulates downhole.In the present investigation, polyanionic cellulose (PAC) based foam was generated using nitrogen as the gas phase and its rheology was determined using a recirculating flow loop that has three pipe viscometers (3.05, 6.22, and 12.7 mm ID) and a fully-eccentric annular section (9.53 mm OD × 12.57 mm ID). Experiments were conducted within the temperature range of 24 to 149 °C and at various foam qualities (gas phase volume fraction). The foam was circulated at different flow rates and the differential pressure across each pipe section was recorded. All tests were conducted at 6.89 MPa.The foams displayed power-law fluid behavior in the shear rate range tested (100–5000 s−1), which is often experienced in the wellbore. Like its base liquid, polymer foam exhibited thermal thinning and a significant rheology change with temperature. Only high-quality foam (75%) at ambient temperature (24 °C) showed yielding behavior, which was measured in a pipe viscometer under static condition. The disappearance of yield stress at elevated temperature could be attributed to thermal thinning of the liquid phase that weakens the strength of bubble structure. Experimental data is used to develop new correlations to predict power-law fluid parameters as a function of temperature, base fluid properties, and foam quality. Moreover, the measurements are compared with the predictions of existing models, and discrepancies are observed, which could be attributed to the variation in foam generation technique, the nature and concentration of polymer, and the concentration of surfactant used in the experiments in which data was obtained to develop the models.Furthermore, annular pressure loss measurements obtained at low temperatures (24 and 79 °C) show predominantly good agreement with predictions of a hydraulic model that uses the new correlations. Discrepancies increased with temperature as the foam becomes unstable due to thermal thinning of the liquid film and subsequent weakening of bubble structure.

CLARIFICATION OF AQUEOUS SUSPENSIONS WITH A HIGH CONTENT OF SUSPENDED SOLIDS IN RAPID SAND FILTERS

The presented work is devoted to solving the actual problem of increasing the efficiency of rapid sand filters with granular filling, which operate at a constant filtration rate when cleaning suspensions with a relatively high concentration of contaminants. The proposed mathematical model for clarifying the suspension by filtration consists of three interconnected blocks: clarified, filtration, and hydraulic. Convenient dimensionless mathematical dependencies are obtained for calculating the concentrations of contaminants and sediment from the height of the filter and suspension in the filtrate; head loss in the filter loading; the effective time of the filter (the duration of the filter cycle). The design of the experimental setup and the methodology for conducting experimental studies and mathematical processing of the results are valid. The results of experimental studies of the suspension filtering process through the granular loading are presented, and the obtained data is analyzed. Measurement of pressure losses in the filter loading is performed when a suspension is passed with a relatively high concentration of contaminants at various filtration rates. The nature of the change in the filtration rate with time and height (length) loading at various filtration rates and initial contamination concentrations is determined. Measured variable concentration of suspended matter in filtered water and retained contamination over time. As a result of the experiments, it is confirmed that an increase in the concentration of retained contaminants S leads to an increase in the parameter Δn/n. Upon reaching a certain value of the concentration of the retained sediment S (in our case S=30 g/dm3), an increase in the relative specific volume of the sediment greater than Δn/n0=0.65 is not observed. It is established that an important characteristic of the retained sediment is the ratio of the volume concentration of the sediment to the volume concentration of solid particles in this sediment γ=Csd/Сs. The values of the adhesion and detachment of particles of contaminant in the particles of the material loading =4,9; =0,009. The results of experimental studies in general confirm the correctness and reliability of the obtained analytical dependencies.

Sweeping Jet Film Cooling on a Turbine Vane

The cooling performance of sweeping jet film cooling was studied on a turbine vane suction surface in a low-speed linear cascade wind tunnel. The sweeping jet holes consist of fluidic oscillators with an aspect ratio (AR) of unity and a hole spacing of Pd/D = 6. Infrared (IR) thermography was used to estimate the adiabatic film effectiveness at several blowing ratios and two different freestream turbulence levels (Tu = 0.3% and 6.1%). Convective heat transfer coefficient was measured by a transient IR technique, and the net heat flux benefit was calculated. The total pressure loss due to sweeping jet film cooling was characterized by traversing a total pressure probe at the exit plane of the cascade. Tests were performed with a baseline shaped hole (SH) (777-shaped hole) for comparison. The sweeping jet hole showed higher adiabatic film effectiveness than the 777-shaped hole in the near hole region. Although the unsteady sweeping action of the jet augments heat transfer, the net positive cooling benefit is higher for sweeping jet holes compared to 777 hole at particular flow conditions. The total pressure loss measurement showed a 12% increase in total pressure loss at a blowing ratio of M = 1.5 for sweeping jet hole, while 777-shaped hole showed a 8% total pressure loss increase at the corresponding blowing ratio.