Flow Pressure Loss Research Articles

Performance and flow characteristics of the liquid turbine for supercritical compressed air energy storage system

• Geometrical models of liquid turbines affect the accuracy of predicted efficiency. • The model with a nozzle and a rotor predictes the efficiency with 15.8% error. • The total pressure loss of the rotor accounts for the largest portion among all parts. • The nonuniform flow in the nozzle and the rotor is significant at low flow rates. The liquid turbine can replace throttling valves during the depressurization process of high-pressure liquid or supercritical fluid and improve the system efficiency of many industrial systems. However, there is no research about studying the internal flow and total pressure loss of liquid turbines, which can affect the turbine performance significantly. In this paper, performance and flow characteristics in a liquid turbine were analyzed for supercritical compressed air energy storage (SC-CAES) systems in the first time. Three typical topology models (C1, C2 and C3) of the tested liquid turbine were simulated and their performances were compared with experimental results. The deviation of the turbine efficiency between C3 and the experiment was less than 2%, while C1 had a constant increment of the turbine efficiency about 15.8% with the experiment. The total pressure loss in each part was evaluated and the flow characteristics in the nozzle and the rotor were analyzed. Nonuniform flow affected the nozzle’s total pressure loss significantly, while the rotor’s total pressure loss was related to the development of low energy regions. The results obtained in this paper provides guidance for optimizing liquid turbines and improving the turbine performance for various industrial systems with throttling valves installed.

Mechanism Analysis of Falling Film Evaporation Two-Phase Flow in Narrow Channels

Abstract As an efficient heat and mass transfer technology, falling film evaporation has attracted more and more scholars' attention. In this paper, a falling film evaporation platform was established to discuss the mechanism of two-phase flow in narrow channels. The width of the channel varied from 0.5 to 2.0 mm. We focused on the relationship between heat transfer characteristics with flow patterns, channel width, and pressure loss. Three kinds of flow patterns were observed: bubble flow, restricted bubble flow, and dry area. In channels with the same width, the initial heat flux of subcooled evaporation increased linearly with the growth of flow rate. But at the same flow rate, the initial heat flux of subcooled evaporation decreased when the channel width became larger. The heat transfer coefficient on the wall was influenced by the bubble generation frequency and bubble separation diameter. Higher bubble generation frequency led to smaller bubble separation diameter. Through mathematical analysis, it was found that the heat transfer coefficient changed with the channel size. And a boundary was observed between the strengthening and weakening status. The comparison of theoretical and experimental values showed good agreement.

Numerical study on influence of water based hybrid nanofluid and porous media on heat transfer and pressure loss

The performance augmentation of the heat exchangers is a deal between heat transfer improvement and pressure loss penalty. There is no study investigating this deal as the thermal performance index of the heat exchangers filled by hybrid nanofluid and porous media. The thermophysical properties of TiO2–Al2O3/water are available in the literature, but no study is dedicated to evaluating the flow characteristics of such a hybrid nanofluid, especially in a porous material. This paper is intended to explore the heat transfer and pressure loss of a turbulent convective flow of hybrid nanofluid (TiO2–Al2O3/water) and porous media in a double-pipe heat exchanger with a counter flow. Hot water flows in an annular pipe to warm cold nanofluid flow in an inner pipe. The effect of two porous media is examined for inserting in the inner pipe. Hybrid nanofluid increases the heat transfer (maximum 6%) and pressure loss (maximum 11%). The thermal performance index of the hybrid nanofluid in the aluminum porous media is less than 0.6, while this for the copper media is more than 1. Correlations for the calculations of the Nusselt number and friction factor of the turbulent hybrid nanofluid flow in porous media are missing in the literature. So, for the first time, equations were proposed for finding the Nusselt number and friction factor of the hybrid nanofluid in both empty and porous pipes.

On the flow of liquid crystals through 90° bends

During the processing of nematic soft solids through process flow elements (pipe bends, elbows, etc.), the constitutive behavior makes its presence felt via processing (with rheology driven effects increasing pressure drop) and the final product microstructure. This paper explores the flow and microstructure configurations of nematic liquid crystals in a pressure driven flow through 90° pipe bends with different types of wall anchoring. The governing equations of the Leslie–Ericksen theory are solved numerically in a newly developed OpenFOAM solver. We show that the bend curvature deforms the nematic axis distribution; the distortion can be driven either by elastic or hydrodynamic effects. The interaction between the nematic microstructure and flow field generates non-zero normal stresses (in the radial, azimuthal, and streamwise directions), which produce a secondary flow and increase pressure losses. The strength of the secondary flow depends on the type of wall anchoring and Ericksen number; in configurations with homeotropic anchoring, decreasing the Ericksen number increases the relative strength of the secondary flow (with respect to the mean flow velocity). Conversely, homogeneous (planar) anchoring reduces normal stresses, thus weakening the secondary flow strength. We show that as the fluid enters/leaves the bend, there is a perturbation in the transverse velocity caused by streamwise stress gradients. The perturbation magnitude depends on material properties and can be of different values at the bend exit and entrance. Finally, we show that the spatial development of the nematic field downstream of the bend exit is controlled by both material properties and the Ericksen number.

Experimental Study of Pressure Losses in a Two-Phase Flow in Vertical Pipes

Experimental Study of Pressure Losses in a Two-Phase Flow in Vertical Pipes

Effects of varied bend turning vanes on flow control and heat transfer performance in a smooth two-pass channel

Turbine blades are always withstanding high temperature and thermal stress from hot gas. Serpentine passages with 180-deg turns are widely used within the turbine blade so as to guide cooling flow and enhance heat transfer. However, there is always a large pressure drop when cooling airflow passes the 180-deg bend. Turning vanes are usually arranged in the bend of two-pass channel to reduce the flow separation and pressure loss, and improve mainstream uniformity in the second passage. In this study, the heat transfer performance and flow field features of six two-pass channels with / without varied turning vanes are investigated by using Computational Fluid Dynamics numerical methods. The studies on effects of shape lines and curvature of the turning vane are conducted by commercial software Fluent based on realizable k - ε turbulent model. The influences of Reynolds number are also included. Numerical results indicate that the friction loss factors of channels with turning vane are decreased by 10.5%–31.4% compared to smooth channel without turning vane. However, the Nusselt number in the second passage is reduced greatly by 12.6%–22.1%. Considering the heat transfer and pressure loss, semicircular turning vane yields the highest thermal performance factor with an improvement by 5.2%. Moreover, turning vane with big curvature shows the best ability to suppress the flow separation and recirculation around the divider in the second passage. Among all the turning vanes studied, the novel airfoil-shaped turning vane produces the highest transfer augmentation at the region downstream the bend.

Methodology to Remediate and Evaluate Surface Flowline Capacity with Coiled Tubing Cleanouts

Summary Customers in Ecuador inject the byproduct formation water from production wells into injector wells. A limited injection rate bottlenecks production, which is economically undesirable. Two major contributors limit injection capacity: reservoir injectivity and flowline pressure losses. In the latter case, paraffins, asphaltenes, and scale, collectively referred to as “schmoo,” progressively build in the flowline and reduce the internal diameter (ID), limiting flow rate capacity. One cost-effective method to remediate flowlines with significant deposits is coiled tubing (CT) cleanouts. This unconventional method, which calls for optimized planning, execution, and performance evaluation, has been implemented in five flowlines. An economic analysis shows that remediating flowlines using CT cleanout yields significant savings as compared with replacement. After a candidate is identified, job planning takes into consideration flowline length and deviation (to identify maximum reach of CT), schmoo analysis (to design an optimal bottomhole assembly and fluid treatment), and execution logistics (to ensure a viable, reliable, and safe operation). After the cleanout, the flowline is put back into service, and the effectiveness of the treatment is estimated based on system flow rates and pressure losses. The equivalent ID for the flowlines was improved by more than 49% in each of the remediated flowlines, achieving an effectiveness of more than 89% of nominal ID and increasing flow rates without a detrimental effect on system pressure. The cleanouts reestablished nominal capacity in more than 50,000 ft of flowline that no longer needed replacement. Lessons learned include the ability to complete the cleanout with water alone. The chemical analysis in planning stages showed the absence of carbonates, which enabled a mechanical cleanout with a high-pressure nozzle. Nonetheless, a chemical treatment was designed as a contingency. Another learning was that though tubing force models helped predict the reach of the CT, other factors created limitations. For example, the weld bead on the flowline limited the reach of the CT and required reevaluating where to create cuts along the flowline. Finally, deploying the CT in a flowline required configuring the injector head horizontally, which required a customized base for safe rig-up and operation of the injector head and pressure-control equipment (PCE). CT successfully cleaned out five flowlines with IDs ranging from 6 to 8 in. and reestablished 89 to 98% of their nominal ID. As a result, the operator saved upward of USD 14 million in flowline replacement costs, increased asset usage, and decreased deferred injection. Historically, there is limited documented experience with flowline cleanouts using CT. The paper documents a repeatable methodology for candidate selection, planning, execution, and performance evaluation. It also provides basic building blocks to meet treatment design, rig-up, and execution requirements that are unique to this application.

Mathematical description of the grain cleaning process on the experimental facility

Machines with pneumatic systems are used to clean grain from light impurities and dust. Modern grain cleaning machines for preliminary cleaning from light impurities and dust with a pneumatic system do not fully meet the increasing requirements of modern agricultural production in terms of their performance. The article presents the principle of operation and a mathematical description that allows you to determine the main parameters of the installation. In this work, an analytical research method was used based on the analysis of differential equations describing the processes of cleaning grain from light impurities and dust. To develop a mathematical model, the method of constructing Lagrange mathematical models was applied. On the basis of this model, a number of equations were constructed that characterize: the transition of the potential energy of the grain mass into the kinetic energy of the grain flow; dynamic equation of the equilibrium fall of the grain flow; the volume flow rate of the air flow in the intergranular space, as well as an equation that makes it possible to determine the pressure loss in the air flow passing through the blinds and the average speed of the grains falling. Taking into account the above equations, a mathematical model is built in the form of a system of equations. This mathematical model makes it possible to determine the main design parameters of the new installation: the geometric dimensions of the working area, as well as energy costs for the grain cleaning process. The introduction of the developed installation at the receiving points of the elevators makes it possible to increase the efficiency of grain cleaning from light impurities and dust at low unit costs.

Friction factor estimation for turbulent flow of Herschel-Bulkley and power law fluids in pipes

Determining the appropriate friction factor value for calculating the frictional pressure loss of non-Newtonian fluids in a pipe is a critical task. This study aims to obtain an explicit friction factor correlation to accurately calculate the pressure losses for turbulent flow of yield pseudoplastic fluids in both smooth and rough pipes. A series of experiments are carried out with carboxymethyl cellulose (CMC) solutions using pipes of three different relative roughness. The Herschel-Bulkley model is found to be the most appropriate model to describe the yield pseudoplastic behavior of the CMC solutions used in this study. Based on the experimental friction pressure data obtained from the Izmir Katip Çelebi University flow loop, an explicit correlation is developed here. The new friction factor equation is compared with not only experiments in this study, but also experimental data presented by Okafor and Evers (1992), Subramanian (1995) and Vjargah et al. (2017). Results show that the proposed friction factor correlation is more consistent and better in agreement with experimental data than existing correlations in the literature. • This is the first study to experimentally investigate the turbulent flow of yield-pseudoplastic fluids in rough pipes. • A new explicit friction factor correlation for determining the pressure losses of non-Newtonian fluids accurately in rough and smooth pipes is proposed. • Experiments are carried out with various CMC solutions using pipes of three different relative roughness. • The Herschel-Bulkley model are found to be the most appropriate model to describe the yield pseudoplastic behavior of the CMC solutions. • The proposed friction factor correlation is more consistent and better in agreement with experimental data than existing correlations in the literature.

Experimental study of turbulent flow heat transfer and pressure loss over surfaces with dense micro-depth dimples under viscous sublayer

Presented are experimentally-measured heat transfer and pressure loss characteristics for dimpled surfaces, placed along one surface of a channel, with different ratios of dimple depth to channel height δ/H, and for Reynolds numbers ranging from 10,000 to 70,000. With the same relative dimple spacing to dimple print diameter, and the same ratio of dimple depth to dimple print diameter of δ/d = 0.20, experimental results for arrays of spherical indentation dimples with micro depths of δ = 0.6 and 1.0 mm (δ/H = 0.03 and 0.05) are compared with thermal characteristics for arrays of larger dimples with δ = 4.0 mm and δ/H = 0.20. Local surface heat transfer distributions are measured using transient liquid crystal thermography. Additional steady-state experiments are also employed to provide overall heat transfer enhancement and friction factor augmentation values. Results indicate that Nusselt number ratios and friction factor ratios of a turbulent flow in the channel are dependent upon the ratio of dimple micro depth to channel height, which are different findings from previous studies with larger-depth dimples in the cooling channels. As such, the present data for micro-depth dimples with ratios of dimple depth to channel height δ/H of 0.03 and 0.05 are firstly provided. The importance of a critical Reynolds number is demonstrated by the results, which is determined when the ratio of viscous sublayer layer thickness to the dimple depth is equal to unity, and has been ignored in the previous dimpled channel heat transfer design. Nusselt number enhancements for the micro dimples are generally lower at lower Reynolds numbers, but increase as the Reynolds number becomes larger and approaches the critical Reynolds number. Nusselt number enhancements are then approximately invariant with Reynolds number, when Reynolds number then exceeds the critical value.

Laminar flow and pressure drop of complex fluids in a Sulzer SMX+TM static mixer

Static mixers are an effective model system for investigating the effect of fluid rheology on pressure losses in laminar flow. Viscoelastic pressure drop enhancement in real process fluids was investigated using experimental methods and computer simulations of a SMX+TM mixer. The results were compared against classical friction factor correlations for non-elastic fluids and literature correlation for elastic fluids (developed using aqueous polymers). CFD predictions of pressure losses for both inelastic and viscoelastic process fluids were consistent with the measurements. The literature correlation for viscoelastic fluids progressively overestimated the friction factor with increasing Reynolds number. The CFD results were analysed to discern the impact of the flow field on laminar mixing.

ESTIMATE RIG CAPACITY AND RENTAL COST IN DRILLING OPERATION GH-02 WELL EXPLORATION MATALOKO GEOTHERMAL FIELDRATION GH-02 WELL EXPLORATION MATALOKO GEOTHERMAL FIELD

Exploration well GH-02 will be drilled directionally at an inclination of 44º and a target of 5920 ft MD or 4840 ft TVD. So that the drilling process can be safe, the rig capacity must be determined optimally so that it is not over capacity which causes higher rig rental costs and also low capacity which causes disruption of the drilling process. The main components that influence the calculation of the horsepower required by the rig are the hoisting system, the rotary system, and the circulation system. The amount of horsepower required in the hoisting system is influenced by the lifting velocity, the hook load and the efficiency factor. While the rotary system is influenced by the amount of rpm and the target depth. Circulation system is influenced by the pump flow rate and pressure loss along the circulation system. The total horsepower required can be calculated by adding up the horsepower from the hoisting system, rotary system, circulation system, plus the safety factor of 100-250 HP for rigs with more than 1000 horsepower. The drilling time is designed optimally so that not much time is wasted which can cause the drilling costs to increase expensive. The amount of the rig rental cost is obtained from the rig rental cost per day with the planned drilling time. The results of the case study calculations show that the rig capacity is 1500 horsepower, drilling is carried out for 22 days and the cost of renting the rig is 660000 USD

CFD modeling of turbulent flow for Non-Newtonian fluids in rough pipes

Non-Newtonian fluids are pumped under laminar and turbulent regimes through pipes in numerous industries. Proper calculation of pressure losses is essential to optimize available horsepower. In actual practice, no pipe surface is smooth. Pipe roughness has significant influence on the pressure loss for turbulent flow. In this study, a mechanistic model is developed to predict pressure losses of Herschel-Bulkley and Power-Law fluids in rough pipes for the turbulent flow regime. A numerical scheme is applied to the proposed model to obtain an approximate solution. The proposed model is separated into two sub-problems in order to obtain a numerical solution. One is solved analytically for the viscous sublayer, which is determined by pipe roughness and the other is solved numerically by the virtue of the central difference approximation along with the frozen non-linear term for the turbulent core region. Moreover, an experimental study is conducted using two different high viscous polymer base fluids with two different concentrations and three different rough pipe diameters. The mechanistic model results are compared with experimental data in this study and presented by Subramanian (1995). Absolute Average Percent Error (AAPE) of 13.3% is calculated for the proposed model compared to experimental measurements.

Dynamics and friction losses of the flow of yield-stress fluids through 90° pipe bends

We characterise the dynamics and the pressure losses of yield-stress fluid flow through 90° pipe bends using Computational Fluid Dynamics. We show that the bend can influence the flow far upstream and downstream depending on the Bingham number – the ratio of the yield-stress to viscous stresses – even under conditions where fluid inertia can be considered negligible. Moreover, non-Newtonian viscous effects counteract centrifugal forces and suppress secondary motion. We also show that the Darcy–Weisbach equation with a generalised version of the Reynolds number can accurately predict pressure losses. This applies to a wide range of bend curvatures and rheological parameters, and elastoviscoplastic fluids with Saramito-type rheology and elastic moduli as small as 500 Pa. Our model holds for multiple adjacent bends, with minimal impact from interactions between bends. Deviations from this model occur when inertial effects in the flow become significant and are smaller for yield stress fluids than Newtonian fluids.

Multi-objective optimization of multi-stage heat sink of electric aircraft using three-dimensional thermal network analysis

The efficiency, reliability, and safety of aircraft have been improved by substituting hydraulic and mechanical systems with electric systems. Furthermore, in future electric aircraft, where fan-driving engines are partially replaced by electric motors, solving the thermal management of heat generation from the motor-controlling power-devices will become a crucial problem. In this study, three-dimensional steady thermal network analysis (TNA) was carried out to analyze the temperature field in a heat sink, for motor-controller air cooling, which is expected to be used for the future electric aircraft. The numerical procedure used was verified by comparing the results of TNA with those of three-dimensional fluid-solid conjugate heat transfer analysis using finite volume method. After the verification, TNA was carried out for an aircraft flight scenario, where the optimum geometry of the heat sink was investigated, minimizing the following three objective functions: the pressure loss of air flow through the heat sink, the maximum local wall temperature of the heat sink at the surface of motor controller, and the weight of the heat sink. In this multi-objective optimization, the design of experiments technique was used to decide the space-filling points for the six design parameters. The three objective functions at each sampling point were calculated using TNA. A response surface was created for each objective function. A multi-objective optimization on the response surfaces, using a genetic algorithm, was iteratively carried out to find the Pareto optimal solutions for the air-cooled multi-stage heat sink. From the results of the Pareto optimal solutions, the effects of the design parameters on the objective functions were discussed. In addition, multiple regression analysis was performed for quantitative evaluation of the results of the Pareto optimal solutions, and the dominant design parameters for each objective function were identified.

Experimental study of pressure losses in non-equilibrium two-phase flow

Experimental study of pressure losses in non-equilibrium two-phase flow

Wake characteristics of a steam turbine rotor tip linear cascade blade in subsonic flow

Experimental investigations have been carried out on a steam turbine rotor tip linear cascade to determine the effect of Mach number on the flow and total pressure losses at zero degree of incidence. Static pressure distribution on the blade surfaces have been measured. Exit flow survey has been carried out using a precalibrated five hole probe at the corresponding Mach number. The exit Mach number has been varied from 0.27 to 0.52. The effect of Mach number on various parameters such as lift coefficient, total pressure loss coefficient, mass averaged exit flow parameters and wake parameters has been found to be small. Wake self-similarity has been observed for velocity profiles at all Mach numbers. The wake half widths and integral thicknesses increase slowly with Mach number. Shape factors are in the range of 1.1 to 1.4, indicating turbulent boundary layers on the suction and pressure surfaces of the blade.

ABOUT SELECTING THE VORTEX FLOWMETER OPTIMAL BLUFF BODY SHAPE

Vortex flow meters are becoming more widespread in many industries. This is due to the simplicity and reliability of the flow transducer, the scale linearity, the frequency measuring signal presence, low requirements for alignment and ensuring the straight sections length at the installation site, etc. Among the vortex measuring instruments, the most common are instruments with a bluff body. Such flow meters operation principle is based on measuring the vortex stripping frequency behind a streamlined body installed in the flow.
 In this case, the metrological characteristics are determined by the bluff body shape. Therefore, the search for the optimal sensing element shape and the hydraulic channel configuration of the flow meter as a whole remains an actual issue.
 The paper proposes an algorithm for solving this issue according to the criteria of the measured flow rates maximum range and the interaction efficiency of the bluff body with the measured medium flow. The first criterion value is determined from the condition that the Strouhal’s number remains unchanged; the second criterion is based on the estimation of the measured medium pressure drop and the measurement error.
 To realize the algorithm, simulation modeling is used in the Ansys Fluent fluid simulation software, which uses computational fluid dynamics methods. Modeling carried out for three shapes of the bluff body: a cylinder, a prism with a triangular section, a prism with a trapezoidal section, which made it possible to choose a sensitive element for further solving the multi-parameter optimization problem.
 Geometric features of the selected sensitive element shape, the limits of their change and boundary values are grounded.
 The simulation made it possible to estimate the measured flow rates range and pressure losses, as well as to determine the vortex stripping frequency, measurement error and efficiency factor for the investigated geometric model.
 To further improve the instrument metrological parameters, the authors proposed to supplement the primary transducer geometric model with gradual contraction and diffuser sections. These sections parameters are selected from the conditions of a continuous flow and the maximum measured flow rates range with a minimum pressure loss.
 The obtained results confirmed the strategy proposed by the authors. The further research prospect is to carry out simulation studies of the flow meter hydraulic channel proposed configuration for different measured media.

NUMERICAL MODELLING OF OSCILLATING FLOW FOR ENERGY HARVESTING

The energy efficiency of systems, equipment, and sensors is nowadays intensively studied. The new generation of microelectronic sensors is very sophisticated and the energy consumption is in the microwatts range. The energy to power the microelectronic devices can be harvested from oscillating flow in small size channels and so replaceable batteries could be eliminated. Piezoelectric elements can convert energy from oscillation to electrical energy. This paper focuses on the simulation of periodic flow in the fluidic oscillator. CFD simulations were performed for several values of the flow rate. Experimental measurement was carried out under the same conditions as the CFD experiment. The main monitored and evaluated parameters were volume flow rate and pressure loss. Fluid oscillations were analysed based on CFD simulations and the theoretical maximum energy available for the deformation of piezoelectric elements and transformable into electrical energy was evaluated.

Numerical study of heat transfer and flow structure over channel surfaces featuring miniature V rib-dimples with various configurations

In order to enhance the heat transfer performance of the internal cooling for gas turbine blades, miniature V rib-dimple hybrid structures on cooling channel surfaces were studied numerically at Re = 50,500, and the effects of parameters of rib heights, dimple depths, rib pitches and rib-to-dimple pitches were detailly investigated on the turbulent flow structure, pressure loss and heat transfer characteristics. The Abe Kondoh Nagano (AKN) k−ε turbulence model was utilized for the numerical simulation work. The results showed that as the rib height and dimple depth increase, the globally averaged heat transfer augmentation increases significantly at first, and then becomes stable. And the maximum heat transfer enhancement is reached when the rib height-to-channel hydraulic diameter ratio is 0.075 and the dimple depth-to-diameter ratio is 0.2. Besides, the more densely fabricated hybrid structures induce higher heat transfer, while a relatively larger spacing between the rib and the downstream dimple also obtains higher heat transfer. Within the parameters of this study, the total heat transfer enhancement of the hybrid structures can be up to 95.3% and 43.2% respectively higher than that of the dimple-only and the rib-only structures. The optimal hybrid structure with the overall thermal performance factor of 1.73, with e/Dh=0.075, δ/d = 0.2, P1/e = 7.2 and L/P1 = 0.83, has a total Nusselt number ratio of 3.9 and a friction ratio of 11.6. It is evident that with the miniature V rib-dimple hybrid structure, the turbulent kinetic energy of the flow passing over the V ribs is enhanced, thereby reducing the recirculation zone in the front of the dimples. Additionally, the vortex flow induced by the V rib strongly interacts with the downstream dimpled wall which significantly augments the overall momentum and heat transport of the near-wall flow field, and contributes to enhanced and more uniformly distributed heat transfer on the channel surface.