Calculation Of Pressure Losses Research Articles

Probabilistic optimal design concerning uncertainties and on-site adaptive commissioning of air-conditioning water pump systems in buildings

Sizing of air-conditioning water pump systems in buildings is a critical issue in design practice concerning the pump energy consumption in operation and risk of being undersized. As a result, significant energy is often wasted in operation due to oversizing to avoid the risk of being undersized. In current practice, throttling of commissioning valves are commonly adopted to push water flowrate (and pressure head) back to the design point no matter how much oversizing exists in a system. That partly mitigates the oversizing problem. This paper presents a novel approach consisting of probabilistic optimal design concerning uncertainties and on-site adaptive commissioning to further maximize energy savings of constant water flow pump systems. Minimized throttling is achieved by on-site adaptive commissioning, which reduces unnecessary pressure head and significant energy consumption. Pumps selected by the probabilistic optimal design can operate under both conventional design conditions and the projected possible off-design (oversized) conditions. The projection is based on the probability distribution of actual pressure head, which is estimated using Monte Carlo simulation by quantifying uncertainties in pressure loss calculation and system construction. Three case studies are conducted to test and validate this new design and commissioning approach. Results show that about 20% energy saving could be achieved, when the system is oversized by 20%, compared to conventional design and commissioning methods. The proposed approach also offers better energy performance in general compared to the designs all using variable speed pumps.

Study on Hydraulic Transport of Large Solid Particles in Inclined Pipes for Subsea Mining

For subsea mining, the prediction of pressure loss due to the hydraulic transport of solid particles in the flexible pipe to connect the mining tool and the lifting system is important for the design of mining system. The configuration of the flexible pipe is expected to have an inclined part. In the present paper, the authors developed a mathematical model to predict the pressure loss in inclined pipes. The total pressure loss is expressed by the summation of the loss due to a liquid single-phase flow and the additional loss due to the existence of solid particles. The additional pressure loss can be divided into the variation in static pressure due to the existence of solid particles, the loss due to the particle-to-pipe wall friction and collisions, and the loss due to the particle-to-particle collisions. The empirical formula in horizontal pipes proposed by the other researchers was applied to the model of the last two losses. Furthermore, we carried out the experiment on hydraulic transport of solid particles in a pipe. In the experiment, alumina beads, glass beads, and gravel were used as the solid particles, and the inclination angles of the pipe were varied to investigate the effect of the pipe inclination on the pressure loss. The calculated pressure loss using the model was compared with the experimental data. As the results of the comparison, it was confirmed that the developed model could be applied to the prediction of the pressure loss in inclined pipes.

Thermal-hydraulic comparisons of 19-pin rod bundles with four circular and trapezoid shaped wire wraps

Coolant in wire-wrapped fuel assembly flows not only in axial direction but also in a transverse direction. This special flow is critical for momentum exchange and heat transfer in fuel rod bundle. To obtain a better performance wire-wrapped fuel assembly for advanced reactor cores, in this paper, the characteristics of turbulent flow and heat transfer inside 19-pin heated rod bundles where each pin is wrapped with four circular shaped and four trapezoid shaped wires are numerically studied, respectively. Considering the geometric complexity, the advanced hybrid-grid technique that combines the structured hexahedron grids and unstructured pentahedral grids is adopted to divide the modeling assembly. The validity of both RSM and SST k-ω model is assessed by comparing calculated pressure loss with the available experimental data to determine a proper turbulence closure. Special attention has been paid to understand the effect of secondary flows created by the wire wraps on the reduction of coolant temperature variation. Additionally, in order to assess the effectiveness of the different shaped wires, comparisons on both global heat transfer and associated penalty in pressure loss are evaluated. Results indicate that the frictional pressure loss of the rod bundle with circular shaped wires is smaller than that with trapezoid shaped wires, while the global heat transfer is equivalent. However, the trapezoid shaped wires give a lower maximum temperature as well as a uniform temperature distribution within the subassembly in comparison with circular shaped geometry.

Optimization of Crossflow Staggered Tube Banks for Prescribed Pressure Loss and Effectiveness

For many applications, it is important to transfer a given amount of heat with minimum possible volume of heat exchanger for a given pressure loss and effectiveness. In this study, optimum design of crossflow staggered tube banks for prescribed pressure loss and effectiveness is carried out. For this purpose, the method of Gnielinski–Gaddis is used for the calculation of heat transfer coefficient and pressure loss in tube banks. By prescribing the tube diameter, heat exchanger effectiveness, and pressure loss of the heat exchanger, the pitch length and tube number in the flow direction are determined for the condition of the maximum heat flow per heat exchanger volume. For a given value of total heat to be transferred, the length, height, and width of the heat exchanger can be determined by the equations that are derived using appropriate dimensionless numbers.

Modeling of inertial multi-phase flows through high permeability porous media: Friction closure laws

During a severe accident in a nuclear reactor, the core may be fragmented in a debris bed made of millimetric particles. The main safety procedure consists in injecting water into the core leading to a steam-water flow through a hot porous medium. To assess the coolability of debris bed, there is a need for an accurate two-phase flow model including closure laws for the pressure drop. In this article, a new model for calculating pressure losses in two-phase, incompressible, Newtonian fluid flows through homogeneous porous media is proposed. It has been obtained following recent developments in theoretical averaging of momentum equations in porous media. The pressure drops in the momentum equations are determined by eight terms corresponding to the viscous and inertial friction in liquid and gas phases, and interfacial friction between the phases. Analytical correlations with the void fraction have been formulated for each term using an original experimental database containing measurements of pressure drops, average velocities and void fractions from the IRSN CALIDE experiment. The new model has then been validated against the experimental data for various liquid and gas Reynolds numbers up to several hundreds. Finally, it has been compared to the models, usually used in the “severe accident” codes, which are based on a generalization of the Ergun law for multi-phase flows. The results show that the new model gives a better prediction both for the pressure drop and for the void fraction.

Condensation inside smooth horizontal tubes: Part 2. Improvement of heat exchange prediction

In this study, a theoretical model of film condensation inside horizontal tubes with more precise definition of friction coefficient on interphase is presented to calculate the heat transfer coefficient under two-phase annular and intermediate flow conditions. This more precise definition contains experimental substantiation of correction for calculation of pressure losses by friction and correction that takes into account surface suction on the interphase. Comparison of this model with the experimental data of various authors demonstrates that the results are in satisfactory and close agreement.

The properties of concrete mixes, pumped over long distances

The influence of technological factors, chemical and mineral admixtures on pumping and thixotropic properties of concrete mixtures was studied. The causes of the loss of pressure when pumping concrete mixtures through channels of a complex section are established. Existing methods for calculating pressure loss during pumping of concrete mixtures are considered. Some results of pumping tests of modern concrete mixtures are given. It is shown that the use of powdered concrete with high mobility for pumping over long distances during the filling of long-span metal or bridge structures, concreting in tunnels where injection pressure is limited, can be the only solution in the implementation of these tasks.

Hydraulic Design of the Bleeding Chamber for the Steam Turbine

Hydraulic Design of the Bleeding Chamber for the Steam Turbine Hydraulic loss coefficients in the turbine flow discharge section were calculated on the basis of experimental determination of pressure losses in the turbine section designed for the heating bleeding in the steam turbine. It has been established that these loss coefficients are affected by the number of outlet branches, the diameters of outlet branches, a value of throat cross-section (narrow), radial cone cross-section through which the steam enters the bleeding section, and a relative flow of effluent medium (up to 35 %). The investigation was carried out using the aerodynamic test bench. The bleeding chamber was designed with the axial symmetry and had a large volume peculiar for the turbines with large uncontrolled steam bleedings. Consideration was given to the operation of the options of bleeding channels that have radial cone elements and also the options that have no radial cone. The technique was given that allows us to calculate pressure losses in the region between the flow passage of real steam turbine and the bleeding branches. This technique was developed based on the experimental investigation of bleeding channel carried out using the stationary aerodynamic test bench. It has been established that the use of two outlet branches instead of one results in a more substantial decrease of losses in the diffuser bleeding channel in comparison with the approach when the area of one outlet branch is increased two times.

Application of general regression neural network (GRNN) for indirect measuring pressure loss of Herschel–Bulkley drilling fluids in oil drilling

Experimental measurements of the pressure losses in a well annulus are costly and time consuming. Pressure loss calculations in annulus is generally conducted based on an extension of empirical correlations developed for Newtonian fluids and extending pipe flow correlations. However, correct estimation of pressure loss of non-Newtonian fluids in oil well drilling operations is very important for optimum design of piping system and minimizing the power consumption. In this paper, a general regression neural network (GRNN) was applied to predict the pressure loss of Herschel–Bulkley drilling fluids in concentric and eccentric annulus. Experimental data from literature were used to train the GRNN for estimating pressure losses in annulus. The predicted values using GRNN closely followed the experimental ones with an average relative absolute error less than 6.24%, and correlation coefficient (R) of 0.99 for pressure loss estimation.

Consideration of Tool-Joint Effects for Annular Pressure Loss Calculation

Consideration of Tool-Joint Effects for Annular Pressure Loss Calculation

Optimum Design of Cross-Flow In-Line Tube Banks at Constant Wall Temperature

For many applications, it is important to transfer a given amount of heat with minimum possible volume of heat exchanger for a given pressure loss and efficiency. In this study, such optimum design of cross-flow in-line tube banks at constant wall temperature is carried out. For this purpose, two different methods, namely, the Gnielinski + Gaddis and Zukauskas methods, for the calculation of heat transfer coefficient and pressure loss in tube banks are used. By prescribing the tube diameter, heat exchanger efficiency, and pressure loss of heat exchanger, the pitch length and tube numbers in the flow direction are determined for the condition of the maximum heat flow per heat exchanger volume. For a given value of total heat to be transferred, the length, the height, and the width of heat exchanger can be determined. Equations for this optimum design are derived using appropriate dimensionless numbers. The methodology of the optimum design is explained for a practical example.

SOME TECHNICAL ASPECTS OF THE RHEOLOGICAL PROPERTIES OF HIGH CONCENTRATION FINE SUSPENSIONS TO AVOID ENVIRONMENTAL DISASTERS

The behavior of slurries and suspensions made by mixing solid particles and liquids is very important for various industrial applications. The latest accidental failure events at tailings facilities (Kolontár, Baia Mare) have focused public interest into this field. Nowadays, environmental practice is turning to use dry deposition techniques or at least as high concentration slurries or pastes as possible, to avoid large spills in case of an accidental failure of an embankment. High concentration slurries are becoming widely accepted in many environmentally related operations such as underground backfilling or simple tailings deposition. However, the hydraulic transport of pastes or high density slurries requires higher energy input via pumps, and, in addition, the energy requirement or pressure loss calculation methods are also different because the rheology of pastes differs from that of dilute slurries. At the University of Miskolc, Institute of Raw Materials Preparation and Environmental Processing, Miskolc, Hungary, this topic has been studied for many decades. The fine suspension – coarse mixture flow model was introduced, and it has been determined that the flow behavior of fine suspensions made of solid particles smaller than a limit particle size can be measured and interpreted in almost the same way as for single phase clear liquids. Based on these measured rheological parameters of fine suspensions, the frictional energy loss can be calculated. The aim of this paper is to give a summary and data base about the rheological behavior of different industrial materials based on pilot scale hydraulic loop measurements. An Anton-Paar rotational viscometer and a tube viscometer with three measuring pipe sections,– developed by our institute – were used for testing. The results of measurements of various granular materials, such as sands, fly ashes, perlite, tailings and red mud are presented in connection with environmental applications. Based on these results, empirical relationships are presented, where the parameters are determined by simple function fitting into the data of measurements carried out at discrete concentration values. The rheology of fine suspensions of any concentration up to the measured maximum can be calculated by these relationships.

Frictional Pressure Losses of Fluids Flowing in Circular Conduits: A Review

Summary Fluids are pumped through circular conduits in various operations in the petroleum industry. These fluids may be Newtonian or non-Newtonian, clean or proppant-laden, polymer-based or surfactant-based, single-phase or multiphase, drag-reducing, and others. They are pumped through straight and coiled tubing under laminar- or turbulent-flow conditions. Calculation of frictional pressure losses for these circumstances is crucial for the success of the operation. A simple Darcy-Weisbach (Darcy 1857) equation is widely used to calculate frictional pressure losses in pipes. However, a unique term, friction factor, has to be determined. Enormous numbers of correlations are available to determine the friction factor. These correlations vary in complexity and applicability and have their own positive and negative features. In addition, several parameters included in the correlations have to be identified, and they vary from one correlation to another. The task at hand is determining the proper correlation. Estimating the friction factor is not an easy task, and it can be very confusing. Inaccurate estimation may lead to erroneous results and failure of operations. This study provides a comprehensive review of the friction-factor correlations and presents how to select the most-suitable correlation for specific conditions. It discusses the parameters involved in friction-factor calculation and how to define them. The authors compare and question the applicability, accuracy, and limitations of each correlation to propose the most-accurate ones. An innovative, user-friendly, and step-by-step code using the most widely used and accurate correlations can then be developed to predict the friction factor. The present study is an effort to simplify the friction-factor challenge. It aims at providing the most-accurate friction-factor correlations to overcome the complexity faced when calculating frictional pressure losses. In conclusion, it summarizes the state of the art in the field of fluids and hydraulics in the oil and gas industry.

Optimising shaft pressure losses through computational fluid dynamic modelling

In recent years, substantial progress has been made with respect to the definition and control of the primary energy requirements in underground mines. Little has, however been done to develop a more detailed understanding of how to limit the various pressure losses which are intrinsic to shaft systems. This is in spite of the fact that more than half of the pressures generated by the ventilation fans in deep level mines are dissipated as pressure losses within the shaft system.This paper presents research which has been completed to optimize the pressure losses which occur in shaft systems as a result of the ventilation air flowing through them. In this regard, the response of various shafts to the ventilation air flowing through them was measured. These results were evaluated against the current theory for the calculation of shaft pressure losses. Finally the results of the measurements and calculations were used to calibrate a Computational Fluid Dynamics model of the shaft systems. This model was then iterated to allow meaningful conclusions as to the specific make up of the shaft equipment which contributes the most to pressure losses in shaft.The results of the above analysis demonstrated that the current theory used for the evaluation of these pressure losses is deficient. The paper discusses these conclusions and the specific ramifications of the analysis.Finally, the understandings gained with regards to the above research are applied to the design and layout of equipment in mine shafts. In this regard, the shape and orientation of the shaft steelwork is evaluated and its specific interaction with the piping and fitting is evaluated. Coming out of this evaluation are specific recommendations for the design of future shaft systems. These recommendations are based on the above models and offer specific savings on the lifetime operating costs of shaft systems.

A unified method for estimating pressure losses at vascular junctions.

In reduced-order (0D/1D) blood or respiratory flow models, pressure losses at junctions are usually neglected. However, these may become important where velocities are high and significant flow redirection occurs. Current methods for estimating losses rely on relatively complex empirical equations that are only valid for specific junction geometries and flow regimes. In pulsatile multi-directional flows, switching between empirical equations upon reversing flow may introduce unrealistic discontinuities in simulated haemodynamic waveforms. Drawing from work by Bassett et al. (SAE Trans 112:565-583, 2003), we therefore developed a unified method (Unified0D) for estimating loss coefficients that can be applied to any junction (i.e. any number of branches at any angle) and any flow regime. Discontinuities in simulated waveforms were avoided by extending Bassett et al.'s control volume-based method to incorporate a 'pseudodatum' supplier branch, an imaginary effective vessel containing all inflow to the junction. Energy exchange between diverging flow streams was also accounted for empirically. The formulation was validated using high resolution computational fluid dynamics in a wide range flow conditions and junction configurations. In a pulsatile 1D simulation exhibiting transitions between four different flow regimes, the new formulation produced smooth transitions in calculated pressure losses.

Thermo-economic analysis of combined power and water production in Iran by multi effect desalination method

Current study reports thermo-economic evaluation of various configurations of combined electricity and potable water production systems. All of these systems use single pressure heat recovery steam generators and multi-effect seawater desalination systems coupled to single cycle gas turbine power plants. These combined power and water production plants are located in the south of Iran near salt water of the Persian Gulf. The aim of this work is to find the most appropriate combination of gas turbines with different capacities (4, 10, 25 MW) to produce 18,000 m3/d fresh water. In this regard, a complete model of the system, including thermodynamics, heat transfer, and economic models as well as pressure loss calculations are developed. In this model, steady state mass and energy conservation equations are considered for each component of every configuration as a control volume. The results from this thermo-economic analysis of whole cycle are reported as the levelized cost of electricity, desalination water cost, and internal rate of return for investment. The capital, operation, and fuel costs were assumed due to available data for these specific systems and market of Iran.

LDA Study of Particulate Flow in a Channel with Deformed Surface Locations and with Flow Conditioner

Hydroabrasion in particulate flows plays an important role in various industrial and natural processes. To predict the effects of particulate flow and the resulting phenomena such as erosion/abrasion in a pipeline, channel or a fitting, it is essential to characterize the effects in a simple standardized geometry. For this purpose, it is vital to initially understand the particulate flow behavior and motion in such geometries. In the present work, two series of experimental works by application of the LDA measurement technique were successfully conducted. First, the particulate flow behavior at downstream of a flow conditioner inside a channel with square cross-section was investigated. Shorter lengths for fully development of velocity profile by using the self-constructed flow conditioner were observed. Moreover, the flow at downstream of the conditioner was modeled with the CFD tool (ANSYS-CFX V. 14.57) and the simulation results were compared and validated by the LDA experimental data. Better agreement between the simulation results and experimental data was observed in the fully developed region. However, there are some deviations due to the actual pressure loss through the experimental loop and the calculated pressure loss value, which includes some assumptions for the loss coefficients. Furthermore, the particulate flow behavior and vortex generation inside the deformed locations of a channel surface were studied in detail. With the help of the Matlab program, it was possible to calculate and visualize the velocity vectors for each measured point inside the channel accurately.

Pressure drop estimation in horizontal annuli for liquid–gas 2 phase flow: Comparison of mechanistic models and computational intelligence techniques

Frictional pressure loss calculations and estimating the performance of cuttings transport during underbalanced drilling operations are more difficult due to the characteristics of multi-phase fluid flow inside the wellbore. In directional or horizontal wellbores, such calculations are becoming more complicated due to the inclined wellbore sections, since gravitational force components are required to be considered properly. Even though there are numerous studies performed on pressure drop estimation for multiphase flow in inclined pipes, not as many studies have been conducted for multiphase flow in annular geometries with eccentricity. In this study, the frictional pressure losses are examined thoroughly for liquid–gas multiphase flow in horizontal eccentric annulus.Pressure drop measurements for different liquid and gas flow rates are recorded. Using the experimental data, a mechanistic model based on the modification of Lockhart and Martinelli [18] is developed. Additionally, 4 different computational intelligence techniques (nearest neighbor, regression trees, multilayer perceptron and Support Vector Machines – SVM) are modeled and developed for pressure drop estimation.The results indicate that both mechanistic model and computational intelligence techniques estimated the frictional pressure losses successfully for the given flow conditions, when compared with the experimental results. It is also noted that the computational intelligence techniques performed slightly better than the mechanistic model.

Diagrams for Analysis of Film Units

Diagrams are proposed for determination of film-flow regimes of water along pipe walls, and for calculation of film thickness and pressure losses during ascent of a parallel-current flow. The question concerning the driving force for absorption in parallel- and counter-current flow regimes is examined.

A generalized hydraulic calculation model for non-newtonian fluid pipe flow and its application evaluation

A generalized hydraulic model that is independent of the rheological model is presented for non-Newtonian fluids flow in pipes. The generalized model was developed without assuming that the generalized flow index (n’) remains constant over all shear rates. Based on the pipe flow control equation, the explicit equations between the wall shear stress and volumetric flow of all common rheological models flowing in pipe were obtained, such as the Casson model, HerschelBulkley model and the Robertson-Stiff model, and they all can be solved numerically to obtain the accurate wall shear rate and shear stress. We give the theoretic calculation method of n’ for all time-independent non-Newtonian fluids. This method is applicable to all common rheological models without the assumption that n’ is constant. Moreover, we derived the general expression of generalized Reynolds number and then gave a utility pressure loss calculation model. A set of measured hydraulic data were utilized to evaluate this model. The results show that it can precisely calculate pipe flow parameters for all types of different non-Newtonian fluid. The proposed model will lay a foundation for the application and more extensive use of complex but more precise rheological models in engineering.