Calculation Of Pressure Drop Research Articles

Progression of left ventricular diastolic function in the neonate and early childhood from transmitral color M-mode filling analysis

We implemented sophisticated color M-mode analysis to assess age-dependent progression of left ventricular (LV) diastolic function. Normal infants were prospectively enrolled for serial echocardiograms at 1 week, 1 month, 6 months, 1 year, and 2 years. From color M-mode scans, propagation velocity (VP), strength of filling (VS), and intraventricular pressure difference (IVPD) in 3 segments along apex-to-mitral valve scan line were measured. Age-wise comparisons of diastolic filling from 121 echocardiograms in 31 infants showed VP (cm/s), VS (cm2/s), and E-wave IVPD (mmHg) at 1 week to be 66.2 ± 11.9, 75.3 ± 19.9, and 1.5 ± 0.4, respectively, while VP, VS, and E-wave IVPD at 1 month were 80.3 ± 14.4, 101.2 ± 28.3, and 2.42 ± 1.1, respectively. There were significant differences in VP and segmental IVPD between first week and first month (p < 0.005) and IVPD between the age groups (p < 0.001). Comprehensive analysis of transmitral color M-mode data is feasible in infants, enabling calculation of pressure drop between the LV base and apex and strength of propagation from two distinct slopes. Profound changes very early followed by relatively constant filling mechanics in later infancy indicate significant LV maturation occurring during the first month of life. We implemented sophisticated analytic methods for color M-mode echocardiography in infants to assess age- and dimension-dependent changes in left ventricular diastolic function. Comprehensive characterization of transmitral color M-mode flow was feasible, enabling calculation of pressure drop between left ventricular base and apex and strength of propagation. Left ventricular diastolic filling function has predictable maturational progression, with significant differences in the intraventricular pressure between infants from birth to 2 years. This study forms the basis for future studies to examine alteration of early diastolic filling in congenital heart disease.

A pore network model for calculating pressure drop in packed beds of arbitrary‐shaped particles

AbstractA pore network model is built to predict pressure drop in packed beds of arbitrary‐shaped particles, using a method that consists of particle packing by the rigid body technique, pore network construction by the maximal sphere algorithm, and numerical calculation of fluid flow. The pore network model is firstly validated by comparing with experiments, Ergun‐type equations, and particle‐resolved computational fluid dynamics (CFD). The pore network model is as accurate as the particle‐resolved CFD, and is remarkably two to three orders of magnitude less computationally intensive. Then, the pore network model is used to calculate the pressure drops in the beds packed with particles of different shapes and sizes, as well as using different flow media. These calculation results prove the versatility of the pore network model. This work provides an accurate yet efficient pore network model for predicting pressure drop, which should be a powerful tool for designing packed beds.

Experimental studies on metallic fuel relocation in a pin bundle core structure of a sodium-cooled fast reactor

Understanding the relocation behavior of metallic fuel in severe accident scenarios is one of the most important factors in the safety assessment of sodium-cooled fast reactors (SFRs). In the present study, the relocation behavior of uranium metallic fuel was investigated by conducting metallic fuel relocation experiments using 19-pin bundle test sections in the Argonne’s Metallic Uranium Safety Experiment (MUSE) facility. Post-test radiographic images were taken to characterize the uranium fuel relocation within the pin bundle test section. In addition, the pressure drop in the test sections was measured after the relocation experiments to evaluate the blockage of the sodium coolant channel. The pressure drop in the pin bundle test sections was also analytically calculated by varying the porosity and the pore size of the relocated fuel. The porosity and pore size of the relocated fuel in the pin bundle test sections were estimated by comparing those calculated pressure drop values with the measured pressure drop values from the pressure drop tests. The experimental results showed that the more formation of the eutectics could lead to more fuel dispersion and less blockage due to the lower freezing point of the eutectics.

Preliminary Design Progress of the CFETR Water-Cooled Divertor

The Chinese Fusion Engineering and Testing Reactor (CFETR) has been performed and is in its engineering design stage. Presently, there are two options allowed for the divertors; the helium-cooled stage and water-cooled stage. The water-cooled one has been focused in this article. The configuration of CFETR divertor module was designed. The cassette design scheme and cassette box inner and outer locking systems were introduced, and the locking system was designed to compliant with the remote-handling (RH) requirements. Two divertor RH design options were provided: one is removed through lower port; the other is targets and baffles removed through upper port; supports and cassette were not removed. The other major research was the water cooling channels’ design and its pressure drop calculation. In addition, the fluid, thermal, and mechanical analyses on the outer target were done. Within 10-MW/m2 heat flux, outer target design can ensure that the temperature for all the components works within their temperature limit, and all the components meet the stress design criteria except the copper alloy pipe. The maximum primary stress induced by pressure on the copper alloy pipe appears in the local position between the two monoblocks, which exceeds the design limit. Protection components are need to be added at the gap of the future design optimization to reduce the local stress. After the thermal-hydraulic analysis on water-cooled divertor cassette, the maximum temperature and the maximum stress of cassette meet the requirements. The results of electromagnetic force analysis shows that the deformation on first wall and transition support is less than 0.5 mm, and the maximum stress is also below its tensile strength values. This article summarized the latest achievements in the design and research of CFETR water-cooled diverter in China. All the results will be of great reference for the CFETR divertor optimal design.

Modeling and validation of carbon dioxide absorption in aqueous solution of piperazine + methyldiethanolamine by PC-SAFT and E-NRTL models in a packed bed pilot plant: Study of kinetics and thermodynamics

A pilot plant with a closed cycle of the absorption/desorption process has been taken into account for the simulation of carbon dioxide (CO2) capture by piperazine (PZ) + methyldiethanolamine (MDEA) solution using Aspen Plus rate-based model with all design and operational parameters such as the hydraulic specifications of absorber and stripper as well as inlet flue gas conditions which are present in a commercial gas-fired burner for heating houses. Metal FLEXIPAC 250Y has been considered as the packing type to apply the model to the proposed correlations on Aspen Plus for calculation of flooding and pressure drop. In order to simulate the process, a new property package has been developed by electrolyte non-random two-liquid (E-NRTL) model and perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state which are used for the calculation of activity and fugacity coefficients respectively. The model has been compared with some experimental data e.g. CO2 absorption efficiency and CO2 loading and demonstrated good agreement with them.

Determining the pressure drop of cemented Gobi sand and tailings paste backfill in a pipe flow

The pressure drop in pipes is a crucial parameter for the design of mine backfill. The friction factor correlations used to predict the pressure drop have not been validated for mine backfill. Therefore, this study presents a flow loop test to estimate the pressure drop based on a practical engineering case of cemented Gobi sand and tailings paste backfill (CGTPB). We employed two friction factor models for the pressure drop calculations in order to compare and validate our proposed test. Moreover, the effects of the CGTPB mixing components (solid mass concentration, binder content, and Gobi sand/tailings ratio) on pressure drop were investigated. Results demonstrate that the Swamee–Aggarwal model is able to effectively predict the pressure drop for Bingham plastic fluids that exhibit a laminar flow within the pipe. Furthermore, the pressure drop increases with concentration and binder content. The gel hydration product provides a lubricating effect that significantly reduces the pressure drop at a greater rate compared to the non-cementitious slurry. In addition, higher combined aggregate packing and slurry bulk densities will increase the pressure drop. The findings from our study contribute strongly to the mine backfill practice.

Effect of baffle cut and baffle spacing on pressure drop in shell and tube heat exchanger with U tubes

A general procedure for heat exchanger design has been presented in the Heat Exchanger Design Handbook (HEDH) [1], but no precise criterion for determining baffle cut nor baffle spacing has been offered, and the emphasis is only on heat exchanger’s permissible range of application. In this paper, an optimization program has been used to calculate pressure drop, fluid velocity, heat power, overall heat transfer coefficient and middle temperature difference for various baffle cut and baffle spacing for the same type of heat exchanger, using the procedure in HEDH. This could be considered as complementary to the HEDH recommendations and can be used by designers and, generally, engineers for determining the right baffle cut and baffle spacing for their specific cases.&#x0D;

Real-Time Estimation and Management of Hydrate Plugging Risk During Deepwater Gas Well Testing

Summary Hydrate formation and deposition are usually encountered during deepwater gas well testing, and if hydrates are not detected and managed in time, a plugging accident can easily occur. In this study, we demonstrate a method for estimating and managing the risk of hydrate plugging in real time during the testing process. The method includes the following steps: predicting the hydrate stability region, calculating the hydrate formation and deposition behaviors, analyzing the effect of the hydrate behaviors on variations in wellhead pressure, monitoring the variations in wellhead pressure and estimating the hydrate plugging risk in real time, and managing the risk in real time. An improved pressure-drop calculation model is established to calculate the pressure drop in annular flows with hydrate behaviors, and it considers the dynamic effect of hydrate behavior on fluid flow and surface roughness. The pressure drops calculated at different times agree well with experimental and field data. A case study is conducted to investigate the applicability of the proposed method, and results show that with the continued formation and deposition of hydrates, both the effective inner diameter of the tubing and the wellhead pressure decrease accordingly. When the wellhead pressure decreases to a critical safety value under a given gas production rate, a hydrate inhibitor must be injected into the tubing to reduce the severity of hydrate plugging. It is also necessary to conduct real-time monitoring of variations in wellhead pressure to guarantee that the risk of hydrate plugging is within a safe range. This method enables the real-time estimation and management of hydrate plugging during the testing process, and it can provide a basis for the safe and efficient testing of deepwater gas wells.

An improved semi-empirical friction model for gas-liquid two-phase flow in horizontal and near horizontal pipes

ABSTRACT Pressure drop and liquid hold-up are two very important fluid flow parameters in design and control of multiphase flow pipelines. Friction factors play an important role in the accurate calculation of pressure drop. Various empirical and semi-empirical closure relations exist in the literature to calculate the liquid-wall, gas-wall and interfacial friction in two-phase pipe flow. However most of them are empirical correlations found under special experimental conditions. In this paper by modification of a friction model available in the literature, an improved semi-empirical model is proposed. The proposed model is incorporated in the two-fluid correlations under equilibrium conditions and solved. Pressure gradient and velocity profiles are validated against experimental data. Using the improved model, the pressure gradient deviation from experiments diminishes by about 3%; the no-slip condition at the interface is satisfied and the velocity profile is predicted in better agreement with the experimental data.

Thixotropy of sweetened condensed milk applied to flow fluid dynamics analysis of cylindrical pipes

AbstractUnderstanding the rheological behavior of fluids and the parameters related to flow fluid dynamics is important for better designing equipment and enhancing processes in the food industry. Thus, the objective of this study was to characterize the rheological behavior of sweetened condensed milk (SCM) in the temperature range of 278.15 to 343.15 K, investigate the friction factor in laminar flow for this fluid, and evaluate the correlation between the rheological behavior obtained from fluid dynamics data and that obtained from rheological assays. The rheological properties of the SCM were determined in triplicate using an AR 2000 controlled tension rotational rheometer with a parallel‐plate and cone‐and‐plate geometry and the pressure drop measurement system consisting of stainless steel pipes connected to a 0.1 m3 stainless steel cylindrical tank. Pseudoplastic behavior with thixotropy was observed, and the friction factor in laminar flow diverged from the theoretical value, with a maximum relative deviation of 42.4% for the data in the descending curve. The maximum relative deviation between the calculated pressure drop and the experimental values was 36.8%. A satisfactory correlation was obtained between the SCM rheological behaviors obtained using rheometer data and pressure drop assays.Practical ApplicationsSweetened condensed milk is one of the main products used in the production of sweets and desserts. Its production involves unity operations, for example, pumping and heat treatments. Correctly designing the equipment used in these operations, as well as enhancing the processing parameters, requires the understanding of fluid rheological behavior, specifically the changes induced when shear rates are applied to the fluid. In the present study, the correlation between the rheology of SCM indicated by fluid dynamics data obtained using a pipe and pumping system and the rheological parameters obtained via rheological tests using a rheometer was investigated to evaluate the behavior of this fluid during its flowing.

Heat transport based on hydrodynamics and the local entropy generation rate in straight and serpentine rectangular packed narrow channels

This work is concerned with the pressure drop (frictional) and local entropy generation rate for the water-toluene, water-benzene, and water-p-xylene (aqueous-organic) two-phase flow through the straight and serpentine rectangular narrow channels, packed with irregularly shaped sand particles of different diameter. The widely used Ergun equation for the calculation of pressure drop in packed bed is modified for the application in randomly packed straight and serpentine narrow rectangular channels in a horizontal orientation. New correlations for the convective heat transfer coefficient are proposed for the flow through the straight and serpentine packed channels. The flow dynamics other than the temperature gradient, on the local entropy generations for the liquid-liquid flows in the packed straight and serpentine channels, are enunciated. The influence of the changing diameter of the packing material and the fluid mixture on the local entropy generation were demonstrated in the present context. The packed straight channel acquires a lower-pressure drop in the absence of Dean flow. The packed serpentine channel of the same dimension, having less entropy generation rate for the same temperature driving force, establishes its efficiency for the more beneficial application to design the heat transport equipment at the higher mass flow rate, provided the same diameter of the packing material and the fluid mixture at the expense of higher pressure drop.

Implication of the Multiphase Influx in Well Control and Circulating System

A multiphase flow system is commonly faced by oil and gas industries where it constituted of complex design and analysis [1]. Previous studies on the multiphase system have established a number of models including Hagerdon &amp; Brown, Duns &amp; Ros, Orkiszewki and Beggs &amp; Brill [1]. Numerous studies have been carried out on the multiphase system related to production engineering [3]. However, the study on the multiphase system is found limited to be related to well control and drilling management. The multiphase system is interestingly important in well control especially during unwanted circumstances such as kick. Flow behavior and pattern might be different from one phase system where normally only gas kick is considered during design stage of the drilling campaign. Since the multiphase kick might represent different outcome compared to one phase system, an accurate calculation of multiphase kick is desired. Therefore, the purpose of this study is to observe the impact on the multiphase kick with on the pressure drop reading and its connection with a circulating system. The study will cover on Pressure drop calculation using Beggs &amp; Brill correlation by consolidating all the data given from various sources; Identification of flow regime of the multiphase system for the base case with several reference pressure; Sensitivity analysis including the effect of different liquid content and liquid flow rate towards the pressure drop. The expected outcomes from this study are beneficial for well control management where necessary actions to prevent blowout.

New Correlations for Two Phase Flow Pressure Drop in Homogeneous Flows Model

The calculation of pressure drop in pipes two-phase flow is essential in different areas. Even though several studies concerning this issue have been conducted, an accurate correlation is still required. The objective of the paper is to develop correlations for two-phase friction pressure drop and mixture viscosity. The new correlation can be used to compute the friction pressure drop for two phase flow in homogenous approach modeling. The original equation is generated from a similitude between the mixture viscosity for two-phase flows and the thermal conductivity of the porous structure. The new correlation is evaluated against 846 experimental data of friction pressure drop collected from literature on circular pipes; the experimental data including different working fluids such as R1234ze (E), R32, R-600a R717, R134a, R410A and carbon dioxide (CO2) at different hydraulic inner diameters and mass flux. Models are assessed based on the relative percentage error and the probability density function (PDF). The predictions by the new correlation and other correlations from the literature are compared based on some experimental data. It is found that new correlation has a mean absolute relative deviation (MARD) of 30%. It is proved that these new correlations of two-phase flow pressure drop can be used to predict the experiment measurements of pressure drop, on circular pipes, minichannels and microchannels.

Validation of Calculated Pressure Drop Using Experimental Data with Standard Methods of an Existing Software

The aim of this research was to determine the pressure drop along a 450 km long multiproduct pipeline. Empirical formulae and quantitative methods were applied in order to establish pressure drop as an operating parameter. Flow rates used were obtained from the daily operation records of two consecutive years and were in the range of 629 – 765 m3/hr. Using four methods, observed pressure drop results when pumping products through the pipeline were as follows: Shell-MIT was 954.5 – 1411.9 bar (gasoline), 1257.6 – 1860.3 bar (kerosene) and 1535.0 – 2270.5 bar (diesel); Benjamin Miller was 0.509 – 0.728 bar/km (gasoline), 0.693 – 0.988 bar/km (kerosene), 0.773 – 1.101 bar/km (diesel); T. R. Aude was 0.590 – 0.841 bar/km (gasoline), 0.814 – 1.161 bar/km (kerosene), 0.907 – 1.294 (diesel); Darcy was 0.578 – 0.857 bar/km (gasoline), 0.703 – 1.042 bar/km (kerosene), 0.858 – 1.272 bar/km (diesel). Simulations using pipe-flow wizard were carried out in order to authenticate the calculated parameters. Results confirmed that Shell-MIT method is only applicable to crude oil pipelines. From comparison of calculated pressure drop, Benjamin Miller’s method was most preferred as it observed the least value within the same flow rate range. Simulation results validated the calculated pressure drop and therefore, calculated Benjamin Miller’s and T. R. Aude’s values are recommended for use in further review study of the said pipeline.

Pressure drop calculation for fly ash slurry using rheological model

Purpose This paper aims to the transportation of high concentration slurry through pipelines that will require thorough understanding of physical and rheological properties of slurry, as well as its hydraulic flow behavior. In spite of several contributions by the previous researchers, there is still a need to enrich the current understanding of hydraulic conveying through pipeline at various flow parameters. The pilot plant loop tests, particularly at high concentrations, are tedious, time-consuming and complex in nature. Therefore, in the current research the prediction methodology for slurry pipeline design based on rheological model of the slurry is used for calculation of pressure drop and other design parameters. Design/methodology/approach It has been established that slurry rheology plays important role in the prediction of pressure drop for laminar and turbulent flow of commercial slurries through pipeline. In the current research fly ash slurry at high concentration is chosen for rheological analysis. The effect of particle size and solid concentration is experimentally tested over the rheological behavior of slurry and based on the rheological data a correlation is developed for calculation of pressure drop in slurry pipeline. Findings The present study strongly supports the analytical approach of pressure drop prediction based on the rheological parameters obtained from the bench scale tests. The rheological properties are strongly influenced by particle size distribution (PSD), shear rate and solid mass concentration of the slurry samples. Pressure drop along the pipeline is highly influenced by flow velocity and solid concentration. The presence of coarser particles in the slurry samples also leads to high pressure drop along the pipeline. As the concentration of solid increase the shear stress and shear viscosity increase cause higher pressure drop. Research limitations/implications The transportation of slurry in the pipeline is very complex as there are lot of factors that affect the flow behavior of slurry in pipelines. From the vast study of literature it is found that flow behavior of slurry changes with the change in parameters such as solids concentration, flow velocity, PSD, chemical additives and so on. Therefore, the accurate prediction of hydraulic parameter is very difficult. Different slurry samples behave differently depending upon their physical and rheological characteristics. So it is required to study each slurry samples individually that is time-consuming and costly. Practical implications Nowadays in the world, long distance slurry pipelines are used for the transportation of highly concentration slurries. Many researchers have carried out an experiment in the design aspects of hydraulic transportation system. Rheological characteristics of slurry also play crucial role in determining important parameters of hydraulic conveying such as head loss in commercial slurry pipeline. The current research is useful for the prediction of pressure drop based on rheological behavior of fly ash slurry at various solid concentrations. The current research is helpful for finding the effect of solid concentration and flow velocity on the flow behavior of slurry. Social implications Slurry pipeline transportation has advantages over rail and road transportation because of low energy consumption, economical, less maintenance and eco-friendly nature. Presently majority of the thermal power plants in India and other parts of the world dispose of coal ash at low concentration (20 per cent by weight) to ash ponds using the slurry pipeline. Transporting solids in slurry pipelines at higher concentrations will require a thorough knowledge of pressure drop. In the current research a rheological model is proposed for prediction of pressure drop in the slurry pipeline, which is useful for optimization of flow parameters. Originality/value All the experimental work is done on fly ash slurry samples collect from the Jharli thermal power plant from Haryana State of India. Bench scale tests are performed in the water resource laboratory of IIT Delhi for physical and rheological analysis of slurry. It has been shown in the results that up to solid concentration of 50 per cent by mass all the samples behave as non-Newtonian and follows a Herschel–Bulkley model with shear thickening behavior. In the present research all the result outcomes are unique and original and does not copied from anywhere.

Flow regime chart for pneumatic conveying

Dense phase pneumatic conveying is preferred by industry over dilute phase flow due to its advantages. Models enabling to calculate pressure drop are worthless for a designer if he is unable to predict in advance the mode of conveying. Therefore, this research is focused on developing a new flow regime chart. Based on hundreds of experiments all required threshold velocities are defined by Reynolds number as a simple power function of Archimedes number. This work, revealed two new kind of plugs unknown before. Using the threshold functions a new flow regime chart was plotted By comparing the results to previously published models characterizing only the material properties revealed that the feeder is probably have a major role controlling the final mode of flow. Taking into account the findings in this paper, one might have ideas of how to improve the feeders in order to fully fulfill the flow potential.

Optimum angles of non-standard diffusers and reducers for engineering application

The fittings such as diffusers and reducers are essential flow elements in a piping system, which play a role to connect the different sized pipes or to branch a part of main stream to other piping. However, their central role is to convert the dynamic energy (velocity) of a flow into the static energy (pressure), or vice versa. When designing a piping system, the pressure drop calculation is very important due to the estimation of power consumption for maintaining a required flowrate. For this reason, many coefficient values of the standard sized fitting products are usually provided by manufacturers or by engineering handbooks. In this study, some analytical calculations were performed to find the optimum angles of non-standard reducers and diffusers based on a dimensionless aspect ratio (length/diameter). The results showed that the optimum angles decreased exponentially as the aspect ratio increased and vice versa. Especially, the optimum angle of a diffuser converged to about 5° when the aspect ratio is over 10. Furthermore, these results were verified through the CFD calculations and the previous reported data.

Handling the pressure drop in strainers

A strainer is a device composed of a perforated plate and mesh element designed to remove debris from fluid. Strainers are used in piping systems to protect sensitive equipment such as pumps and compressors against the dirt and particles carried by the fluid, thereby reducing maintenance and downtime. Strainers are available in different types and are generally considered either permanent or temporary strainers. Different parameters such as installation direction (applicable for conical strainers), strainer type selection, strainer flow open area, basket clogging, and filtration affect the strainers’ pressure drop, as discussed in this paper. Comparing different type of strainers, tee-type and conical-type strainers have higher pressure drop values compared to Y-type and basket-type strainers. Capacity or flow open area of a strainer affects the operation characteristics of the strainer in terms of how long the strainer can operate without cleaning and creating a pressure loss. Clogging the strainer using a finer screen or mesh increases the pressure drop. This paper discusses a model of pressure drop calculation for strainers developed based on the screen opening, viscosity of the fluid, component factor, body factor, etc., using the results from a case study of the pressure drop calculation for a 12″ class 300 strainer in 22Cr duplex material. In addition to discussing clean pressure drop for strainers, this article also reviews an example of pressure drop for a strainer in different cases of clogging (dirty pressure drop).

Two‐Phase Flow Modeling of Direct Methanol Fuel Cell Anode Compartment

AbstractA quasi two‐dimensional numerical model was developed to predict the two‐phase flow behavior within the anode compartment of direct methanol fuel cells (DMFCs). Different void fraction correlations were employed to examine and estimate the pressure drop, flowrate and methanol concentration variations across the fuel channels. By comparing the modeling results with experimental data, it was discovered that the calculated pressure drop values were highly dependent on the type of void fraction correlation utilized. The best experimental agreement was achieved when using the “separated” flow modeling approach with a void fraction correlation that accounted for surface tension and capillary effects. The “homogenous” flow modeling methodology on the other hand, was found to be inadequate and in all cases, underestimated the two‐phase pressure drop. The model demonstrated that the acceleration and gravitational pressure losses had the lowest and highest impact on the overall two‐phase pressure drop, respectively. The frictional pressure loss effects only started to appear at higher fuel flowrates and at elevated operating current densities. It was also revealed that increasing the cell's operating current density while maintaining the fuel flowrate, would significantly increase the overall two‐phase pressure drop with negligible impact on the net methanol concentration across the anode compartment.

Discussion on the pressure drop calculation for oil‐water separated flow using a one dimensional two‐fluid model

The purpose of this work is to seek the key factors influencing the pressure drop calculation for oil‐water separated flow using a one dimensional two‐fluid model. Closure relations published for the two‐fluid model such as interface configuration, wall, and interfacial shear stress correlations are summarized. Interface configurations are established by numerically solving the Young‐Laplace equation, correlated with the Bond number, contact angle, and water holdup. Results show that the interface transforms from concave to convex with the enlargement of the contact angle and becomes flat as the Bond number increases. For the pressure drop calculation, a limited difference of predicted accuracy between the curve and flat interface is found. Discussions of both the wall and interfacial friction factor correlation on the pressure drop calculation are performed. In contrast to the effect of the interfacial friction factor, the correlation of the wall friction factor is found to have more contributions. We validate the prediction accuracy of different wall frictions factors using eight groups of published experiment results, and one correlation is recommended and being further extended.