Two-phase Flow Pressure Drop Research Articles

Pressure Drop in Horizontal Two-Phase Flow

In an artificial environment, the most important key in the process equipment design is determining gas-liquid two-phase flow frictional pressure drop of pipes. To achieve this, an experimental investigation was carried out in this study to analyze the pressure drops of air-water two-phase flow in a 30mm internal diameter horizontal pipe with a length of 6m at different flow conditions. The study was carried out at 20Co using tap water and air. To cover the slug flow pattern, the volumetric flow rate of water varied from 30 to 80 LPM, and the volumetric flow rate of air from 40 to 200 LPM. Pressure transmitters were used to measure pressure at four different points along the test section, each 2m apart. The results of the experiments were compared to 8 models using 3 distinct methods: Mean Absolute Percentage Error (MAPE), Relative Performance Factor (RPF), and the percentage of data included in the range of the 30% error band. All methods produced similar results, with the Sun-Mishima model being the most accurate.

Development of CFD based model for sodium flow boiling in narrow channel akin to SFR fuel subchannel towards high void fraction regimes

The Sodium cooled fast reactor (SFR) is one of the Gen IV reactor type meant for the highest nuclear safety standards. Understanding of flow boiling heat transfer characteristics of liquid sodium is essential under certain postulated events of SFR. This study is intended towards the development of computational fluid dynamics (CFD) based multiphase flow model for the sodium boiling in SFR subchannel using the finite volume method. The numerical simulations have been performed for the basic two-dimensional domain that has a resemblance with the flow subchannel of SFR fuel subassembly. The sodium boiling inception, the nucleate flow boiling regime, and further the forced convective vaporization regime characteristics are numerically predicted by the Eulerian-Eulerian model (two-fluid model) developed using flow regime based modeling within the Algebraic Interfacial Area Density (AIAD) framework for the interfacial closure correlations. The improved non-equilibrium wall boiling model is implemented for wall heat flux partitioning. The liquid turbulence is modeled using a Realizable k-ε model with standard wall function. The CFD simulations are performed for the reference experimental cases of liquid sodium flow boiling in narrow annuli and a tubular channel till high void fraction regimes using the model developed. The predictions of void growth behavior along the axial and in the radial direction depict the dominance of annular flow boiling pattern as observed in sodium flow boiling experiments based on the literature. The numerical predictions for the sodium two-phase flow pressure drop are compared with the experimental results and also with the existing empirical correlations. The mechanistic model-based predictions for boiling heat transfer coefficient are obtained from the wall heat balance model and compared with the available empirical correlations. Also based on the flow parameters predicted the possible flow patterns are identified using the available flow regime maps.

Two-phase flow pressure drop modelling in horizontal pipes with different diameters

The two-phase frictional pressure drop has a dominant effect in many industrial applications associated with the multiphase flow. This study investigated the accuracy of several available methods for predicting two-phase frictional pressure drop of different pipe diameters using 4124 experimental data points. It is observed that the performance of the existing methods is poor in a wide range of operating conditions. Then, several Artificial Neural Network models were proposed, including six multilayer perceptron (MLP) and one Radial Basis Function (RBF) using the same data sets. The weights and biases of the ANNs were optimized using Levenberg-Marquardt (LM), Bayesian Regularization (BR), Scaled Conjugate Gradient (SCG), Resilient Backpropagation (RB), Particle Swarm Optimization (PSO) and Genetic Algorithm (GA). Statistical error analysis indicates that neural network incorporated with the Genetic Algorithm (MLP-GA) predicts the entire data set with a Root Mean Square Error of 0.525 and an Average Absolute Relative Error percentage of 6.722. Finally, the sensitivity analysis was carried out, indicating that the mass flux (G) has the highest direct impact on the two-phase frictional pressure drop.

Experimental Investigation of Two-Phase Flow Boiling Heat Transfer Coefficient and Pressure Drop of R448A inside Multiport Mini-Channel Tube

Regulations and restrictions against high global warming potential (GWP) refrigerants have been introduced to encourage the adoption of environmentally friendly refrigerants and mitigate the environmental impact of the HVAC industry. R448A, a zeotropic blend with a GWP of 1390, has recently been proposed as a drop-in replacement for R404A and R410A in commercial systems. In this study, the heat transfer coefficient and pressure drop characteristics of R448A within a multiport mini-channel tube were experimentally investigated. The experimental ranges of the mass and heat fluxes were 100 to 500 kg/(m2s) and 3–15 kW/m2, respectively. Additionally, the range of quality from 0 to 1 was considered at two fixed saturated temperatures of 3 and 6 °C. The heat transfer coefficient increased with mass flux. Under low mass flux condition, the heat flux increased the heat transfer coefficient, but there was no noticeable effect of the saturated temperature on the heat transfer coefficient. At high mass flux, heat flux had no major effect on heat transfer, while a decrease in the saturated temperature was found to increase the heat transfer coefficient. Moreover, the pressure drop increased with an increase in the mass flux and vapor quality, whereas the heat flux did not affect the pressure drop. The heat transfer coefficient and pressure drop performance of R448A was compared with that of R410A inside the same tube. Finally, correlations for heat transfer coefficient and pressure drop were proposed for the prediction of heat transfer coefficient and pressure drop in practical applications.

Frictional pressure drop of gas-liquid two-phase flow in vertical and inclined upward tubes under heaving oscillation

The study on gas-liquid two-phase flow characteristics of heaving oscillation is of great significance for the safe operation of offshore floating nuclear power platform. In this work, the frictional pressure drop of gas-liquid two-phase flow in vertical and inclined upward tubes under heaving oscillation was studied experimentally. The oscillation frequency was sequentially varied through values of 0.21, 0.42, 0.7 and 0.98 Hz, whereas the oscillation amplitude was 100, 150 and 180 mm. The diameter of the tube was 15, 20 and 25 mm, whereas the inclination angle was 60, 70, 80 and 90°. In total, 579 experimental data points were obtained and used to verify the 24 existing models of frictional pressure drop. The results showed that the existing models had relatively large errors in the calculation of frictional pressure drop under heaving oscillation. Considering the influence of additional force, the calculation method of liquid-phase conversion coefficient was improved, and the new model for the frictional pressure drop in gas-liquid two-phase flow for vertical and inclined upward tubes under heaving oscillation was established. It was found that the model established in this paper can greatly improve the accuracy of frictional pressure drop calculations under heaving oscillation.

Variation Characteristic Analysis of Water Content at the Flow Channel of Proton Exchange Membrane Fuel Cell

The performance of proton exchange membrane fuel cells (PEMFCs) is directly affected by the nonlinear variations in water content. To study the variation in water content and its effect on PEMFC performance, the water condensation rate (WCR) model is established, which determines the proportional relationship between evaporation and condensation rates in terms of the switch function, and the two-phase flow evolution and pressure drop are considered as well. The WCR model is imported into Fluent software through a user-defined function for simulation, and the test system is established under different operating conditions. Then, the contours of H2O molar concentrations and polarization curves are analyzed and compared. The results show that the condensation rate value of the cathode channel is from 1.05 to 1.55 times higher than that of the anode channel. The WCR model can predict the variation in water content and improve the accuracy of the performance calculation by from 9% to 31%. The accuracy of the WCR model is especially improved, by 31%, at high current densities compared with the Fluent model when the inlet pressure is 30 kPa.

Influence of Vertical Downward Annulus Eccentricity on Steam-Water Two-Phase Flow Pressure Drop

Concentric dual-tubing steam injection technique is one of the main methods to improve heavy oil recovery efficiency. From field data, it was discovered that hot fluid at high temperature and pressure caused steam injection casing to have elongation strain and “necking” eccentric buckling, and the eccentricity change affected the accurate prediction of steam-water two-phase flow pressure drop in the steam injection casing. This paper established a coupling model for the steam-water two-phase flow pressure drop in vertical downward eccentric annulus and the wellbore heat transfer and developed a mathematical model calculation program, to validate the accuracy of calculating the liquid holdup and pressure gradient of fully eccentric annulus. This revealed the influential law of eccentricity on the annulus steam-water two-phase pressure, dryness, and enthalpy value. The results indicated that when the eccentricity e increased from 0 to 1, the saturation pressure of steam at annulus wellbore bottom increased by 0.265 MPa, and the dryness and enthalpy value decreased by 8.54 × 10−3 and 11.22 kJ kg−1, respectively. Compared to the concentric layout, the eccentrically arranged steam injection inner tube cannot promote the wet steam dryness at annulus wellbore bottom.

Evaluation analysis of prediction methods for pressure drop of refrigerant-lubricant two-phase flow in compressor suction lines

Evaluation analysis on the approaches for predicting two-phase pressure drop of refrigerant-lubricant oil mixture in compressor suction line is presented in this study. A total of 274 pressure drop data for refrigerant-oil mixture in suction line were adopted to develop a novel consolidated database. These data were collected from the authors’ measurement and four published literatures. The working fluids included R410A, R134a and R32 with their relevant lubricant oils and the database covered the inner diameter, local quality, liquid and vapor Reynolds numbers with the ranges of 7.1–18.5 mm, 0.927–0.994, 0.32–19.1 and 2.59–20.4 × 104, respectively. Two analytical models namely annular flow model (AFM) and double-circle model (DCM) and four representative pressure drop correlations were introduced to conduct an assessment. The comparison result indicated that the analytical models tend to over predict the experimental data of annular flow pattern, while the DCM underestimates the data under stratified-wavy flow conditions. Among the four correlations, Hu correlation provided relatively satisfactory prediction and based on its format, an improved correlation was proposed. The proposed correlation incorporated the surface tension effect and it displayed the best agreement with the database, which yielded mean relative error of 18.16% and captured 85.40% of data within ±30% deviations.

Numerical analysis and artificial neural network-based prediction of two-phase flow pressure drop of refrigerants in T-junction

The two-phase flow behaviors in T-junction are quite complex in energy transport systems. In this paper, the two-phase flow pressure drop of refrigerants in a horizontal branching T-junction was analyzed numerically and predicted using artificial neural network. Firstly, the distribution of static and total pressure was obtained based on Eulerian method, and the parametric studies on the local pressure drop were conducted. It is observed that the vortexes in the entrance of branch pipe lead to the pressure fluctuation and irreversible pressure losses, and the “descend-ascend” of static and total pressure happens under high mass flow split ratio in run pipe. Then, the ANN predicting model of local pressure drop coefficients was established. It shows that GA-BPNN and PSO-BPNN has the best predicting ability for K12J and K13J respectively, and the relative errors are within 10% for most cases. Finally, the sensitivity analysis was conducted, indicating that the effect of mass flow split ratio (F) and inlet quality (x1) is the most significant for K12J and K13J respectively.

Single-Phase and Two-Phase Flow Pressure Drop in a Long Double Helicoidally Coiled Tube

Abstract Single-phase and two-phase frictional pressure drop in horizontally oriented double helically coiled tubes confined in a cylindrical shell are experimentally studied using an instrumented test loop that represents a prototypical liquified natural gas (LNG) fuel delivery system for internal combustion (IC) engines. Adiabatic experimental data addressing liquid (water) and gas (nitrogen) single-phase flows, as well as two-phase flows (air–water) in the helicoidally coiled tubes are presented. The range of Reynold numbers for single-phase flow experiments is 2600–4800. In two-phase flow experiments, the only liquid and only gas Reynolds numbers varied in 1030–6600 and 1700–17700 ranges, respectively. In a laminar single-phase flow regime, the measured friction factors are in relatively good agreement with well-established correlations. In the turbulent flow regime, the measured friction factors are moderately higher than the prediction of well-established published correlations. Two-phase flow frictional pressure drops are compared with some relevant correlations, with the poor agreement. The generated experimental data are empirically correlated based on the two-phase flow multiplier concept.

A computational study of curvature effect on pressure drop of gas-liquid two-phase flow through 90 degree elbow

The CFD analysis of air-water two-phase flows was performed in a 90o vertical to horizontal elbows made of PVC with four different inside diameters (25 mm, 50 mm, 75 mm, and 100 mm) with six different curvature radius to diameter ratios (R/D) 1, 2, 4, 6, 8, and 10. Pressure drops were investigated at various upstream and downstream locations using computational, experimental, empirical methods. The most effective method in investigating and determining total pressure drop of two-phase flow in pipes and bends is considered to be computational study. The CFD simulations were performed using ANSYSY 19.2 FLUENT and a mixture model. The studies were conducted under the following two-phase conditions: mass quality from 1-50% and mass flux from 350-1000 kg/m2s. The results show that the impact of these significant parameters are important and dramatic specially at high curvature radius, mass flux and mass quality. The results of the CFD study demonstrated a substantial loss in energy and pressure as the fluid exits the elbow section, and also a higher drop in pressure observed at higher air velocity. Also, higher pressure drops were obtained with increasing pipe diameter in one side, and with decreasing R/D on the other side. Finally, the current results were verified with the empirical and experimental studies and a good agreement were obtained.

Experimental study on condensation friction pressure drop in rotating channels and proposal of new correlation

The multi-channel cylinder dryer uses the small channels with high heat transfer efficiency to improve the drying efficiency. In practical working conditions, the multi-channel cylinder dryer runs under the rotating state, which would greatly affect the pressure drop of inside two-phase steam. However, the condensation friction pressure drop of two-phase flow in rotating channels has not been well explored. Herein, the condensation pressure drop of two-phase steam in rotating rectangular channels are elaborately studied based on a homemade rotating experiment system. The results show that the friction pressure drop of two-phase flow decreases with the increase of rotation Reynolds number, while increases with the increase of mass flux. Finally, a new correlation of friction pressure drop for two-phase flow condensation in rotating channels is proposed and evaluated by the experimental data.

The Frictional Pressure Drop of Gas-Liquid Two-Phase Flow in Vertical and Inclined Upward Tubes Under Heaving Oscillation

The Frictional Pressure Drop of Gas-Liquid Two-Phase Flow in Vertical and Inclined Upward Tubes Under Heaving Oscillation

Two-Phase Flow Pressure Drop Modelling in Horizontal Pipes with Different Diameters

Two-Phase Flow Pressure Drop Modelling in Horizontal Pipes with Different Diameters

Evaluation of Pressure Drop of Two-Phase Flow Boiling with R290 in Horizontal Mini Channel

Various experiments on the pressure drop of a two-phase flow boiling in a mini channel tube have been carried out. This study is aimed at characteristics of the pressure drop of a two-phase flow boiling using a refrigerant R290. The experiment uses a horizontal, stainless steel, 2-m-long mini-channel tube with a 3-mm inner diameter. The experiment has been carried out using various data with the vapor qualities ranging from 0.1 to 0.9, the mass fluxes ranging 50 kg/m2s to 180 kg/m2s, and the heat fluxes ranging from 5 kW/m2 to 20 kW/m2. Furthermore, several homogeneous and separated methods were used to predict the experimental data. Li and Hibiki’s correlation give the best overall deviation pressure drop value is the most accurate with its deviation amounting 19.47%.

Achieving ultra-high coefficient of performance of two-phase microchannel heat sink with uniform void fraction

Thermal management of high-power electronics/devices has been a very challenging issue for data centers, flourishing electric vehicle revolution as well as cooling of the first wall of a Tokamak fusion reactor. As a prominent cooling strategy, two-phase flow in microchannels has received extensive research over decades. However, inherent defects such as relatively low critical heat flux due to the dry out of liquid film near the exit of the channel and relatively high two-phase flow pressure drop at high heat flux still hinder extensive commercial applications. The present work proposes a robust microchannel heat sink design toward uniform void fraction distribution along the flow direction. The two-phase flow pressure drop will not increase significantly with increase in heat flux. This is made possible by an innovative and unique combination of diverging microchannel and counter-flow manifold, which enables extensive channel-to-channel heat transfer, especially near the end or inlet of the channels. Moreover, flow visualization reveals that nearly uniform void fraction distribution along the channel with relatively high bubble slug ratio is possible. For a relatively large area of 12 cm2 and under the limitation of wall temperature of 140 °C, a heat flux as high as 3525 kW/m2 is achieved without sign of reaching the critical heat flux with nearly negligible pressure drop increment comparing to single-phase convection for a relatively low mass flux of 600 kg/m2s. An ultra-high coefficient of performance of 75,675 is attained under a low inlet temperature and low mass flux.

Experimental investigation on pressure drop characteristics of two-phase flow in a rod bundle geometry under high pressure conditions

In this paper an experimental study on two-phase flow pressure drop characteristics has been performed in a triangular-array rod bundle geometry under various flow conditions (P = 5–9 MPa and G = 100–350 kg·m−2·s−1). Total, gravitational and frictional pressure drops are obtained by measurement methods. The effects of pressure, mass flux and thermodynamic quality on pressure drop were investigated in detail, and the proportions of gravitational and frictional pressure drop in total pressure drop are analyzed. Meanwhile, an assessment of eight existing correlations for two-phase friction multiplier calculation is carried out against the present data. The results show that Tran correlation has a relatively better performance when predicting the present data, while the accuracy is still not good enough. In views of this, a newly-developed correlation based on the Tran correlation has been proposed for the two-phase friction multiplier calculation in rod bundle geometries, which is proved to agree with the present data well.

Local Measurements in Heat Exchangers: A Systematic Review and Regression Analysis

It is widely known that most of the heat transfer and pressure drop measurements in heat exchangers are global measurements that are based on surface averaged parameters that do not measure the growth of the hydraulic and thermal boundary layer. Recent local heat transfer coefficient investigations on hydrocarbon condensation in plate heat exchangers suggest that the mean heat transfer coefficients obtained from local measurements are 10–20% higher than those obtained from studies based on a uniform wall heat flux assumption. Consequently, process heat exchangers which were rated by global measurements could be underrated. This systematic review presents a meta-analysis and regression analysis of the available pressure drop and heat transfer data for both single-phase and two-phase flows in enhanced heat exchangers. Data was compiled from studies in the last decade for similar Reynolds, Prandtl, Dean, Weber, and boiling numbers, pitch/diameter ratio, and other parameter ratios for statistical analysis and correlation development. State-of-the-art local measurement techniques like liquid crystal thermography are also discussed. Both practicing engineers and graduate students should benefit from this study.

FLOW PATTERN, PRESSURE DROP, AND VOID FRACTUION IN VERTICAL TWO COMPONENT TWO-PHASE PIPE FLOW

Two-phase flow pattern, pressure drop, and void fraction in vertical transparent pipe of x m internal diameter and y m length is investigated experimentally. The rig is designed to achieve the measurements of pressure drop and void fraction for different combinations of phase superficial velocities such that the regimes encountered are bubbly, slug and annular, which required a wide range of water and air superficial velocities.

Characterization of the Pressure Drop during Condensation in Channels of Multi-Channel Cylinder Dryer Using Homogeneous and Separated Flow Models

The condensation resistance characteristics of steam flow in horizontal rectangular channels of multi-channel cylinder dryer (MCD) is a very important factor that affects the heat transfer, while it is not very clear due to the limited studies. In this paper, the frictional resistance characteristics of the two-phase flow (steam and water) in the rectangular small channels of MCD were investigated with deionized water as the working fluid, and the calculation models, homogeneous and separated flow models, of the two-phase flow pressure drop in the channel were verified and evaluated. It showed that the main part of the total pressure drop was the frictional pressure drop, which means that the calculation of frictional pressure drop was the key to the calculation of the pressure drop of the two-phase flow in the channel. Meanwhile, it was found that the homogeneous model was not suitable for the calculation of the frictional pressure drop and the separated flow model was completely in line with the experimental data. In this study, the converted coefficient of complete steam/liquid phase were concerned to calculate the frictional resistance using five separated flow models. It was found that the Chisholm B model showed better accuracy than prior correlations, which was greatly consistent with experimental data, and the average absolute percentage deviation (MAPE) was 24.9%.