Two-phase Pressure Drop Data Research Articles

Study on Two-Phase Pressure Drop of Methane during Flow Boiling in Mini Channel

For LOX/LCH4 variable thrust rocket engine, the propellant methane is traditionally selected as the coolant in regenerative cooling channel (RCC). With the decrease of engine thrust, the mass flow rate of coolant methane decreases gradually. At low engine thrust, the coolant methane is usually in a subcritical state. The heat transfer deterioration of subcritical methane occurs in RCC, which may cause thrust chamber wall ablation. The two-phase pressure drop data of methane are crucial parameters for the design and optimization of RCC. But it is rarely to find such measured frictional pressure drop data of methane in open published literature. The two-phase pressure drop of methane during flow boiling in the single mini channels with the diameters of 2.0 mm are investigated systematically. Effects of the mass flux (582.19~1755.48 kg/m2·s), inlet pressure (0.56~3.55 MPa), heat flux (53.25~318.68 kW/m2) on the frictional pressure drop of methane are discussed. The results show that the frictional pressure drop of methane during flow boiling increases with mass flux and inlet pressure at the experimental conditions, and heat flux shows weak effect on the frictional pressure drop. The comparisons of the experimental data with the predicted value by existing six correlations are analyzed. Contrary to the conventional channels, homogeneous model yields better prediction than five separated flow models. Present experimental results can provide reference for the design and optimization of RCC in LOX/LCH4 rocket engine.

Thermal-hydraulic characterization of R513A during flow boiling inside a 6.0 mm horizontal tube, comparison with R134a and development of a new correlation

This paper presents two-phase heat transfer coefficient and pressure drop data of refrigerant R513A, a new azeotropic mixture conceived as possible alternative to R134a for medium temperature small-size refrigeration systems. All the experiments were performed in a commercial horizontal stainless-steel tube having an internal diameter of 6.0 mm and an outer diameter of 8.0 mm. The channel heating was obtained through DC current and Joule effect. The effect of the main operating parameters in terms of mass flux (from 150 to 500 kg/m2s), heat flux (from 5.0 to 40 kW/m2), saturation temperature (from 30 to 50 °C) and vapor quality (from the onset of boiling up to the dry-out occurrence) was analyzed and discussed for the heat transfer coefficient values, finding that both convective and nucleate boiling were significant contributions. The same ranges of mass flux and saturation temperature were also applied to frictional pressure gradient trends with vapor quality, taken in adiabatic conditions. The thermo-hydraulic performances were then compared with those of R134a, obtaining lower heat transfer coefficients and very similar pressure gradients. Finally, the collected experiments were assessed with values predicted from the most quoted correlations available in literature. A new composite method for nucleate-dominant or convective-dominant mechanisms was proposed for the evaluation of the heat transfer coefficient, with a mean absolute error of 25.3%, whereas the frictional pressure gradient values were well predicted with the Friedel correlation, that provides a mean absolute error of 13.8%.

Experimental Investigation on Adiabatic Two-Phase Frictional Pressure Drop of R1234ze(E) and R134a in a Horizontal Minichannel

Abstract R1234ze(E) has been created as an environmentally friendly substitution of R134a. An experimental investigation on adiabatic two-phase frictional pressure drop inside a 1.88 mm horizontal minichannel with R1234ze(E) and R134a was conducted. The saturation pressure and mass flux ranged within 0.6–0.9 MPa and 450–900 kg/(m2 s). Based on the 299 measured data points, the influences of various factors, including saturation pressure, mass flux, and the like, are examined detailedly. Larger mass flux brings about larger frictional pressure drop, and vapor quality performs the same function, but saturation pressure works inversely. The frictional pressure drops between R1234ze(E) and R134a present no significant differences. The experimental data are compared against 23 predictive models, among which the one from Xu and Fang (2013, “A New Correlation of Two-Phase Frictional Pressure Drop for Condensing Flow in Pipes,” Nucl. Eng. Des., 263, pp. 87–96) gives the best accuracy. In addition, a database including 3150 experimental adiabatic two-phase frictional pressure drop data points is derived from the current study and 29 published literature. Based on the database, the 23 models are assessed, and the most effective one is from Müller-Steinhagen and Heck (1986, “A Simple Friction Pressure Drop Correlation for Two-Phase Flow in Pipes,” Chem. Eng. Process., 20(6), pp. 297–308). This work can provide guidance for choosing appropriate two-phase frictional pressure drop models under adiabatic conditions.

Experimental Investigation and Prediction on Pressure Drop during Flow Boiling in Horizontal Microchannels.

In this paper, two-phase pressure drop data were obtained for boiling in horizontal rectangular microchannels with a hydraulic diameter of 0.55 mm for R-134a over mass velocities from 790 to 1122 kg/(m2·s), heat fluxes from 0 to 31.08 kW/m2 and vapor qualities from 0 to 0.25. The experimental results show that the Chisholm parameter in the separated flow model relies heavily on the vapor quality, especially in the low vapor quality region (from 0 to 0.1), where the two-phase flow pattern is mainly bubbly and slug flow. Then, the measured pressure drop data are compared with those from six separated flow models. Based on the comparison result, the superficial gas flux jg is introduced in this paper to consider the comprehensive influence of mass velocity and vapor quality on two-phase flow pressure drop, and a new equation for the Chisholm parameter in the separated flow model is proposed as a function of the superficial gas flux jg. The mean absolute error (MAE) of the new flow correlation is 16.82%, which is significantly lower than the other correlations. Moreover, the applicability of the new expression has been verified by the experimental data in other literatures.

Experimental investigation and correlation development for two-phase pressure drop characteristics of flow boiling in offset strip fin channels

The plate-fin heat exchangers with pressure-resistant offset strip fins are widely used in the C3MR and other liquid natural gas (LNG) systems, and the two-phase pressure drop characteristics of flow boiling in pressure-resistant offset strip fin channels is a crucial factor for designing and optimizing the compact heat exchangers. A cryogenic experimental rig was established to obtain two-phase pressure drop data in the present study and the fin thickness of 0.4 mm is selected based on an actual compact heat exchanger in the C3MR LNG liquefaction system. The tested fluid is R22, and the experimental conditions include mass fluxes of 64–128 kg/(m2·s), vapor qualities of 0.1–1.0, saturation pressures of 0.22–0.26 MPa, and heat fluxes of 0.7–5.5 kW/m2. The comparison between the obtained data for fin thickness of 0.4 mm and those for fin thickness of 0.1–0.4 mm in literatures show that, the friction factor f of gas flow in channels increases with the increasing fin thickness, and the increment is 306%–451% as the fin thickness increases from 0.1 mm to 0.4 mm. The research results of two-phase flow show that, as the vapor quality increases, the frictional pressure drops initially increase and then decrease, representing a maximum at vapor quality of 0.90. With the increment of heat fluxes, the average vapor quality increases, resulting in the increasing frictional pressure drops. The two-phase multiplier of two-phase pressure drop varies from 3 to 35 and increases with the decreasing fin thickness and hydraulic diameter. A new correlation of two-phase pressure drops in offset strip fins with different fin thicknesses was developed within a deviation of ±25%.

Condensation of ternary low GWP zeotropic mixtures inside channels

The condensation heat transfer coefficient and two-phase frictional pressure drop of ternary zeotropic mixtures R455A (R32, R1234yf and R744 at 21.5/75.5/3.0% by mass composition) and R452B (R32, R1234yf and R125 at 67.0/26.0/7.0% by mass composition) have been measured inside a minichannel (0.96 mm diameter) and a conventional tube (8.0 mm diameter). The effects of tube diameter, mass velocity, vapor quality and saturation-to-wall temperature difference have been investigated. A comparison between the experimental data of the tested mixtures and the condensation heat transfer of the pure components R32 and R1234yf has been performed. The two-phase pressure drop and condensation heat transfer data are compared to predictions of correlations available in the literature. In the prediction of the heat transfer coefficient, the models are adapted to account for the additional mass transfer resistance occurring during condensation of zeotropic mixtures.

Research on pressure drop characteristics in inverted half U-tube bundle under two-phase cross-flow condition

An experimental research has been carried out for vertically upward two-phase flow of air-water across inverted half U-tube bundle with or without anti-vibration bars. Pressure drop characteristics in inverted half U-tube bundle and anti-vibration bars were obtained and analyzed. New correlations for total pressure drop of two-phase flow in inverted half U-tube bundle and local pressure drop of two-phase flow in anti-vibration bars were developed. The measured two-phase pressure drops in inverted half U-tube bundle of three walls in the test sections were unequal. The pressure drop in the side wall dominated the total pressure drop of two-phase flow in inverted half U-tube bundle for 57 ≤ G < 114 kg·m−2·s−1, while the pressure drop in the front wall dominated for 114 < G ≤ 143 kg·m−2·s−1. An obvious mass velocity effect was observed for the total pressure drop of two-phase flow in inverted half U-tube bundle. For a given Martinelli parameter, the total pressure drop of two-phase flow in inverted half U-tube bundle decreased with an increasing mass velocity. The two-phase local pressure drop data of anti-vibration bars could be fitted well in terms of the Martinelli parameter and mass velocity.

Behavior and pressure drop of an upwardly two-phase flow through multi-hole orifices

Experimental results on hydrodynamic behavior and pressure drop of two-phase mixture flowing upwardly in a pipe containing single- and/or multi-hole orifice plate are presented. It was found from the measurement of the void fraction upstream and downstream the orifices that the flow behavior is significantly affected by the layout of the orifice plate used and the flow starts to recover after approximately 7 D downstream the orifice. Furthermore, increasing orifice holes number results in decreasing the slip ratio. The standard deviation of the void fraction was used to identify the flow pattern before and after the orifices and found that the critical threshold transition occurred at a standard deviation of 0.2. The flow homogenization necessitates a minimum value of the liquid superficial velocity to occur, and the position where it takes place depends on this velocity and on the orifice holes number. It was also inferred from the two-phase pressure drop data across the orifices that three different flow regimes, where the transition between bubbly-to-slug and slug-to-churn flow, can be identified. An assessment of the predicted two-phase flow multiplier using some previous models dedicated to single-hole orifice was achieved; and found that the model proposed by Simpson et al. is the most reliable one. Single-phase pressure drop was also measured and compared with correlations from literature.

Detailed experimental investigations on frictional pressure drop of R134a during flow boiling in 5 mm diameter channel: The influence of acceleration pressure drop component

This article presents detailed two-phase diabatic pressure drop data for refrigerant R134a at a saturation pressure of 5.5 bar corresponding to the saturation temperature of 19.4 °C. Study cases have been set for a mass flux varying from 100 to 500 kg m−2 s−1.The obtained data are used as a validation of the void fraction literature models, a set of graphs shows comparisons, for a representative set of experimental conditions, of the two-phase frictional pressure gradients for the adiabatic and diabatic flow.Verification of the acceleration pressure drop predictions for two-phase adiabatic flow showed that all correlations predict that over 60% of experimental data fit in the range of ±30%. The model proposed in this article predicts 63% of presented data within 10% error, and 96% of the data are predicted within 30% error.

Two-phase flow pressure drop in superhydrophobic channels

Superhydrophobic surfaces have been shown to reduce drag in single-phase channel flow; however, little work has been done to characterize their drag-reducing ability found in two-phase flows. Adiabatic, air-water mixtures were used to explore the influence of hydrophobicity on two-phase flows and the hydrodynamics which might be present in flow condensation environments. Pressure drop measurements in a rectangular channel with one superhydrophobic wall (cross-section approximately 0.37×10mm) and three transparent hydrophilic walls were obtained. Data for air/water mixtures with superficial Reynolds numbers ranging from 22–215 and 55–220, respectively, were obtained for superhydrophobic surfaces with three different cavity fractions. Agreement between experimentally obtained two-phase pressure drop data and correlations in the literature for conventional smooth control surfaces was better than 20 percent, which is within the accuracy of the correlations. The data reveal a reduction in the pressure drop for two-phase flow in a channel with a single superhydrophobic wall compared to a control scenario. The observed reduction is approximately 10 percent greater than the reduction that is observed for single-phase flow (relative to a classical channel).

Pressure drop characteristics of vertically upward flow in inclined rod bundles

An experimental and theoretical research has been carried out for vertically upward two-phase flow of air–water across staggered rod bundles having inclination angles of 0°, 45° and 90°. New correlations for single-phase pressure drops in rod bundles for various inclination angles were developed. The single-phase frictional resistance in the vertical flow was found to have a minimal effect on the total flow resistance in the inclined flow. Based on the single-phase pressure drop data, a new superposition model was proposed and verified to be successful in predicting both the present data and the experimental data in previous experiments of other researchers. The two-phase friction multiplier in the inclined rod bundle, which decreased with increasing mass velocity at a given value of Martinelli parameter, could be fit well in terms of Martinelli parameter and the defined dimensionless mass velocity. In addition, the two-phase friction multiplier first increased and then decreased with increasing Martinelli parameter at a given value of mass velocity for G<200kgm−2s−1. The new correlations developed for two-phase friction multipliers were successful in predicting the two-phase pressure drop data in the inclined rod bundle.

Characteristics of gas–liquid two-phase flows through a sudden contraction in rectangular microchannels

A series of experiments were conducted to study the effects of contraction ratio and different liquid properties on gas–liquid two-phase flow through sudden contraction in micro-channel. Two rectangular microchannels with different contraction ratio were used. The widths of the larger channels upstream of the contraction were 0.53 or 0.78mm (0.230mm in height), while those of the smaller ones were fixed at 0.270mm (0.230mm in height). Distilled water, ethanol 49wt% aqueous solution, pure ethanol and hydrofluoroether (HFE)-7200 were used as the test liquids, and nitrogen as the test gas. Flow pattern, bubble length, liquid slug length and bubble velocity were determined by analyzing video images of the flows. In addition, pressure profile upstream and downstream from the contraction was also measured for single-phase and two-phase flows. The pressure loss due to the contraction was determined from the pressure profiles. In the analysis, bubble velocity data and the pressure loss data were compared with calculations by some correlations in literatures. The bubble velocity data both upstream and downstream from the contraction were correlated with Kawahara et al.’s correlation (2010) where the correlation was accounted for aspect ratio of the channel. The correlation of the contraction coefficient for single-phase liquid flows was newly developed with Reynolds number and contraction ratio. The two-phase pressure drop data reasonably agreed with a slip flow model combined with the present contraction coefficient correlation and drift flux model based void fraction correlation. Moreover, numerical simulations were performed using the computational fluid dynamics software FLUENT (Fluent Inc.) and the volume of fluid (VOF) model. The present numerical simulation data agreed well with the experimental data for flow pattern, bubble velocity, bubble length, bubble pitch and pressure changes through the contraction.

Two phase flow pressure drop in multiport mini-channel tubes using R134a and R32 as working fluids

In this study, two-phase flow pressure drop was experimentally measured in condensation and evaporation fluid flow. Refrigerants R134a and R32 were tested in a multiport extruded aluminium tube (MPEs) with hydraulic diameters of 0.715 and 1.16 mm. Experimental conditions were in a range: mass velocity 200–1229 kg/m2s, heat flux 2.55–70 kW/m2, saturated temperatures (5,7.5,12.5,30,35,40,45,50,55) °C. To do so, two installations have been used. They were constructed at the Technical University of Cartagena Spain, for the study of boiling and condensation in tubes. They are briefly described in this paper jointly with the experiments performed. The experimental data are compared with some well-known correlations which were developed for macro/mini-channel tubes. The homogeneous mixture model slightly underestimates the experimental boiling data. Classic macro-channel correlations: Friedel and Müller-Steinhagen and Heck predict satisfactorily well our experimental pressure drop data. Some of the new correlations specially developed for mini/micro-channels have been tested, finding that Cavallini et al. and Zhang and Webb predict with reasonable accuracy the experimental two-phase flow pressure drop data.

F221 マイクロ・ミニ流路内の曲がり部を通過する二相流の圧力損失(OS9 熱・流動(5))

Two-phase gas-liquid pressure drop data through 180° return bends have been obtained for horizontal rectangular micro-channel and mini-channel. To know the effects of channel sizes, the hydraulic diameters were 0.25 mm and 3 mm respectively as the micro- and the mini-channels. The curvature radii of the bends were 0.500 mm and 0.875 mm for the micro-channel, while 6 mm for the mini-channel. Water, surfactant and glycerin aqueous solutions, ethanol and hydrofluoroether-7200 were used as the test liquid, while nitrogen gas and air as the test gas. The bend pressure drop data were correlated by using an approach of Padilla et al., in which the pressure drop is the sum of two components, i.e., frictional and singular pressure drops. The approach was applicable to the present data if the frictional pressure drop was calculated by Lockhart-Martinelli method and the singular pressure drop was calculated by a newly developed correlation.

Two-phase flow pattern and pressure drop in silicon multi-microchannel with expansion–constriction cross-section

Gas–liquid two-phase intermittent flow pattern and frictional pressure drop in new silicon multi-microchannel were investigated experimentally by means of the IDT high-speed camera mounted together with a Nikon microscope. Each test section consisted of 10 parallel microchannels with 0.1mm wide and 0.2mm deep in constant cross-section segment and each microchannel consisted of an array of periodic reentrant cavities. The major two-phase flow pattern observed was intermittent in the test sections, and the intermittent sub regimes in the new microchannels were different from those displayed in the rectangular straight microchannel. Using nitrogen and deionized water as working fluids, the intermittent sub regime maps for the new multi-microchannel were obtained. Meanwhile, the pressure drops were compared with several existing correlations based on the homogeneous or separated mixture assumption. Results show that the homogeneous flow model cannot predict the two-phase pressure drop data well, while the separated flow model is proposed to provide a better prediction of the two-phase frictional pressure drop. Among the separated flow models investigated, the best two correlations of C value can provide mean deviations within less than 16% for all the three microchannels and all the predictions lie in the bound of ±30%.

Evaluation of the Two Phase Pressure Drop during the CO2-N2 Mixture Pipeline Transport

Abstract Captured CO2 mixture for sequestration purpose can contain impurities such as N2, NOx, SOx, O2, H2O, H2, H2S, Ar. Such impurities affect the critical temperature and pressure, density, viscosity, saturation temperature-pressure line, etc. Among the impurities, N2 can affect the CO2 stream properties largely cause of the low boiling point and high specific volume, so a small ratio of N2 inflow might change the flow pattern of CO2 stream from single phase to two phase flow. To understand the flow behavior of two phase CO2 stream with N2 impurity, experimental investigations should be carried out and compared with existing correlation to figure out the accuracy of correlations. In this study we designed and installed an experimental facility to simulate the two phase flow behavior of CO2-N2 mixture during the pipeline transportation. The test section is composed of a single 6 meter STS304 tube with inner diameter of 3.8608 mm with inlet absolute pressure transmitter and inlet-outlet differential pressure transmitter. Test condition was 21C and 85 bar with varying N2 impurity ratio. In this study the two-phase flow pressure drop data of CO2-N2 mixture flow are compared with correlations of Lockhart-Martinelli, Zhang et al, and Misima & Hibiki. Among three candidate correlations Mishima & Hibiki correlation showed the best accuracy. All of three correlations showed rather low accuracy, but it might be from the reason that the correlations were originally designed to estimate water-vapor two-phase flow pressure drop. The result also shows the need to investigate further visualization and flow pattern identification.

Hydraulic Characteristics of Flow Boiling of Hydrocarbon Fluids: Two-Phase Pressure Drop

Two-phase hydraulic characteristics, in terms of pressure drop and void fraction data, are reported for boiling of single-component hydrocarbon fluids in vertical upflow. These data were obtained simultaneously with the boiling heat transfer measurements. The systematic trends of the measured pressure gradient with respect to vapor quality, mass flux, and pressure are examined. This provides useful information in terms of the relative importance of the constituent parts of the two-phase pressure gradients and confirms the internal consistency of the measured data. These two-phase pressure-drop data under flow boiling conditions are then compared with various correlations from the open literature and also with a proprietary correlation used in commercial heat exchanger design and simulation software. Typical results of these comparisons are presented. It is noted that in the near-zero vapor quality region the measured pressure-gradient data may be lower than expected because of the effect of subcooled boiling.

Water-assisted Flow of Heavy Oil in a Vertical Pipe: Pilot-scale Experiments

The use of the core-annular flow pattern, where a thin fluid surrounds a very viscous one, has been suggested as an attractive artificial-lift method for heavy oils in the current Brazilian ultra-deepwater production scenario. This paper reports the pressure drop measurements and the core-annular flow observed in a 2 7/8-inch and 300 meter deep pilot-scale well conveying a mixture of heavy crude oil (2000 mPa.s and 950 kg/m3 at 35 C) and water at several combinations of the individual flow rates. The two-phase pressure drop data are compared with those of single-phase oil flow to assess the gains due to water injection. Another issue is the handling of the core-annular flow once it has been established. High-frequency pressure-gradient signals were collected and a treatment based on the Gabor transform together with neural networks is proposed as a promising solution for monitoring and control. The preliminary results are encouraging. The pilot-scale tests, including long-term experiments, were conducted in order to investigate the applicability of using water to transport heavy oils in actual wells. It represents an important step towards the full scale application of the proposed artificial-lift technology. The registered improvements in terms of oil production rate and pressure drop reductions are remarkable.

Viscous oil–water flows in a microchannel initially saturated with oil: Flow patterns and pressure drop characteristics

Immiscible viscous liquid–liquid two-phase flow patterns and pressure drop characteristics in a circular microchannel have been investigated. Water and silicone oil with a dynamic viscosity of 863 mPa s were injected into a fused silica microchannel with an inner diameter of 250 μm. As the microchannel was initially filled with the silicone oil, an oil film was found to always form and remain on the microchannel wall. Different flow patterns were observed and classified over a wide range of water and oil flow rates. A flow pattern map is presented in terms of Re, Ca, and We numbers. Two-phase pressure drop data have also been collected and analyzed to develop a simple correlation for slug, annular and annular-droplet flow patterns in terms of superficial water and oil velocities.

Drag reduction in co-current down flow packed column using xanthan gum

Drag reduction is one of the most important techniques for reducing energy consumption in a packed bed contactor. The present work involves an experimental investigation on flow regime transition for air-water system with and without drag reducing agent (DRA), two-phase pressure drop, friction factor and drag reduction using xanthan gum as DRA. Drag reduction was quantified from the two-phase pressure drop data. Based on the present observations it was found that the percentage drag reduction increases with an increase in the concentration of DRA and it is only effective in the range of 300 ppm to 800 ppm. The experimental results indicate that a maximum of 80% drag reduction was achievable using xanthan gum (800 ppm) as DRA. Furthermore, the experimental data were validated with the available literature correlations.