Frictional 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.

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.

Comparison of R404A condensation heat transfer and pressure drop with low global warming potential replacement candidates R448A and R452A

The objective of this paper was to measure and compare the heat transfer coefficient and pressure drop of R404A and two potential replacement candidate refrigerants with a lower global warming potential, R448A and R452A. Experiments were conducted inside a 4.7 mm horizontal tube at mass fluxes ranging from 100 to 800 kg m−2 s−1, and at three different saturation conditions (40, 50, and 60 ∘C). R448A and R452A are zeotropic refrigerant mixtures, with temperature glides of approximately 4 ∘C and 3 ∘C, respectively. The Cavallini et al. (2006) correlation predicted the heat transfer data best for all three refrigerants, once mixture effects were accounted for using the equilibrium Silver (1947), Bell and Ghaly (1973) method. The Haraguchi et al. (1994) correlation predicted the R484A frictional pressure drop data best (mean average percent error, MAPE = 15%), while the Friedel (1979) correlation predicted the R404A (MAPE = 15%) and R452A data (MAPE = 14%) pressure drop the best. The heat transfer coefficients of R404A were slightly higher than those of R452A and slightly lower than those of R448A at equivalent conditions. At the same mass flux, (G = 600 kg m−2 s−1), R448A and R452A pressure drops are on average 81% and 3.3% higher than that of R404A. For the same cooling capacity and condenser design, the pressure drop of R404A and R452A are approximately the same and the pressure drop of R448A is approximately 16% lower than that of R404A.

R1234yf and R1234ze(E) as environmentally friendly replacements of R134a: Assessing flow boiling on an experimental basis

R134a is ongoing a phase-down process in several countries and R1234yf can be a viable low GWP alternative together with R1234ze(E). Since new experimental data are always requested by researchers and industry to increase the global database, to assess the existing correlations, and to expand the knowledge about the refrigerant applications, in this paper more than 100 new heat transfer coefficient and frictional pressure drop data are presented during R1234yf flow boiling inside a 4 mm inner diameter smooth copper tube. Three saturation temperatures 10 °C, 15 °C and 20 °C were investigated and critically discussed, for each temperature the heat flux ranged from 15 to 30 kW m−2 and the mass velocity from 300 to 600 kg m−2 s−1. Furthermore, some literature correlations were implemented and carefully examined and their deviations are reported. Finally, the R1234yf heat transfer performance is compared against R1234ze(E) and R134a, highlighting the peculiarities of each alternative molecule. R1234ze(E) outperforms the other refrigerants at high vapor qualities but both R1234yf and R1234ze(E) can be viable low GWP substitutes to R134a, if the new design is able to take advantage of the qualities of each refrigerant.

Experimental investigation of condensation pressure drop of R134a in smooth and grooved multiport flat tubes of automotive heat exchanger

Condensation frictional pressure drop was obtained in multiport micro channel smooth and grooved flat tubes using R134a. The study consists of two smooth and one grooved tube. Refrigerant R134a is studied over a mass flux 490–1600 kg/m2s, heat flux 5.5–19 kW/m2 and saturation temperature 51–68 °C. Results reveal that frictional pressure drop increases with an increment of mass flux, vapor quality and decreases with the increase of saturation temperature. The effect of heat flux on frictional pressure drop was negligible. Grooved tube shows the lowest pressure drop and surprisingly highest heat transfer coefficient. The frictional pressure drop data was compared with famous correlations. Zhang and Webb predicted 86% of the data with in ±30%.

수평 원관 내 공기-오일 이상유동 양식과 마찰 압력강하에 관한 실험적 연구

This study examines the air-oil two-phase flow regime and frictional pressure drop in a horizontal circular pipe with a diameter of 40 mm. The pressure drop fluctuation characteristics for different air and oil superficial velocities are investigated. Observed flow regimes and frictional pressure drop data are compared with previous flow regime maps and frictional pressure drop correlations, respectively.

Experimental study of vertical and horizontal two-phase pipe flow through double 90 degree elbows

This paper presents an experimental study of the characteristics of the two-phase flow through vertical and horizontal pipes connected using 90-degree elbows with an inner diameter of 101.6 mm. 66 flow conditions are performed in this experiment, covering bubbly, plug, slug, pseudo slug, and stratified flow for horizontal pipe, and bubbly, cap bubbly, churn turbulent, and falling film/annular flow for vertical pipe. A detailed flow regime analysis for both horizontal and vertical pipe flow are discussed. Flow regime maps for both horizontal flow and vertical downward flow agree with the existing maps (Mandhane et al., 1974; Qiao et al., 2017). The effect of the elbow on the flow regime transition is primarily discussed based on the experimental results and observations. The effect of elbow observed in this experiment mainly contributes to the large bubble breakup and the change of void distribution. Area averaged void fraction development is presented and the sharp drop of void fraction in vertical downward test section is observed which results from kinematic shock phenomenon. A frictional pressure drop analysis is also studied using Lockhart-Martinelli correlation and it is found that C = 40, 100, and 125 are correlated with the frictional pressure drop data for horizontal, vertical, and whole test sections with minimum differences. With the database, the drift flux model for vertical downward flow (Goda et al., 2003) is validated and the relative difference between model and data is 15.95%.

Saturated vapour condensation of HFC404A inside a 4 mm ID horizontal smooth tube: Comparison with the long-term low GWP substitutes HC290 (Propane) and HC1270 (Propylene)

This paper presents the comparative analysis of HFC404A and its low GWP substitutes HC290, and HC1270 in saturated vapour condensation inside a 4mm ID horizontal smooth tube. The experimental tests were carried out at 30, 35, and 40°C of saturation temperatures, with refrigerant mass flux in the range 75–800kgm−2s−1 at decreasing vapour quality. A transition point from gravity-dominated and forced convection condensation was found for an equivalent Reynolds number around 10,000. The experimental heat transfer coefficients in the forced convection condensation regime were very well predicted by the Akers et al. (1959) model, whereas the Friedel (1979) correlation was able to reproduce the frictional pressure drop data in the whole experimental range. HC290 and HC1270 exhibit heat transfer coefficients higher and frictional pressure drops lower than those of HFC404A; therefore both the HC refrigerants seem to be very promising as long-term low GWP substitutes for HFC404A.

Frictional pressure drop correlation for two-phase flows in mini and micro multi-channels

1029 frictional pressure drop data of two-phase flow in mini/micro multi-channels were collected from 11 literatures. This database included 8 working fluids: R134a, R22, R404a, FC-72, water, CO2, R236fa and R245fa. The channel dimension ranged from 0.109 to 2.13mm. Frictional pressure drop range of the database was from 5 to 150kPa. The applicability of 11 existing correlations developed for mini/micro single channels to mini/micro multi-channels were evaluated with the multi-channel database. Among the existing correlations, the correlation of Lee-Mudawar predicted the database with the mean absolute percentage error (MAPE) of 35.3%, the correlations of Lee-Garimella and Sun-Mishima had MAPEs within 45.0%. In the process of new correlation development, the database was divided into three categories (namely, 1: gas laminar-liquid laminar, 2: gas turbulent-liquid laminar, 3: gas turbulent-liquid turbulent) in terms of liquid Reynolds number and gas Reynolds number, since gas laminar-liquid turbulent data did not exist in the literature. The newly developed correlation was formulated by a function of the two-phase Reynolds number, Retp, the two-phase viscosity number, Nμtp, and the vapor quality, x. The correlation could predict the measured frictional pressure drop with the MAPE of 18.9%. The correlation demonstrated an excellent performance of the two-phase flow frictional pressure drop prediction in mini/micro multi-channels.

Frictional pressure drop correlation for two-phase flows in mini and micro single-channels

1521 frictional pressure drop data points were collected from 12 literatures. The database included adiabatic and diabatic systems composed of 10 working fluids. The diameter range was from 0.1 to 3mm, and the pressure drop ranged from 1.26kPa/m to 2MPa/m. 17 existing single channel two-phase pressure drop correlations including homogenous flow model and separated flow model were evaluated with the database. The comparison results showed that the correlations of Pamitran et al., Hwang and Kim, Mishima and Hibiki and Zhang et al. gave better predictions than the others. However, the performance evaluation results also showed the mean absolute errors higher than 40%. Based on the relatively large prediction error by the existing correlations, a new correlation was proposed by classifying the flow conditions into four regimes (namely, 1: gas laminar-liquid laminar, 2: gas laminar-liquid turbulent, 3: gas turbulent-liquid laminar, 4: gas turbulent-liquid turbulent). The newly developed correlation is expressed by a function of the two-phase Reynolds number, Retp, the two-phase viscosity number, Nμtp, and the gas quality, x, and was able to predict the two-phase frictional pressure drop with the mean absolute percentage error of 17.4%. The correlation demonstrated an excellent performance for predicting the two-phase frictional pressure drop in mini/micro single channels.

Frictional Pressure Drop Correlations for Single-Phase Flow, Condensation, and Evaporation in Microfin Tubes

Experimental single-phase, condensation, and evaporation (flow boiling) pressure drop data from the literature and our previous studies were collected to evaluate previous frictional pressure drop correlations for horizontal microfin tubes of different geometries. The modified Ravigururajan and Bergles correlation, by adopting the Churchill model to calculate the smooth-tube friction factor and by using the hydraulic diameter in the Reynolds number, can predict single-phase turbulent frictional pressure drop data relatively well. Eleven pressure drop correlations were evaluated by the collected database for condensation and evaporation. Correlations originally developed for condensation and evaporation in smooth tubes can be suitable for microfin tubes if the friction factors in the correlations were calculated by the Churchill model to include microfin effects. The three most accurate correlations were recommended for condensation and evaporation in microfin tubes. The Cavallini et al. correlation and the modified Friedel correlation can give good predictions for both condensation and evaporation. However, some inconsistencies were found, even for the recommended correlations.

Flow boiling and frictional pressure gradients in plate heat exchangers. Part 2: Comparison of literature methods to database and new prediction methods

In the second part of this study a sensitivity analysis on the prediction methods is performed to consider the effect of plate geometry on thermal–hydraulic performance and an extensive comparison of all the two-phase pressure drop and flow boiling heat transfer prediction methods available in the open literature are also provided versus the large diversified database presented in Part 1. The experimental databank, from numerous independent research studies, is then utilized to develop the new prediction methods to evaluate local heat transfer coefficients and pressure drops. These new methods were developed from 1903 heat transfer and 1513 frictional pressure drop data points (3416 total), respectively, and were proved to work better over a very wide range of operating conditions, plate designs and fluids (including ammonia). The prediction for flow boiling heat transfer coefficients was broken down into separate macro- and micro-scale methods.

Two-phase frictional pressure drops in U-bends and contiguous straight tubes for different refrigerants, orientations, tube, and bend diameters: Part 2. New models (RP-1444)

In the first part of this article (Silva Lima and Thome 2012b), new experimental frictional pressure drop data in U-bends were presented and discussed. The experimental data were obtained for R410A and R134a at two saturation temperatures (5°C and 10°C [41°F and 50°F]) flowing at three mass fluxes (150, 300, and 500 kg s−1m−2 [110.6·103, 221.2·103, and 368.7·103 lb h−1 ft−2]) inside five different test sections with three different internal diameters (13.4, 10.7, and 7.8 mm [0.527, 0.421, and 0.307 in.]) and five different bend diameters (66.1, 54.8, 38.1, 31.7, and 24.8 mm [2.602, 2.157, 1.5, 1.248, and 0.976 in.]) in three different orientations (horizontal, vertical upflow, and vertical downflow) with vapor qualities ranging from 0.05 to 0.95. In this second part, first an update to the flow pattern based frictional pressure drop model for straight tubes of Moreno Quibén and Thome (2007a, 2007b) is proposed. Then, a new multi-orientation flow pattern based prediction method for frictional pressure drops in U-bends is presented and described. With this new model, more than 93% of the experimental data were predicted within an error window of less than 30%. The integration of the two models over the test section (straight tubes and U-bend) predicted the total pressure drop database with similar accuracy. The results showed that the combination of these two new prediction tools offers a powerful but simple way for one to obtain high accuracy pressure drop predictions.

Two-Phase Pressure Drop Calculations in Small Diameter Inclined Tubes

Effect of inclination on two-phase frictional pressure drop was investigated in small diameter circular tubes with inner diameters of 4.0, 6.0, 8.0 and 10.0 mm using air and water. Pressure drop was measured and compared with various existing models commonly used for macro and micro channels such as homogeneous, Lockhart-Martinelli, Chisholm, Friedel, Mishma Hibiki, and Zang Mishma. It was found that existing correlations are inadequate in predicting pressure drop for small diameter inclined tubes. The void fraction is calculated using a general void fraction correlation in two-phase flow for various pipe orientations. Based on analysis of present experimental frictional pressure drop data, a correlation is proposed for predicting Chisholm parameter C in small diameter inclined tubes. There was a significant ordering of pressure drop data with respect to Reynolds number, Webber number and Bond number for each diameter.

Two-Phase Frictional Pressure Drop and Flow Boiling Heat Transfer for R245fa in a 2.32-mm Tube

Experimental two-phase frictional pressure drop and flow boiling heat transfer results are presented for a horizontal 2.32-mm ID stainless-steel tube using R245fa as working fluid. The frictional pressure drop data was obtained under adiabatic and diabatic conditions. Experiments were performed for mass velocities ranging from 100 to 700 kg m−2 s−1, heat flux from 0 to 55 kW m−2, exit saturation temperatures of 31 and 41°C, and vapor qualities from 0.10 to 0.99. Pressures drop gradients and heat transfer coefficients ranging from 1 to 70 kPa m−1 and from 1 to 7 kW m−2 K−1 were measured. It was found that the heat transfer coefficient is a strong function of the heat flux, mass velocity, and vapor quality. Five frictional pressure drop predictive methods were compared against the experimental database. The Cioncolini et al. (2009) method was found to work the best. Six flow boiling heat transfer predictive methods were also compared against the present database. Liu and Winterton (1991), Zhang et al. (2004), and Saitoh et al. (2007) were ranked as the best methods. They predicted the experimental flow boiling heat transfer data with an average error around 19%.

Effect of diameter on two-phase pressure drop in narrow tubes

The effect of tube diameter on two-phase frictional pressure drop was investigated in circular tubes with inner diameters of 0.6, 1.2, 1.7, 2.6 and 3.4 mm using air and water. The gas and liquid superficial velocity ranges were 0.01–50 m/s and 0.01–3 m/s, respectively. The gas and liquid flow rates were measured and the two-phase flow pattern images were recorded using high-speed CMOS camera. Unique flow patterns were observed for smaller tube diameters. Pressure drop was measured and compared with various existing models such as homogeneous model and Lockhart–Martinelli model. It appears that the dominant effect of surface tension shrinking the flow stratification in the annular regime is important. It was found that existing models are inadequate in predicting the pressure drop for all the flow regimes visualized. Based on the analysis of present experimental frictional pressure drop data a correlation is proposed for predicting Chisholm parameter “ C” in slug annular flow pattern. For all other flow regimes Chisholm’s original correlation appears to be adequate except the bubbly flow regime where homogeneous model works well. The modification results in overall mean deviation of pressure drop within 25% for all tube diameters considered. This approach of flow regime based modification of liquid gas interaction parameter appears to be the key to pressure drop prediction in narrow tubes.

Two-phase air–water flow in micro-channels: An investigation of the viscosity models for pressure drop prediction

Adiabatic two-phase air–water flow is experimentally studied in this work. Two channels, made of fused silica, with different diameters of 0.53 and 0.15 mm are used as test sections. The void fraction data for both tubes are obtained by image analysis. For the larger channel, the void fraction is found to be a linear relationship with the volumetric quality. In the case of the smaller one, however, the non-linear void fraction is obtained. The measured frictional pressure drop data are compared with the predictions regarding the homogeneous flow assumption. Several well-known two-phase viscosity models are subsequently evaluated for applicability to micro-channels.

Characteristics of Two-Phase Flows in a Rectangular Microchannel with a T-Junction Type Gas-Liquid Mixer

In this study, gas–liquid two-phase flows in a horizontal rectangular microchannel have been investigated. The rectangular microchannel has a hydraulic diameter of 0.235 mm, and a width and depth of 0.24 mm and 0.23 mm, respectively. A T-junction-type gas–liquid mixer was used to introduce gas and liquid in the channel. In order to know the effects of liquid properties, distilled water, ethanol, and HFE7200 were used as the test liquids, with nitrogen gas was used as the test gas. The flow pattern, the bubble length, the liquid slug length, and the bubble velocity in two-phase flow were measured with a high-speed video camera, and the void fraction was determined from the bubble velocity data and the superficial gas velocity data. In addition, the pressure drop was also measured with a calibrated differential pressure transducer. The bubble length data were compared with the calculation by the scaling law proposed by Garstecki et al. [7]. The bubble velocity data and/or the void fraction data were well correlated with the well-known drift flux model [12] with a new distribution parameter correlation developed in this study. The frictional pressure drop data were also well correlated with the Lockhart-Martinelli method with a correlation of the two-phase friction multiplier.

Flow boiling in horizontal flattened tubes: Part I – Two-phase frictional pressure drop results and model

Experiments of diabatic two-phase pressure drops in flow boiling were conducted in four horizontal flattened smooth copper tubes with two different heights of 2 and 3 mm. The equivalent diameters of the flat tubes are 8.6, 7.17, 6.25, and 5.3 mm. The working fluids are R22 and R410A, respectively. The test conditions are: mass velocities from 150 to 500 kg/m 2 s, heat fluxes from 6 to 40 kW/m 2 and saturation temperature of 5 °C (reduced pressures p r are 0.12 for R22 and 0.19 for R410A). The experimental results of two-phase pressure drops are presented and analyzed. Furthermore, the predicted two-phase frictional pressure drops by the flow pattern based two-phase pressure drop model of Moreno Quibén and Thome [J. Moreno Quibén, J.R. Thome, Flow pattern based two-phase frictional pressure drop model for horizontal tubes, Part I: Diabatic and adiabatic experimental study, Int. J. Heat Fluid Flow 28 (2007) 1049–1059; J. Moreno Quibén, J.R. Thome, Flow pattern based two-phase frictional pressure drop model for horizontal tubes, Part II: New phenomenological model, Int. J. Heat Fluid Flow 28 (2007) 1060–1072] using the equivalent diameters were compared to the experimental data. The model, however, underpredicts the flattened tube two-phase frictional pressure drop data. Therefore, correction to the annular flow friction factor was proposed for the flattened tubes and now the method predicts 83.7% of the flattened tube pressure drop data within ±30%. The model is applicable to the flattened tubes in the test condition range in the present study. Extension of the model to other conditions should be verified with experimental data.

Two-phase flow pattern and frictional performance across small rectangular channels

This study presents flow visualizations and two-phase frictional pressure drop data for three rectangular channels with channel height of 3, 6 and 9 mm, and a fixed width of 3 mm. It is found that the stratified flow pattern still exists for an aspect ratio of unity at a low mass flux of 100 kg/m 2 s but it completely vanishes when G > 200 kg/m 2s. For the same plug flow of intermittent flow pattern, the number of plug increases whereas its length decreases when the aspect ratio is increased. This is especially pronounced when the mass flux is further increased over 500 kg/m 2 s. The major departure of the observed flow pattern relative to the conventional Mandhane flow map is the transition boundary for slug/annular had been moved to a much lower superficial vapor velocity. The two-phase frictional pressure drop data are compared to homogeneous and Chisholm method, Wambsganss and Ide-Fukano correlations. It is found that none of the existing methods or correlations can satisfactorily predict the two-phase pressure gradient in rectangular channels. A modified C factor of Chisholm method considering the effect of aspect ratio was proposed from the empirical fit with the data sets of Wambsganss et al., Ide-Fukano, and this study. The corresponding mean deviations of the proposed correlation against the datasets are 24.99%, 10.83% and 10.73%, respectively. This correlation is applicable in wide rages of mass flux (50 < G < 700 kg/m 2 s), vapor quality (0.001 < x < 0.95), Martinelli parameter (0.05 < X < 20) and aspect ratio (0.1 < A < 1.0).