scholarly journals Pressure Drop of a Refrigerant Flowing Vertically Upward and Downward in Small Circular, Rectangular, and Triangular Tubes

2021 ◽  
Vol 11 (11) ◽  
pp. 5195
Author(s):  
Koji Enoki
Keyword(s):  
Pressure Drop ◽  
Cross Sections ◽  
High Performance ◽  
Measurement Data ◽  
Saturation Temperature ◽  
Two Phase ◽  
Pressure Drops ◽  
Frictional Pressure Drop ◽  
Mass Fluxes ◽  
Mini Channels

In the present study, experiments were performed to examine the characteristics of the two-phase frictional pressure drop of an R410A refrigerant flowing vertically upward and downward for the development of a high-performance heat exchanger using small tubes or mini-channels for air-conditioning systems. The cross-sections of copper test tubes were 0.5, 0.7, 1.0, 1.5, and 2.0 mm circular tubes, and rectangular and triangular tubes with hydraulic diameters of 1.04 and 0.88 mm, respectively. The frictional pressure drops were measured in the range of mass fluxes of 30–400 kg·m−2·s−1, with qualities from 0.05 to 0.9 and a saturation temperature of 10 °C. The characteristics of the measured pressure drops were compared in different inner diameters, cross-section shapes, and flow directions. In addition, Chisholm’s parameter and various modified Chisholm’s parameters for small tubes were examined to determine whether or not they reproduced our measurement data.

scholarly journals Investigations on mixture preparation for two phase adiabatic pressure drop of R134a flowing in 5 mm diameter channel

2017 ◽  
Vol 38 (3) ◽  
pp. 101-118 ◽  
Author(s):  
Tomasz Muszyński ◽  
Rafał Andrzejczyk ◽  
Carlos A. Dorao
Keyword(s):  
Pressure Drop ◽  
High Speed ◽  
Saturation Temperature ◽  
High Speed Camera ◽  
Two Phase ◽  
Pressure Drops ◽  
Adiabatic Flow ◽  
Frictional Pressure Drop ◽  
Mixture Preparation ◽  
Diameter Channel

AbstractThe article presents detailed two-phase adiabatic pressure drops data for refrigerant R134a. Study cases have been set for a mass flux varying from 200 to 400 kg/m2s, at the saturation temperature of 19.4 °C. Obtained experimental data was compared with the available correlations from the literature for the frictional pressure drop during adiabatic flow. Influence of mixture preparation on pressure drop was investigated, for varying inlet subcooling temperature in the heated section. The flow patterns have also been obtained by means of a high-speed camera placed in the visualization section and compared with literature observations.

Evaluation Analysis of Prediction Methods for Two-Phase Flow Pressure Drop in Mini-Channels

2008 ◽  
Author(s):  
Licheng Sun ◽  
Kaichiro Mishima
Keyword(s):  
Pressure Drop ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Turbulent Region ◽  
Frictional Pressure Drop ◽  
New Correlation ◽  
Mini Channels ◽  
Flow Pressure ◽  
Better Than

2092 data of two-phase flow pressure drop were collected from 18 published papers of which the working fluids include R123, R134a, R22, R236ea, R245fa, R404a, R407C, R410a, R507, CO2, water and air. The hydraulic diameter ranges from 0.506 to 12mm; Relo from 10 to 37000, and Rego from 3 to 4×105. 11 correlations and models for calculating the two-phase frictional pressure drop were evaluated based upon these data. The results show that the accuracy of the Lockhart-Martinelli method, Mishima and Hibiki correlation, Zhang and Mishima correlation and Lee and Mudawar correalion in the laminar region is very close to each other, while the Muller-Steinhagen and Heck correlation is the best among the evaluated correlations in the turbulent region. A modified Chisholm correlation was proposed, which is better than all of the evaluated correlations in the turbulent region and its mean relative error is about 29%. For refrigerants only, the new correlation and Muller-Steinhagen and Heck correlation are very close to each other and give better agreement than the other evaluated correlations.

Evaluation of Two-Phase Frictional Pressure Drop Correlations Against Experimental Data

2019 ◽  
Vol 12 (3) ◽  
Author(s):  
Wei Li ◽  
Kunrong Shen ◽  
Boren Zheng ◽  
Xiang Ma ◽  
S. A. Sherif ◽  
...  
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Mass Flow ◽  
Flow Model ◽  
Saturation Temperature ◽  
Separated Flow ◽  
Outer Diameter ◽  
Two Phase ◽  
Homogeneous Flow ◽  
Frictional Pressure Drop

Abstract Results are presented here from an experimental investigation on tube side two-phase characteristics that took place in four tested tubes—the 1EHT-1, 1EHT-2, 4LB, and smooth tubes. The equivalent outer diameter of the tube was 9.52 mm and the inner diameter was 8.32 mm. Condensation tests were conducted using refrigerant R410A at a saturation temperature of 318 K, over a mass flow range of 150–450 kg m−2 s−1, with inlet and outlet vapor qualities of 0.8 and 0.2, respectively. Evaporation tests were performed at a saturation temperature of 279 K, over a mass flow range of 150–380 kg m−2 s−1, with inlet and outlet vapor qualities of 0.2 and 0.8, respectively. Pressure drop data of the four tested tubes were collected to evaluate five identified prediction correlations based on the separated flow model and the homogeneous flow model. The separated flow approaches presented predictions with average MAEs of 24.9% and 16.4% for condensation and evaporation data, respectively, while the average MAEs of the homogeneous flow model were 31.6% and 43.4%, respectively. Almost all the identified correlations underestimated the frictional pressure drop of the 4LB tube with MAEs exceeding 30%. An earlier transition of different flow patterns was expected to occur in the EHT tubes while developing a new diabatic flow pattern map is needed for the 4LB tube. A new correlation was presented based on the two-phase multiplier Φ and the Martinelli parameter Xtt, which exhibited excellent predictive results for the experimental data.

Pressure Drop During Refrigerant Condensation Inside Horizontal Smooth, Helical Microfin, and Herringbone Microfin Tubes

2004 ◽  
Vol 126 (5) ◽  
pp. 687-696 ◽  
Author(s):  
Jonathan A. Olivier ◽  
Leon Liebenberg ◽  
Mark A. Kedzierski ◽  
Josua P. Meyer
Keyword(s):  
Heat Exchanger ◽  
Pressure Drop ◽  
Saturation Temperature ◽  
Mean Deviation ◽  
Pressure Gradients ◽  
Test Results ◽  
Pressure Drops ◽  
Mass Fluxes ◽  
R 134A ◽  
Microfin Tubes

This paper presents a study of pressure drops during condensation inside a smooth, an 18-deg helical microfin, and a herringbone microfin tube. Measurements were conducted with refrigerant flowing through the tube of a concentric heat exchanger, with water flowing in a counterflow direction in the annulus. Each tube was part of a condenser consisting of eight subcondensers with instrumentation preceding each subcondenser. Three refrigerants were used, namely, R-22, R-407C, and R-134a, all operating at a saturation temperature of 40 °C with mass fluxes ranging from 400 to 800kg/m2 s. Inlet qualities ranged from 0.85 to 0.95 and outlet qualities ranged from 0.05 to 0.15. The test results showed that on average for the three refrigerants the pressure gradients of the herringbone microfin tube were about 79% higher than that of the smooth tube and about 27% higher than that of the helical microfin tube. Further, a correlation from the literature for predicting pressure drops inside a helical microfin tube was modified for the herringbone microfin tube. The modified correlation predicted the data to within an error of 1% and had an absolute mean deviation of 6.8%. This modified correlation compared well with a correlation from the literature that predicted the data to within an error of 7%.

Flow Characteristics and Frictional Pressure Drops of Gas-Liquid Two-Phase Flow in Mini-Micro Pipes and at Vena Contract and Expansion

2007 ◽  
Author(s):  
Hiroyasu Ohtake ◽  
Hideyasu Ohtaki ◽  
Yasuo Koizumi
Keyword(s):  
Pressure Drop ◽  
Flow Pattern ◽  
Two Phase Flow ◽  
Liquid Velocity ◽  
Flow Patterns ◽  
Experimental Results ◽  
Phase Flow ◽  
Two Phase ◽  
Pressure Drops ◽  
Frictional Pressure Drop

The frictional pressure drops and two-phase flow patterns of gas-liquid two-phase flow in mini-micro pipes and at vena contract and expansion were investigated experimentally. Test liquid was water; test gas was argon. The diameter of the test mini-pipe was 0.5, 0.25 and 0.12 mm, respectively. The pressure drop data and the flow pattern were collected over 2.1 < Ug < 92.5 m/s for the superficial gas velocity and 0.03 < Ul < 10 m/s for the superficial liquid velocity. The experimental results show that the flow patterns were slug, churn, ring and annular flows; pure bubbly flow pattern was not observed in a range of the present experimental conditions. The two-phase friction multiplier data for D > 0.5 mm showed to be in good agreement with the conventional correlations. On the other hand, the two-phase friction multiplier data for D < 0.25 mm differed from the calculated values by the conventional correlations. Then, thickness of liquid film around a gas plug and size of gas core were estimated and the effect of frictional pressure drop on channel size was discussed through Knudsen Number of gas and instability on liquid-gas interface. The coefficients of sudden enlargement and sudden contraction in mini-pipes for the gas-water two-phase flow were modified from the present experimental results.

Two-Phase Pressure Drop of CO2 in Mini Tubes and Microchannels

2003 ◽  
Author(s):  
R. Yun ◽  
Y. Kim
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Mass Flux ◽  
Large Diameter ◽  
Two Phase ◽  
Heating Method ◽  
Pressure Drops ◽  
Direct Heating ◽  
Frictional Pressure Drop ◽  
Phase Pressure

Two-phase pressure drops of CO2 are investigated in mini tubes with inner diameters of 2.0 and 0.98 mm and in microchannels with hydraulic diameters from 1.08 to 1.54 mm. For the mini tubes, the tests were conducted with a variation of mass flux from 500 to 3570 kg/m2s, heat flux from 7 to 48 kW/m2, while maintaining saturation temperatures at 0°C, 5°C and 10°C. For the microchannels, mass flux was varied from 100 to 400 kg/m2s, and heat flux was altered from 5 to 20 kW/m2. A direct heating method was used to provide heat into the refrigerants. The pressure drop of CO2 in mini tubes shows very similar trends with that in large diameter tubes. Although the microchannel has a small hydraulic diameter, two-phase effects on frictional pressure drop are significant. The Chisholm parameter of the Lockhart and Martinelli correlation is modified by considering diameter effects on the two-phase frictional multiplier.

Two-Phase Flow Pressure Drop Measurement in PEM Fuel Cell Flow Channels

2014 ◽  
Author(s):  
Mehdi Mortazavi ◽  
Kazuya Tajiri
Keyword(s):  
Fuel Cell ◽  
Pressure Drop ◽  
Two Phase Flow ◽  
Pem Fuel Cell ◽  
Phase Flow ◽  
Two Phase ◽  
Pressure Drops ◽  
Flow Channels ◽  
Mass Fluxes ◽  
Flow Pressure

Proton exchange membrane (PEM) fuel cells produce power with water and heat as inevitable byproducts. Accumulated liquid water within gas channel blocks the reactant flow and cause pressure drop along the gas channel. It is of extreme importance to accurately predict the liquid and gas two-phase flow pressure drop in PEM fuel cell flow channels. This pressure drop can be considered as an in-situ diagnostic tool that reveals information about the amount of liquid water accumulated within the flow channels. In this paper, the two-phase flow pressure drops are measured in ex-situ PEM fuel cell parallel flow channels. The pressure drops were measured for air mass fluxes of 2.4–6.3kg/m2s and water mass fluxes of 0.0071–1.28kg/m2s. These mass fluxes correspond to 2–5.33m/s and 7.14 × 10−6 – 0.0012m/s air and water superficial velocities, respectively. The measured two-phase flow pressure drops are then compared with different two-phase flow pressure drop models. Qualitative and quantitative comparison between the experimental results and existing models is provided in this work.

Experimental Investigation of Flow Boiling Pressure Drop of R134A in a Microscale Horizontal Smooth Tube

2011 ◽  
Vol 3 (1) ◽  
Author(s):  
Cristiano Bigonha Tibiriçá ◽  
Jaqueline Diniz da Silva ◽  
Gherhardt Ribatski
Keyword(s):  
Pressure Drop ◽  
High Speed ◽  
Flow Boiling ◽  
Smooth Tube ◽  
Working Fluid ◽  
Prediction Methods ◽  
Internal Diameter ◽  
Two Phase ◽  
Pressure Drops ◽  
Frictional Pressure Drop

This paper presents new experimental flow boiling pressure drop results in a microscale tube. The experimental data were obtained under diabatic conditions in a horizontal smooth tube with an internal diameter of 2.32 mm. Experiments were performed with R134a as working fluid, mass velocities ranging from 100 kg/m2 s to 600 kg/m2 s, heat flux ranging from 10 kW/m2 to 55 kW/m2, saturation temperatures of 31°C, and exit vapor qualities from 0.20 to 0.99. Flow pattern characterization was also performed from images obtained by high-speed filming. Pressure drop gradients up to 48 kPa/m were measured. These data were carefully analyzed and compared against 13 two-phase frictional pressure drop prediction methods, including both macro- and microscale methods. Comparisons against these methods based on the data segregated according to flow patterns were also performed. Overall, the method by Cioncolini et al. (2009, “Unified Macro-to-Microscale Method to Predict Two-Phase Frictional Pressure Drops of Annular Flows,” Int. J. Multiphase Flow, 35, pp. 1138–1148) provided quite accurate predictions of the present database.

scholarly journals Robust and universal predictive models for frictional pressure drop during two-phase flow in smooth helically coiled tube heat exchangers

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
M. A. Moradkhani ◽  
Seyyed Hossein Hosseini ◽  
M. Mansouri ◽  
G. Ahmadi ◽  
Mengjie Song
Keyword(s):  
Pressure Drop ◽  
Sensitivity Analyses ◽  
Two Phase ◽  
Neural Network Approach ◽  
Frictional Pressure Drop ◽  
Mass Fluxes ◽  
The Neural Network ◽  
Coil Axis ◽  
Data Points ◽  
Intelligent Models

AbstractThere is a lack of well-verified models in the literature for the prediction of the frictional pressure drop (FPD) in the helically coiled tubes at different conditions/orientations. In this study, the robust and universal models for estimating two-phase FPD in smooth coiled tubes with different orientations were developed using several intelligent approaches. For this reason, a databank comprising 1267 experimental data samples was collected from 12 independent studies, which covers a broad range of fluids, tube diameters, coil diameters, coil axis inclinations, mass fluxes, saturation temperatures, and vapor qualities. The earlier models for straight and coiled tubes were examined using the collected database, which showed absolute average relative error (AARE) higher than 21%. The most relevant dimensionless groups were used as models’ inputs, and the neural network approach of multilayer perceptron and radial basis functions (RBF) were developed based on the homogenous equilibrium method. Although both intelligent models exhibited excellent accuracy, the RBF model predicted the best results with AARE 4.73% for the testing process. In addition, an explicit FPD model was developed by the genetic programming (GP), which showed the AARE of 14.97% for all data points. Capabilities of the proposed models under different conditions were described and, the sensitivity analyses were performed.

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