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Title: Two-phase frictional pressure drop of R-134a and R-410A refrigerant-oil mixtures in straight tubes and U-type wavy tubes

Abstract

This study presents single-phase and two-phase pressure drop data for R-134a/oil mixture flowing in a wavy tube with inner diameter of D=5.07mm and curvature ratio 2R/D=5.18 and R-410A/oil mixture flowing in a wavy tube of D=3.25mm and 2R/D=3.91. Both mixtures have oil concentration C=0%, 1%, 3% and 5% for the tests. The ratio of frictional factor between U-bend in wavy tube and straight tube (f{sub C}/f{sub S}) is about 3.5 for Re<2500 and is approximate 2.5 for Re=3500-25,000 for oil and liquid R-134a mixture flowing in the 5.07mm diameter wavy tube. The influence of oil concentration on single-phase friction factor is negligible, provided that the properties are based on the mixture of lubricant and refrigerant. The ratio between two-phase pressure gradients of U-bend and straight tube is about 2.5-3.5. This ratio is increased with oil concentration and vapor quality. The influence of oil is augmented at a higher mass flux for liquid spreading around the periphery at an annular flow pattern. Moreover, the influence of lubricant becomes more evident of a U-bend configuration. This is associated the induced swirled flow motion and an early change of flow pattern from stratified to annular flow pattern. The frictional two-phase multiplier for straightmore » tube can be fairly correlated by using the Chisholm correlation for the data having Martinelli parameter X between 0.05 and 1.0. Fridel correlation also shows a good agreement with a mean deviation of 17.6% to all the straight tube data. For the two-phase pressure drop in U-bend, the revised Geary correlation agrees very well with the R-134a and R-410A oil-refrigerant data with a mean deviation of 16.4%. (author)« less

Authors:
;  [1]; ;  [2]
  1. Mechanical Engineering Department, National Yunlin University of Science and Technology, Yunlin 640 (Taiwan)
  2. Energy and Resource Laboratories, Industrial Technology Research Institute Hsinchu 310 (Taiwan)
Publication Date:
OSTI Identifier:
20843288
Resource Type:
Journal Article
Resource Relation:
Journal Name: Experimental Thermal and Fluid Science; Journal Volume: 31; Journal Issue: 4; Other Information: Elsevier Ltd. All rights reserved
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; AIR CONDITIONERS; HEAT PUMPS; FRICTION; PRESSURE DROP; LUBRICATING OILS; REFRIGERANTS; TWO-PHASE FLOW; MIXTURES; TUBES; CONFIGURATION

Citation Formats

Chen, Ing Youn, Wu, Yu-Shi, Chang, Yu-Juei, and Wang, Chi-Chuan. Two-phase frictional pressure drop of R-134a and R-410A refrigerant-oil mixtures in straight tubes and U-type wavy tubes. United States: N. p., 2007. Web. doi:10.1016/J.EXPTHERMFLUSCI.2006.05.001.
Chen, Ing Youn, Wu, Yu-Shi, Chang, Yu-Juei, & Wang, Chi-Chuan. Two-phase frictional pressure drop of R-134a and R-410A refrigerant-oil mixtures in straight tubes and U-type wavy tubes. United States. doi:10.1016/J.EXPTHERMFLUSCI.2006.05.001.
Chen, Ing Youn, Wu, Yu-Shi, Chang, Yu-Juei, and Wang, Chi-Chuan. Thu . "Two-phase frictional pressure drop of R-134a and R-410A refrigerant-oil mixtures in straight tubes and U-type wavy tubes". United States. doi:10.1016/J.EXPTHERMFLUSCI.2006.05.001.
@article{osti_20843288,
title = {Two-phase frictional pressure drop of R-134a and R-410A refrigerant-oil mixtures in straight tubes and U-type wavy tubes},
author = {Chen, Ing Youn and Wu, Yu-Shi and Chang, Yu-Juei and Wang, Chi-Chuan},
abstractNote = {This study presents single-phase and two-phase pressure drop data for R-134a/oil mixture flowing in a wavy tube with inner diameter of D=5.07mm and curvature ratio 2R/D=5.18 and R-410A/oil mixture flowing in a wavy tube of D=3.25mm and 2R/D=3.91. Both mixtures have oil concentration C=0%, 1%, 3% and 5% for the tests. The ratio of frictional factor between U-bend in wavy tube and straight tube (f{sub C}/f{sub S}) is about 3.5 for Re<2500 and is approximate 2.5 for Re=3500-25,000 for oil and liquid R-134a mixture flowing in the 5.07mm diameter wavy tube. The influence of oil concentration on single-phase friction factor is negligible, provided that the properties are based on the mixture of lubricant and refrigerant. The ratio between two-phase pressure gradients of U-bend and straight tube is about 2.5-3.5. This ratio is increased with oil concentration and vapor quality. The influence of oil is augmented at a higher mass flux for liquid spreading around the periphery at an annular flow pattern. Moreover, the influence of lubricant becomes more evident of a U-bend configuration. This is associated the induced swirled flow motion and an early change of flow pattern from stratified to annular flow pattern. The frictional two-phase multiplier for straight tube can be fairly correlated by using the Chisholm correlation for the data having Martinelli parameter X between 0.05 and 1.0. Fridel correlation also shows a good agreement with a mean deviation of 17.6% to all the straight tube data. For the two-phase pressure drop in U-bend, the revised Geary correlation agrees very well with the R-134a and R-410A oil-refrigerant data with a mean deviation of 16.4%. (author)},
doi = {10.1016/J.EXPTHERMFLUSCI.2006.05.001},
journal = {Experimental Thermal and Fluid Science},
number = 4,
volume = 31,
place = {United States},
year = {Thu Feb 15 00:00:00 EST 2007},
month = {Thu Feb 15 00:00:00 EST 2007}
}
  • Two-phase flow in horizontal pipe was analyzed with simplified models for annular and stratified flow. The velocity profiles for the liquid and gas phase were described with the Prandt mixing length. From this analysis, the frictional pressure drop was calculated with the modified Baker map for flow pattern transition. The intermediate region, i.e. wavy flow, was interpolated between annular and stratified flow. Comparison of this analysis with existing experimental data o refrigerants showed good agreement.
  • This paper reports pressure drops during condensation for R-22, R-134a, R-410a, and R-407c in three enhanced tubes and one smooth tube. The test tubes were a 3/8 inch outer diameter smooth tube, a 3/8 inch outer diameter microfin tube, a 5/16 inch outer diameter microfin tube, and a 5/8 inch outer diameter microfin tube. Pressure drops are reported at four mass fluxes, at two saturation temperatures, and over a range of average qualities in the test tubes. The pressure drops for R-410a were approximately 40% lower than those of R-22 in both tubes. R-407c had 10% to 20% lower pressuremore » drops than R-22, while 134-a had slightly larger pressure drops than R-22. The microfin tube pressure drops were, on average, 40% to 80% higher than those for the smooth tube for all refrigerants. The pressure drop penalty of the microfin tube was shown to decrease with increased quality.« less
  • The adiabatic two-phase frictional multipliers for SUVA, R-134a flowing in a rectangular duct (with D{sub H} = 4.8 mm) have been measured for 3 nominal system pressures (0.9 MPa, 1.38 MPa and 2.41 MPa) and 3 nominal mass fluxes (510, 1020 and 2040 kg/m{sup 2}/s). The data is compared with several classical correlations to assess their predictive capabilities. The Lockhart-Martinelli model gives reasonable results at the lowest pressure and mass flux, near the operating range of most refrigeration systems, but gives increasingly poor comparisons as the pressure and mass flux is increased. The Chisholm B-coefficient model is found to bestmore » predict the data over the entire range of test conditions; however, there is significant disagreement at the highest pressure tested (with the model over predicting the data upwards of 100% for some cases). The data shows an increased tendency toward homogeneous flow as the pressure and flow rate are increased, and in fact the homogeneous model best predicts the bulk of the data at the highest pressure tested.« less
  • Effects of electrohydrodynamic (EHD) on the two-phase heat transfer enhancement and pressure drop of pure R-134a condensing inside a horizontal micro-fin tube are experimentally investigated. The test section is a 2.5m long counter flow tube-in-tube heat exchanger with refrigerant flowing in the inner tube and cooling water flowing in the annulus. The inner tube is made from micro-fin horizontal copper tubing of 9.52mm outer diameter. The electrode is made from cylindrical stainless steel of 1.47mm diameter. Positive high voltage is supplied to the electrode wire, with the micro-fin tube grounded. In the presence of the electrode, a maximum heat transfermore » enhancement of 1.15 is obtained at a heat flux of 10kW/m{sup 2}, mass flux of 200kg/m{sup 2}s and saturation temperature of 40{sup o}C, while the application of an EHD voltage of 2.5kV only slightly increases the pressure drop. New correlations of the experimental data based on the data gathered during this work for predicting the condensation heat transfer coefficients are proposed for practical application. (author)« less