EFFECT OF AMBIENT TEMPERATURE VARIATION ON PRESSURE DROP DURING CONDENSATION IN LONG INCLINED TUBES

2021 ◽  
pp. 1-24
Author(s):  
Kaipo Kekaula ◽  
Yitung Chen
Keyword(s):  
Pressure Drop ◽  
Ambient Temperature ◽  
Two Phase ◽  
Temperature Changes ◽  
Ambient Temperatures ◽  
Frictional Pressure Drop ◽  
Wide Range ◽  
Data Points ◽  
Fan Speed ◽  
Increasing Temperature

Abstract Two-phase flow pressure drop during condensation of steam inside inclined tube heat exchangers was investigated over a wide range of ambient temperature. The ambient temperature changes from 3 to 45°C, the steam mass flux varies from 3 to 18 kg/(m2·s), vapor quality ranges from 0.51 to 0.86. 608 data points were experimentally obtained and compared with 8 commonly used correlations from the available literatures. Frictional pressure drop increases with increasing temperature difference and fan speed. For the full experimental dataset, the best overall performing correlation was obtained by using the Wallis correlation (MAPE = 17.60%, NRMSE = 14.87%). For cold ambient temperatures, (Tamb < 20°C, N=298), the best overall performing correlation was obtained by using the Carey correlation (MAPE = 11.02%, NRMSE = 14.71%). For hot ambient temperatures (Tamb >30°C, N = 196), the Lockhart and Martinelli correlation has shown the best performance (MAPE = 16.84%, NRMSE = 20.45%). An improved two-phase frictional pressure drop correlation based on the Wallis correlation [21] is proposed.

An Improved Correlation for Two-Phase Frictional Pressure Drop in Boiling and Adiabatic Downflow in the Annular Flow Regime

1991 ◽  
Vol 205 (5) ◽  
pp. 317-328 ◽  
Author(s):  
J F Klausner ◽  
B T Chao ◽  
S L Soo
Keyword(s):  
Pressure Drop ◽  
Film Thickness ◽  
Flow Regime ◽  
Annular Flow ◽  
Volume Fraction ◽  
Interfacial Shear Stress ◽  
Published Data ◽  
Two Phase ◽  
Frictional Pressure Drop ◽  
Wide Range

An improved correlation is presented for annular two-phase frictional pressure drop data for vertical downflow. An ideal dimensionless film thickness based on the vapour volume fraction, a characteristic friction factor based on the two-phase frictional pressure gradient and a Weber number relevant for the interfacial capillary wave structure are the correlating parameters. The proposed new correlating scheme is tested against a wide range of data obtained in this investigation for refrigerant R11 in forced convection boiling and in adiabatic test sections of 19 mm cylindrical cross-section as well as published data for air-water and air-glycerine solution mixtures in the annular flow regime. Over 80 per cent of the measured values fall within ±30 per cent of those predicted from the correlation. Due to the wide range of liquid film thickness covered, 0.05–2.9 mm, its validity extends past the range where previously reported downflow pressure drop correlations fail. A paradox connected with previously reported annular downflow pressure drop correlations based on the liquid-vapour interfacial shear stress is pointed out. Upflow frictional pressure drop data in the annular flow regime can also be correlated by the proposed scheme.

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.

A General Correlation for Frictional Pressure Drop of Flow Boiling in Plate Heat Exchangers

2020 ◽  
Author(s):  
Weiyu Tang ◽  
Tong Lv ◽  
Boren Zheng ◽  
Wei Li
Keyword(s):  
Pressure Drop ◽  
Heat Exchangers ◽  
Flow Boiling ◽  
Saturation Pressure ◽  
Influence Factors ◽  
Two Phase ◽  
Plate Heat ◽  
General Correlation ◽  
Frictional Pressure Drop ◽  
Data Points

Abstract Plate heat exchangers are widely used in various industries for many years. The corrugated channels on the plates effectively enhance the turbulence of flow boiling and complicate the prediction of pressure drop. This paper presents a brief review about the influence factors of frictional pressure drop during flow boiling in plate heat exchangers. Experimental data points of frictional pressure drop were collected from previous literatures to develop a general correlation. The database contained 454 data points, covering eight refrigerants, mass flux range 5.5–137 kg m-2 s-1, heat flux 0–30 kW m-2, vapor quality 0.07–0.95, saturation pressure 0.11–2.7 MPa, chevron angle 30°–70° and hydraulic diameter 1.7–5.4 mm. In this work, several existing correlations were compared with the database, and all of them seem fail to give an acceptable prediction. A new correlation was proposed with multiple regression analysis in terms of two-phase Fanning friction factor. The new method showed good agreement and predicted 63.2% and 92.9% of data points within ±30% and ±50% errors, respectively.

Two-Phase Flow Regime Modeling and Pressure Drop Behavior

2007 ◽  
Author(s):  
Braden A. McDermott ◽  
Timothy A. Shedd
Keyword(s):  
Pressure Drop ◽  
Flow Regime ◽  
Two Phase Flow ◽  
Current Data ◽  
Phase Flow ◽  
Two Phase ◽  
Frictional Pressure Drop ◽  
Flow Maps ◽  
Mass Fluxes ◽  
Wide Range

A unique horizontal two-phase flow facility has been fabricated in an effort to understand the dynamics of two-phase flow in small pipes. The fluid chosen for study is the low pressure refrigerant R-123. In this work, two-phase pressure drop data were obtained for two-phase flow of refrigerant R-123 in a 17.0 mm inner diameter tube over a wide range of quality, from .015–1, and mass fluxes that were varied from 50 kg m−2 s−1 to 550 kg m−2 s−1. These data have been compared, as a whole and by regime, against four frequently-used two-phase frictional pressure drop prediction correlations. Flow regimes were visualized using a quartz tube at the end of the test section over this wide range of conditions, which ranged from stratified to annular flow. Each condition was mapped on the Mandhane, Taitel-Dukler, and Kattan-Favrat-Thome flow regime maps in an attempt to understand the applicability of each. Some discrepancies exist between the current data and the published flow maps, and recommendations are made based on these observations. The pressure drop data appear to be dependent upon the flow regime, suggesting that an entire set of correlations is necessary based upon flow regime for accurate prediction of pressure drop.

Analysis of Flow Boiling Frictional Pressure Drop in Plate Heat Exchangers

2020 ◽  
Vol 13 (3) ◽  
Author(s):  
Weiyu Tang ◽  
Tong Lv ◽  
Wei Li ◽  
S. A. Sherif ◽  
Zahid Ayub ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Heat Exchangers ◽  
Flow Boiling ◽  
Saturation Temperature ◽  
Two Phase ◽  
Plate Heat ◽  
Frictional Pressure Drop ◽  
Data Points ◽  
Geometrical Factors ◽  
Fanning Friction Factor

Abstract Plate heat exchangers are widely used in various industries for many years. The corrugated channels on the plates effectively enhance the turbulence of flow boiling and complicate the prediction of pressure drop. This article presents a brief review about effects of various operating and geometrical factors on frictional pressure drop during flow boiling in plate heat exchangers. Experimental data points of frictional pressure drop were collected from the previous literature to develop a general correlation. The database contained 591 data points, covering six different refrigerants, mass flux range 5.5–130 kg/m2/s1, heat flux 0–15 kW/m2, vapor quality 0.04–0.96, saturation temperature −25 to 61 C°, chevron angle 20 deg–65 deg, and hydraulic diameter 1.7–5.35 mm. In this study, several existing correlations were compared with the database, and most of them seem fail to give an acceptable prediction. A new correlation was proposed with multiple regression analysis in terms of two-phase Fanning friction factor. The new method showed a good agreement with the present database and predicted 70.2% and 91.7% of data points within ±30% and ±50% errors, respectively.

Ambient temperature effects on physiological traits of white-tailed deer

1975 ◽  
Vol 53 (6) ◽  
pp. 679-685 ◽  
Author(s):  
J. B. Holter ◽  
W. E. Urban Jr. ◽  
H. H. Hayes ◽  
H. Silver ◽  
H. R. Skutt
Keyword(s):  
Heart Rate ◽  
Body Temperature ◽  
Energy Expenditure ◽  
Ambient Temperature ◽  
Temperature Effects ◽  
Temperature Changes ◽  
Wind Chill ◽  
Ambient Temperatures ◽  
Energy Equilibrium ◽  
Body Energy

Six adult white-tailed deer (Odocoileus virginianus borealis) were exposed to 165 periods of 12 consecutive hours of controlled constant ambient temperature in an indirect respiration calorimeter. Temperatures among periods varied from 38 to 0 (summer) or to −20C (fall, winter, spring). Traits measured were energy expenditure (metabolic rate), proportion of time spent standing, heart rate, and body temperature, the latter two using telemetry. The deer used body posture extensively as a means of maintaining body energy equilibrium. Energy expenditure was increased at low ambient temperature to combat cold and to maintain relatively constant body temperature. Changes in heart rate paralleled changes in energy expenditure. In a limited number of comparisons, slight wind chill was combatted through behavioral means with no effect on energy expenditure. The reaction of deer to varying ambient temperatures was not the same in all seasons of the year.

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.

Effect of Tube Diameter on Flow Phenomena of Gas-Liquid Two-Phase Flow in Microchannels

2015 ◽  
Author(s):  
Hideo Ide ◽  
Eiji Kinoshita ◽  
Ryo Kuroshima ◽  
Takeshi Ohtaka ◽  
Yuichi Shibata ◽  
...  
Keyword(s):  
Pressure Drop ◽  
High Speed ◽  
Water Solution ◽  
Flow Direction ◽  
Flow Characteristics ◽  
Tube Diameter ◽  
Two Phase ◽  
Frictional Pressure Drop ◽  
Flow Phenomena ◽  
The Waves

Gas-liquid two-phase flows in minichannels and microchannels display a unique flow pattern called ring film flow, in which stable waves of relatively large amplitudes appear at seemingly regular intervals and propagate in the flow direction. In the present work, the velocity characteristics of gas slugs, ring films, and their features such as the gas slug length, flow phenomena and frictional pressure drop for nitrogen-distilled water and nitrogen-30 wt% ethanol water solution have been investigated experimentally. Four kinds of circular microchannels with diameters of 100 μm, 150 μm, 250 μm and 518 μm were used. The effects of tube diameter and physical properties, especially the surface tension and liquid viscosity, on the flow patterns, gas slug length and the two-phase frictional pressure drop have been investigated by using a high speed camera at 6,000 frames per second. The flow characteristics of gas slugs, liquid slugs and the waves of ring film are presented in this paper.

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