A numerical investigation on single-phase flow characteristics and frictional pressure drop in helical pipes

2020 ◽  
Vol 52 (4) ◽  
pp. 045505
Author(s):  
Pengxin Cheng ◽  
Nan Gui ◽  
Xingtuan Yang ◽  
Jiyuan Tu ◽  
Shengyao Jiang ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Numerical Investigation ◽  
Single Phase ◽  
Flow Characteristics ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Frictional Pressure Drop

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

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Zan Wu ◽  
Bengt Sundén
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Single Phase ◽  
Flow Boiling ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Frictional Pressure Drop ◽  
Friction Factors ◽  
Flow Condensation ◽  
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.

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

2014 ◽  
Author(s):  
Zan Wu ◽  
Bengt Sundén
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Single Phase ◽  
Flow Boiling ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Frictional Pressure Drop ◽  
Friction Factors ◽  
Flow Condensation ◽  
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, respectively. 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.

scholarly journals PREDICTION OF PRESSURE DROP IN HELICAL COIL WITH SINGLE PHASE FLOW OF NON-NEWTONIAN FLUID

2012 ◽  
pp. 256-261
Author(s):  
B.S.V.S.R. KRISHNA
Keyword(s):  
Pressure Drop ◽  
Single Phase ◽  
Methyl Cellulose ◽  
Helix Angle ◽  
Helical Coil ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Number Range ◽  
Frictional Pressure Drop ◽  
Carboxy Methyl

The pressure drop of single phase was studied experimentally with non-Newtonian fluids of Carboxy Methyl Cellulose (CMC). Single helical coil with five different helix angles were used in this study to identify the effect of helix angle on pressure drop. The effect of helix angle is significant in moderate and high generalized Dean’s number of laminar region. The effect is insignificant in low generalized Dean’s number range and turbulent region. Correlations were developed for predicting the frictional pressure drop in laminar and turbulent regions.

Two-Phase Flow Behavior in Channels With Sudden Area Change Using Experimental and Computational Approach

2017 ◽  
Author(s):  
Ashish Kotwal ◽  
Che-Hao Yang ◽  
Clement Tang
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Experimental Analysis ◽  
Single Phase ◽  
Computational Analysis ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Two Phase ◽  
Flow Rates ◽  
Area Change

The current study shows computational and experimental analysis of multiphase flows (gas-liquid two-phase flow) in channels with sudden area change. Four test sections used for sudden contraction and expansion of area in experiments and computational analysis. These are 0.5–0.375, 0.5–0.315, 0.5–0.19, 0.5–0.14, inversely true for expansion channels. Liquid Flow rates ranging from 0.005 kg/s to 0.03 kg/s employed, while gas flow rates ranging from 0.00049 kg/s to 0.029 kg/s implemented. First, single-phase flow consists of only water, and second two-phase Nitrogen-Water mixture flow analyzed experimentally and computationally. For Single-phase flow, two mathematical models used for comparison: the two transport equations k-epsilon turbulence model (K-Epsilon), and the five transport equations Reynolds stress turbulence interaction model (RSM). A Eulerian-Eulerian multiphase approach and the RSM mathematical model developed for two-phase gas-liquid flows based on current experimental data. As area changes, the pressure drop observed, which is directly proportional to the Reynolds number. The computational analysis can show precise prediction and a good agreement with experimental data when area ratio and pressure differences are smaller for laminar and turbulent flows in circular geometries. During two-phase flows, the pressure drop generated shows reasonable dependence on void fraction parameter, regardless of numerical analysis and experimental analysis.

Two-Phase Flow Through Square and Circular Microchannels—Effects of Channel Geometry

2004 ◽  
Vol 126 (4) ◽  
pp. 546-552 ◽  
Author(s):  
Peter M.-Y. Chung ◽  
Masahiro Kawaji ◽  
Akimaro Kawahara ◽  
Yuichi Shibata
Keyword(s):  
Pressure Drop ◽  
Void Fraction ◽  
Two Phase Flow ◽  
Flow Characteristics ◽  
Separated Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Channel Geometry ◽  
Frictional Pressure Drop ◽  
Channel Shape

An adiabatic experiment was conducted to investigate the effect of channel geometry on gas-liquid two-phase flow characteristics in horizontal microchannels. A water-nitrogen gas mixture was pumped through a 96 μm square microchannel and the resulting flow pattern, void fraction and frictional pressure drop data were compared with those previously reported by the authors for a 100 μm circular microchannel. The pressure drop data were best estimated using a separated-flow model and the void fraction increased non-linearly with volumetric quality, regardless of the channel shape. However, the flow maps exhibited transition boundaries that were shifted depending on the channel shape.

An Experimental Investigation of Gas-Liquid Heat Transfer in Rectangular Micro-Channels

2013 ◽  
Author(s):  
Sira Saisorn ◽  
Somchai Wongwises ◽  
Piyawat Kuaseng ◽  
Chompunut Nuibutr ◽  
Wattana Chanphan
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Flow Direction ◽  
Flow Characteristics ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Two Phase ◽  
Camera System ◽  
Micro Channels ◽  
Flow Mechanisms

The investigations of heat transfer and fluid flow characteristics of non-boiling air-water flow in micro-channels are experimentally studied. The gas-liquid mixture from y-shape mixer is forced to flow in the 21 parallel rectangular microchannels with 40 mm long in the flow direction. Each channel has a width and a depth of 0.45 and 0.41 mm, respectively. Flow visualization is feasible by incorporating the stereozoom microscope into the camera system and different flow patterns are recorded. The experiments are performed under low superficial velocities. Two-phase heat transfer gives better results when compared with the single-phase flow. It is found from the experiment that heat transfer enhancement up to 53% is obtained over the single-phase flow. Also, the change in the configuration of the inlet plenum can result in the different two-phase flow mechanisms.

Single-Phase Flow Characteristics and Effect of Dissolved Gases on Heat Transfer Near Saturation Conditions in Microchannels

2002 ◽  
Author(s):  
Satish G. Kandlikar ◽  
Mark E. Steinke ◽  
Prabhu Balasubramanian
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Surface Temperature ◽  
Friction Factor ◽  
Single Phase ◽  
Saturation Temperature ◽  
Slight Reduction ◽  
Phase Flow ◽  
Dissolved Gases ◽  
Single Phase Flow

An experimental investigation is carried out to study the heat transfer and pressure drop in the single-phase flow of water in a microchannel. The effect of dissolved gases on heat transfer and pressure drop is studied as the wall temperature approaches the saturation temperature of water, causing air and water vapor mixture to form bubbles on the heater surface. A set of six parallel microchannels, each approximately 200 micrometers square in cross section and fabricated in copper, with a hydraulic diameter of 207 micrometers, is used as the test section. Starting with air-saturated water at atmospheric pressure and temperature, the air content in the water is varied by vigorously boiling the water at elevated saturation pressures to provide different levels of dissolved air concentrations. The single-phase friction factor and heat transfer results are presented and compared with the available theoretical values. The friction factors for adiabatic cases match closely with the laminar single-phase friction factor predictions available for conventional-sized channels. The diabatic friction factor, after applying the correction for temperature dependent properties, also agrees well with the theoretical predictions. The Nusselt numbers, after applying the property corrections, are found to be below the theoretical values available in literature for constant temperature heating on all four sides. The disagreement is believed to be due to the three-sided heating employed in the current experiments. The effect of gas content on the heat transfer for the three gas concentrations is investigated. Nucleation was observed at a surface temperature of 90.5°C, for the reference case of 8.0 ppm. For the degassed cases (5.4 ppm and 1.8 ppm), nucleation is not observed until the surface temperature reached close to 100°C. An increase in heat transfer coefficient for surface temperatures above saturation is observed. However, a slight reduction in heat transfer is noted as the bubbles begin to nucleate. The presence of an attached bubble layer on the heating surface is believed to be responsible for this effect.

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