Friction factor correlation and pressure loss of single-phase flow inside herringbone microfin tubes

2007 ◽  
Vol 30 (7) ◽  
pp. 1187-1194 ◽  
Author(s):  
Hasan M.M. Afroz ◽  
Akio Miyara
Keyword(s):  
Friction Factor ◽  
Pressure Loss ◽  
Single Phase ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Friction Factor Correlation ◽  
Microfin Tubes

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.

Measurement of Pressure Loss Throughout a Clogged Steam Generator Tube Support Plate in Single Phase Flow

2010 ◽  
Author(s):  
Olivier Brunin ◽  
Geoffrey Deotto ◽  
Franck David ◽  
Joe¨l Pillet ◽  
Gilles Dague ◽  
...  
Keyword(s):  
Pressure Loss ◽  
Single Phase ◽  
Experimental Approach ◽  
Two Phase Flow ◽  
Loss Coefficient ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Steam Generators ◽  
Two Phase ◽  
Pressure Loss Coefficient

After a period of several years of operation, steam generators can be affected by fouling and clogging. Fouling means that deposits of sludge accumulate on tubes or tube support plates (TSP). That results in a reduction of heat exchange capabilities and can be modelled by means of a fouling factor. Clogging is a reduction of flow free area due to an accumulation of sludge in the space between TSP and tubes. The increase of the clogging ratio results in an increase of the overall TSP pressure loss coefficient. The link between the clogging ratio and the overall TSP pressure loss coefficient is the most important aspect of our capability to accurately calculate the thermal-hydraulics of clogged steam generators. The aim of the paper is to detail the experimental approach chosen by EDF and AREVA NP to address the calculation uncertainties. The calculation method is classically based on the computation of a single-phase (liquid-only) pressure loss coefficient, which is multiplied by a two-phase flow factor. Both parameters are well documented and can be derived on the basis of state of the art methods such as IDEL’CIK diagrams and CHISHOLM formula. The experimental approach consists of a validation of the correlations by performing tests on a mock-up section with an upward flow throughout a vertical array of tubes. A mixture of water and vapour refrigerant R116 is used to represent two-phase flows. The tube bundle is composed of a 25 tubes array in a square arrangement. The overall height of the mock-up is 2 m. Eight test TSPs were manufactured, considering eight different clogging configurations: six plates with a typical clogging profile at six clogging ratios (0, 44%, 58%, 72%, 86%, 95%), and two plates with a clogging ratio of 72% associated with two different clogging profiles (large bending radius profile and rectangular profile). A series of tests were performed in 2009 in single-phase flow conditions. Two-phase flow tests with a mixture of liquid water and vapour refrigerant R116 will be performed in 2010. The paper illustrates the main results obtained during the single-phase tests performed in 2009.

An Experimental Study of Friction Factor in the Transition Region for Single Phase Flow in Mini- and Micro-Tubes

2008 ◽  
Author(s):  
Afshin J. Ghajar ◽  
Rahul P. Rao ◽  
Wendell L. Cook ◽  
Clement C. Tang
Keyword(s):  
Experimental Study ◽  
Friction Factor ◽  
Transition Region ◽  
Pressure Transducer ◽  
Single Phase ◽  
Tube Diameter ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Steel Tubes ◽  
Pressure Sensing

A systematic and accurate experimental investigation of friction factor in the transition region for single phase flow in mini- and micro-tubes has been performed for eight stainless steel tubes with diameters ranging from 2083 μm to 667 μm. The pressure drop measurements were carefully performed by paying particular attention to the sensitivity of the pressure-sensing diaphragms used in the pressure transducer. Experimental results indicated that the start and end of the transition region was influenced by varying the tube diameter. The friction factor profile was not significantly affected for the tube diameters between 2083 μm and 1372 μm. However, the influence of the tube diameter on the friction factor profile became noticeable as the diameter decreased from 1372 μm to 667 μm.

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.

Flow Structure and Pressure Loss for Two Phase Flow in Return Bends

1984 ◽  
Vol 106 (1) ◽  
pp. 30-37 ◽  
Author(s):  
K. Hoang ◽  
M. R. Davis
Keyword(s):  
Flow Structure ◽  
Pressure Loss ◽  
Single Phase ◽  
Velocity Slip ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Two Phase ◽  
Phase Loss ◽  
Loss Coefficients ◽  
Flow Effects

Experimental observations of flow structure and pressure loss have been made for froth flow within 180 deg circular pipe bends. Within the bend the distributions of pressure observed reflected the onset of rotation and phase separation effects, whilst secondary flow effects were apparent in the voidage distributions at outlet. Significant components of the overall pressure drop were found both within the bend itself and in the pipe immediately downstream of the bend. Velocity slip between gas and liquid was found to increase observed loss coefficients by approximately 10 percent. The overall loss coefficients were substantially larger than in single phase flow, particularly for bends with larger radius of centerline curvature where they increased by as much as five times the single phase value. The overall pressure loss coefficients were highest for the sharper radius bends, and it was deduced that flow separation and remixing contributed mainly to the increase over single phase loss coefficients.

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.

Sign in / Sign up

Export Citation Format

Share Document