scholarly journals Corrigendum to “Pressure drop and flow patterns of boiling flows in Mini-channels with Semi-Circular Cross-Section” [Appl. Therm. Eng. 194 (2021) 117096]

2022 ◽  
Vol 205 ◽  
pp. 118091
Author(s):  
Yohei Kubo ◽  
Sayaka Yamada ◽  
Hideki Murakawa ◽  
Hitoshi Asano
Keyword(s):  
Pressure Drop ◽  
Cross Section ◽  
Circular Cross Section ◽  
Flow Patterns ◽  
Mini Channels

Experimental Investigation on Pressure Drop in Corrugated Pipes

2013 ◽  
Author(s):  
Hojin Ahn ◽  
Ibrahim Uslu
Keyword(s):  
Pressure Drop ◽  
Friction Factor ◽  
Cross Section ◽  
Circular Cross Section ◽  
Control Valve ◽  
Experimental Result ◽  
Helical Coil ◽  
Solar Panels ◽  
Steel Pipes ◽  
Friction Factors

The characteristics of pressure drop in corrugated pipes were experimentally studied in both straight and helically coiled configurations. The present study employed the stainless-steel pipes with the corrugation of circular cross section, which are widely used in boilers and pipe systems between solar panels and boilers. The diameters of corrugated pipes were 20.4, 25.4, 34.5 and 40.5 mm. The corrugated pipe, approximately 10 m in length, was configured either in the straight manner or in the helical coil with the helix diameter of 0.43 or 0.64 m. Water stored in a tank was fed into a corrugated pipe by a pump while the flow rate was controlled by a control valve. The friction factors of the pipes remain constant over the range of Reynolds number from 4,000 to 50,000, indicating that the flow in the pipe was fully turbulent. When the pipe was straightly configured, the friction factors were measured to be 0.070, 0.075, 0.12 and 0.22 for the diameter of 20.4, 25.4, 34.5 and 40.5 mm, respectively. Thus the present study showed that the friction factors increased with the increasing diameter of the pipe. This result is clearly contrary to a rare experimental result available in the literature. On the other hand, as expected, the friction factor for the helically coiled configuration was higher than that of the straight configuration with the same tube diameter, and the configuration of the smaller helix diameter yielded the larger friction factor. The reason for the increasing friction factor with the increasing pipe diameter remains to be explored further.

Flow Boiling of Carbon Dioxide in Horizontal Mini-Channel and Pattern Dynamics Approach to Study Flow Pattern

2009 ◽  
Author(s):  
Mamoru Ozawa
Keyword(s):  
Carbon Dioxide ◽  
High Pressure ◽  
Pressure Drop ◽  
Flow Pattern ◽  
Flow Instability ◽  
Flow Boiling ◽  
Flow Patterns ◽  
Bond Number ◽  
Pattern Dynamics ◽  
Mini Channels

This paper provides a brief review on experimental and numerical investigations of flow patterns, pressure drop, and heat transfer including critical heat flux (CHF) of flow boiling carbon-dioxide (CO2) at high pressure in mini-channels ranging 0.5mm to 3.0mm in diameter. The flow patterns of CO2 at high pressure with small density difference between vapor and liquid and low surface tension show a slightly different structure from so far observed in mini-channels with air and water. The phase mal-distribution, similar to conventional tubes, in the cross-section becomes rather significant beyond the critical Bond number, which leads to the intermittent dryout at the upper wall of the tube. So far proposed flow pattern transition criteria are ineffective there, and newly developed discrete bubble model demonstrates its high potential in predicting flow patterns. Conventional homogeneous flow model is still available in predicting pressure drop. Based on this fact, flow instability problems, which significantly affect CHF, is discussed focusing on high-pressure CO2 flow.

Experimental Study and Numerical Analysis of Water Single-Phase Pressure Drop Across an Array of Circular Micro-Pin-Fins

2011 ◽  
Author(s):  
Jonathan R. Mita ◽  
Weilin Qu ◽  
Marcelo H. Kobayashi ◽  
Frank E. Pfefferkorn
Keyword(s):  
Numerical Analysis ◽  
Pressure Drop ◽  
Cross Section ◽  
Single Phase ◽  
Three Dimensional ◽  
Circular Cross Section ◽  
Experimental Results ◽  
Inlet Temperature ◽  
Pin Fins ◽  
Micro Pin Fins

This study investigates pressure drop associated with water liquid single-phase flow across an array of staggered micro-pin-fins having circular cross-section. The micro-pin-fins are micro-end milled out of oxygen free copper and have the following dimensions: 180 micron diameter and 683 micron height. The longitudinal pitch and transverse pitch are equal to 400 microns. Seven water inlet temperatures from 22 to 80 °C, and seventeen maximum mass velocities for each inlet temperature, ranging from 159 to 1475 kg/m2s, were tested. The test module was well insulated to maintain adiabatic conditions. The experimental results were compared to those from a micro-pin-fin array having similar size and geometrical arrangement but a square cross-section. The circular micro-pin-fins were seen to yield a significantly lower pressure drop than the square micro-pin-fins. The present experimental results were also compared with the predictions of several friction factor correlations as well as the results from a three-dimensional numerical analysis. Neither was able to accurately predict the experimental data.

Two-Phase Flow (Oil and Water) in Ducts with the Elliptical Cross-Section: Modeling and Simulation

2019 ◽  
Vol 24 ◽  
pp. 61-75
Author(s):  
J.L. de Oliveira ◽  
A.G. Barbosa de Lima ◽  
R. Pereira Ramos ◽  
H. Luma Fernandes Magalhães ◽  
W.R. Gomes dos Santos ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Aspect Ratio ◽  
Cross Section ◽  
Operating Cost ◽  
Circular Cross Section ◽  
Elliptical Cross Section ◽  
Two Phase ◽  
Elliptical Cross ◽  
Ansys Cfx ◽  
Velocity Pressure

In the oil industry, pipelines (circular ducts) are widely used for the transportation of oil and yours derived. Because of their advantages, such as low operating cost and increased safety during transportation, pipelines have become indispensable for transporting oil in large quantities and for long distances. As an alternative to this problem, the transport of oil and water can be accomplished using ducts with an elliptical cross-section. Thus, this work has the objective of studying the flow of oil and water in cylindrical ducts with an elliptical cross-section by using the Ansys CFX software. Results of the velocity, pressure and volumetric fraction distributions of the oil and water phases are presented and analyzed. By applying the same inlet velocity to oil and water, revealed that the elliptical duct, with aspect ratio equal to 5.0, has a pressure drop less (84.2%) than the pressure drop obtained for one duct of circular cross-section (aspect ratio equal to 1.0).

Numerical investigation of the effect of water/Al2O3 nanofluid on heat transfer in trapezoidal, sinusoidal and stepped microchannels

2019 ◽  
Vol 30 (5) ◽  
pp. 2439-2465 ◽  
Author(s):  
Vahid Jaferian ◽  
Davood Toghraie ◽  
Farzad Pourfattah ◽  
Omid Ali Akbari ◽  
Pouyan Talebizadehsardari
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Cross Section ◽  
Cross Sections ◽  
Volume Fraction ◽  
Pure Water ◽  
Circular Cross Section ◽  
Reynolds Numbers ◽  
Two Phase ◽  
Content Type

Purpose The purpose of this study is three-dimensional flow and heat transfer investigation of water/Al2O3 nanofluid inside a microchannel with different cross-sections in two-phase mode. Design/methodology/approach The effect of microchannel walls geometry (trapezoidal, sinusoidal and stepped microchannels) on flow characteristics and also changing circular cross section to trapezoidal cross section in laminar flow at Reynolds numbers of 50, 100, 300 and 600 were investigated. In this study, two-phase water/Al2O3 nanofluid is simulated by the mixture model, and the effect of volume fraction of nanoparticles on performance evaluation criterion (PEC) is studied. The accuracy of obtained results was compared with the experimental and numerical results of other similar papers. Findings Results show that in flow at lower Reynolds numbers, sinusoidal walls create a pressure drop in pure water flow which improves heat transfer to obtain PEC < 1. However, in sinusoidal and stepped microchannel with higher Reynolds numbers, PEC > 1. Results showed that the stepped microchannel had higher pressure drop, better thermal performance and higher PEC than other microchannels. Originality/value Review of previous studies showed that existing papers have not compared and investigated nanofluid in a two-phase mode in inhomogeneous circular, stepped and sinusoidal cross and trapezoidal cross-sections by considering the effect of changing channel shape, which is the aim of the present paper.

A General Model for Predicting Low Reynolds Number Flow Pressure Drop in Non-Uniform Microchannels of Non-Circular Cross Section in Continuum and Slip-Flow Regimes

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
M. Akbari ◽  
A. Tamayol ◽  
M. Bahrami
Keyword(s):  
Pressure Drop ◽  
Cross Section ◽  
General Model ◽  
Circular Cross Section ◽  
Numerical Data ◽  
Creeping Flow ◽  
Geometrical Parameters ◽  
Cross Sectional ◽  
Flow Pressure ◽  
The Cross

A general model that predicts single-phase creeping flow pressure drop in microchannels of a noncircular cross section under slip and no-slip regimes is proposed. The model accounts for gradual variations in the cross section and relates the pressure drop to geometrical parameters of the cross section, i.e., area, perimeter, and polar moment of inertia. The accuracy of the proposed model is assessed by comparing the results against experimental and numerical data collected from various studies in the literature for a wide variety of cross-sectional shapes. The suggested model can be used for the design and optimization of microsystems that contain networks of microchannels with noncircular cross sections resulting from different fabrication techniques.

Heat Transfer and Pressure Loss in a Two-Pass, Rectangular Channel Featuring a Reduced Cross-Sectional Area After the 180-Degree Tip Turn With Different Turning Vane Configurations

2020 ◽  
Author(s):  
Sulaiman M. Alsaleem ◽  
Lesley M. Wright ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Cross Section ◽  
Pressure Loss ◽  
Circular Cross Section ◽  
Sectional Area ◽  
Cross Sectional ◽  
Number Range

Abstract Serpentine, varying aspect ratio cooling passages, are typically used in cooling advanced gas turbine blades. These passages are usually connected by sharp, 180-deg bends. In the open literature, most of the internal cooling studies use a fixed cross-sectional area for multi-pass channels. Studies that use varying aspect ratio channels, along with a guide (turn) vane to direct the flow with turning, are scarce. In general, studies show that the incorporation of turning vanes in the bend region of a multi-pass channel keeps the heat transfer rate high while reducing pressure loss. Therefore, the current study investigates the effect of using different guide (turn) vane designs on both the detailed heat transfer distribution and pressure loss in a multi-pass channel with an aspect ratio of (4:1) in the entry passage and (2:1) in the second passage downstream of the vane (s). The first vane configuration is one solid-vane with a semi-circular cross-section connecting the two flow passages. The second configuration has three broken-vanes with a quarter-circular cross-section; two broken vanes are located downstream in the first passage (entering the turn), and one broken vane is upstream in the second passage (exiting the turn). For a Reynolds number range 15,000 to 45,000, detailed heat transfer distributions were obtained on all surfaces within the flow passages by using a transient liquid crystal method. The results show that the turning vane configurations have large effects on the heat transfer, in the turning bend and second passage, and the overall pressure drop. Results show that including the semi-circular vane in the turning region of a multi-pass channel enhanced the overall heat transfer by around 29% with a reduction in pressure loss by around 20%. Moreover, results show that the quarter-circular vane design provides higher overall averaged heat transfer enhancement than the semi-circular vane design by around 9% with penalty of higher pressure drop by 6%, which yields higher thermal performance by 7%, over the Reynolds number range.

Correlation of Adiabatic Two-Phase Pressure Drop Data Using the Frictional Law of Corresponding States

1993 ◽  
Vol 115 (2) ◽  
pp. 317-323 ◽  
Author(s):  
N. T. Obot ◽  
M. W. Wambsganss ◽  
D. M. France ◽  
J. A. Jendrzejczyk
Keyword(s):  
Pressure Drop ◽  
Cross Section ◽  
Total Mass ◽  
Single Phase ◽  
Circular Cross Section ◽  
Single Phase Flow ◽  
Two Phase ◽  
Frictional Pressure Drop ◽  
Law Of Corresponding States ◽  
Total Mass Flux

A method, based on that developed for single-phase flow, is proposed for the correlation of two-phase frictional pressure drop data. It is validated using air-water data obtained on small horizontal passages of rectangular and circular cross-section for values of total mass flux G in the 50-2000 kg/m2s range. The pressure drop for air-water mixtures can be predicted from the proposed correlations provided the critical quality (or superficial gas Reynolds number) and the critical pressure gradient for transition from bubble/plug-to-slug flow are known. A comparison of the proposed method with that of Lockhart and Martinelli is presented and discussed.

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