Drag Reduction for Nanobubble Mixture Flows Through Micro-Apertures

Drag reduction effect for microbubble mixtures flows has been investigated and reported. However, few studies have focused on nanobubble mixtures, which have sub-micron meter size fine bubbles. In the present study, nanobubble mixtures for water and glycerol solution were passed through several sizes of micro-apertures, and the resultant pressure drops, as compared with water and glycerol solution alone, were evaluated. For small apertures, the experimentally measured pressure drop was less than that for water and glycerol alone. This phenomenon is considered in terms of interface behavior and attributed to the electric interaction between an electric double layer and fine bubbles. The results of the present study suggest that the addition of nanobubbles to a liquid results in excellent drag reduction.

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Measurement of Pressure Drop in a Liquid Metal Reactor Fuel Assembly

Thermal Hydraulic Problems, Sloshing Phenomena, and Extreme Loads on Structures ◽

10.1115/pvp2002-1135 ◽

2002 ◽

Cited By ~ 1

Author(s):

Seok Ki Choi ◽

Il Kon Choi ◽

Kil Yong Lee ◽

Ho Yun Nam ◽

Jong Hyeun Choi ◽

...

Keyword(s):

Experimental Data ◽

Pressure Drop ◽

Liquid Metal ◽

Fuel Assembly ◽

Diameter Ratio ◽

Pressure Drops ◽

Liquid Metal Reactor ◽

The Wire ◽

Measured Pressure ◽

Reactor Fuel Assembly

An experimental study has been carried out to measure the pressure drop in a 271-pin fuel assembly of a liquid metal reactor. The rod pitch to rod diameter ratio (P/D) of the fuel assembly is 1.2 and the wire lead length to rod diameter ratio (H/D) is 24.84. Measurements are made for five different sections in a fuel assembly; inlet orifice, fuel assembly inlet, wire-wrapped fuel assembly, fuel assembly outlet and fuel assembly upper region. A series of water experiments have been conducted changing flow rate and water temperature. It is shown that the pressure drops in the inlet orifice and in the wire-wrapped fuel assembly are much larger than those in other regions. The measured pressure drop data in a wire-wrapped fuel assembly region is compared with the existing four correlations. It is shown that the correlation proposed by Cheng and Todreas fits the best with the present experimental data among the four correlations considered.

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Effect of Viscosity on the Pressure Gradient in 4-Inch Pipe

Volume 7: Fluids Engineering Systems and Technologies ◽

10.1115/imece2014-37918 ◽

2014 ◽

Author(s):

M. Mudasar Imam ◽

Mehaboob Basha ◽

S. M. Shaahid ◽

Aftab Ahmad ◽

Luai M. Al-Hadhrami

Keyword(s):

Pressure Drop ◽

Liquid Velocity ◽

Pressure Drops ◽

Increase With Increase ◽

Empirical Relations ◽

Inclination Angles ◽

The Difference ◽

Reference Pressure ◽

Velocity Pressure ◽

Measured Pressure

The pressure drop of liquids of different viscosities in multiphase flow is still a subject of research. This paper presents pressure drop measurements of water and oil single phase flow in horizontal and inclined 4 inch diameter stainless steel pipe at different flow rates. Potable water and Exxol D80 oil were used in the study. Experiments were carried out for different inclination angles including; 0°, 15°, 30° (upward and downward flows). Inlet liquid velocities were varied from 0.4 to 1.2 m/s and reference pressure was set at 1 bar. Water and Oil viscosities are 0.798 Pa.s and 1.56 Pa.s at 30°C, respectively. Pressure drop has been found to increase with increase in liquid velocity. Pressure drop has been observed to increase asymptotically with pipe inclination. Upward flows are associated with high pressure drop as compared to downward flows. The pressure drop of water is greater than that of oil for all inclinations. This difference can be attributed to the difference in fluid viscosities and densities. Measured pressure drops were compared with existing empirical relations and good agreement was noticed.

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Predicted and Measured Pressure Drop in Parallel Plate Rotary Regenerators

Journal of Fluids Engineering ◽

10.1115/1.3240625 ◽

1980 ◽

Vol 102 (1) ◽

pp. 59-63 ◽

Cited By ~ 3

Author(s):

I. L. Maclaine-Cross ◽

C. W. Ambrose

Keyword(s):

Mass Transfer ◽

Pressure Drop ◽

Cross Section ◽

Heat Exchangers ◽

Parallel Plate ◽

Sensible Heat ◽

Pressure Drops ◽

Flow Acceleration ◽

Outlet Pressure ◽

Measured Pressure

The flow in the passages of parallel plate rotary heat exchangers or regenerators is laminar and fully developed. Laminar flow theory should allow an accurate prediction of heat and mass transfer and pressure drop. Previously measured values of pressure drop have been 20 percent higher than predicted. Pressure drop is predicted here by considering the passage cross section rectangular and correcting for flow acceleration, property variations, and inlet and outlet pressure drop. The pressure drops measured on a parallel plate sensible heat regenerator were within 3 percent of theory and on a prototype parallel plate total heat regenerator within 4 percent.

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Measurement of Pressure Drop in a Full-Scale Fuel Assembly of a Liquid Metal Reactor

Journal of Pressure Vessel Technology ◽

10.1115/1.1565076 ◽

2003 ◽

Vol 125 (2) ◽

pp. 233-238 ◽

Cited By ~ 26

Author(s):

Seok Ki Choi ◽

Il Kon Choi ◽

Ho Yun Nam ◽

Jong Hyeun Choi ◽

Hoon Ki Choi

Keyword(s):

Experimental Data ◽

Experimental Study ◽

Pressure Drop ◽

Liquid Metal ◽

Fuel Assembly ◽

Diameter Ratio ◽

Pressure Drops ◽

Liquid Metal Reactor ◽

The Wire ◽

Measured Pressure

An experimental study has been carried out to measure the pressure drop in a 271-pin fuel assembly of a liquid metal reactor. The rod pitch to rod diameter ratio P/D of the fuel assembly is 1.2 and the wire lead length to rod diameter ratio H/D is 24.84. Measurements are made for five different sections in a fuel assembly; inlet orifice, fuel assembly inlet, wire-wrapped fuel assembly, fuel assembly outlet and fuel assembly upper region. A series of water experiments have been conducted changing flow rate and water temperature. It is shown that the pressure drops in the inlet orifice and in the wire-wrapped fuel assembly are much larger than those in other regions. The measured pressure drop data in a wire-wrapped fuel assembly region is compared with the existing four correlations. It is shown that the correlation proposed by Cheng and Todreas fits best with the present experimental data among the four correlations considered.

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Two-Phase Pressure Drop in the Intermittent Flow Regime for Noncircular Microchannels

Heat Transfer, Volume 4 ◽

10.1115/imece2002-39194 ◽

2002 ◽

Cited By ~ 2

Author(s):

Srinivas Garimella ◽

Jesse D. Killion ◽

John W. Coleman

Keyword(s):

Pressure Drop ◽

Flow Regime ◽

Intermittent Flow ◽

Average Error ◽

Two Phase ◽

Pressure Drops ◽

Mass Fluxes ◽

Tube Shape ◽

Measured Pressure ◽

Phase Pressure

This paper reports the development of an experimentally validated model for pressure drop during intermittent flow of condensing refrigerant R134a in horizontal, noncircular microchannels. Two-phase pressure drops were measured in six noncircular channels ranging in hydraulic diameter from 0.42 mm to 0.84 mm. The tube shapes included square, rectangular, triangular, barrel-shaped, and others. For each tube under consideration, pressure drop measurements were taken over the entire range of qualities from vapor to liquid at five different refrigerant mass fluxes between 150 kg/m2s and 750 kg/m2s. Results from previous work by the authors were used to select the data that correspond to the intermittent flow regime; generally, these points had qualities less than 25%. The pressure drop model previously developed by the authors for circular microchannels was used as the basis for the model presented in this paper. The model includes the contributions of the liquid slug, the vapor bubble, and the transitions between the bubbles and slugs. Slug frequency was estimated using a simple correlation for non-dimensional unit-cell length. The model predicts the experimentally measured pressure drops for the noncircular tube shapes under consideration with 90% of the predictions within ±28% of the measurements (average error 16.5%), which is shown to be much better than the predictions of other models in the literature. The effects of tube shape on condensation pressure drop are also illustrated in the paper.

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An Expermentally Validated Model for Two-Phase Pressure Drop in the Intermittent Flow Regime for Noncircular Microchannels

Journal of Fluids Engineering ◽

10.1115/1.1601258 ◽

2003 ◽

Vol 125 (5) ◽

pp. 887-894 ◽

Cited By ~ 58

Author(s):

Srinivas Garimella ◽

Jesse D. Killion ◽

John W. Coleman

Keyword(s):

Pressure Drop ◽

Flow Regime ◽

Intermittent Flow ◽

Average Error ◽

Two Phase ◽

Pressure Drops ◽

Mass Fluxes ◽

Tube Shape ◽

Measured Pressure ◽

Phase Pressure

This paper reports the development of an experimentally validated model for pressure drop during intermittent flow of condensing refrigerant R134a in horizontal, noncircular microchannels. Two-phase pressure drops were measured in six noncircular channels ranging in hydraulic diameter from 0.42 mm to 0.84 mm. The tube shapes included square, rectangular, triangular, barrel-shaped, and others. For each tube under consideration, pressure drop measurements were taken over the entire range of qualities from vapor to liquid at five different refrigerant mass fluxes between 150 kg/m2s and 750 kg/m2s. Results from previous work by the authors were used to select the data that correspond to the intermittent flow regime; generally, these points had qualities less than 25%. The pressure drop model previously developed by the authors for circular microchannels was used as the basis for the model presented in this paper. Using the observed slug/bubble flow pattern for these conditions, the model includes the contributions of the liquid slug, the vapor bubble, and the transitions between the bubble and slugs. A simple correlation for nondimensional unit-cell length was used to estimate the slug frequency. The model successfully predicts the experimentally measured pressure drops for the noncircular tube shapes under consideration with 90% of the predictions within ±28% of the measurements (average error 16.5%), which is shown to be much better than the predictions of other models in the literature. The effects of tube shape on condensation pressure drop are also illustrated in the paper.

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