• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.1105-1117
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• 2023

In this study, the pressure drop behavior of single- and two-phase flows of air and water through the porous beds filled with uniform and non-uniform sized spherical particles was examined. The pressure drop data in the single-phase flow experiments for the uniform particle beds agreed well with the original Ergun correlation. The results from the two-phase flow experiments were analyzed using numerical results based on three types of previous models. In the experiments for the uniform particle beds, the data on the two-phase pressure drop clearly showed the effect of the flow regime transition with a variation in the gas flow rate under stagnant liquid condition. The numerical analyses indicated that the predictability of the previous models for the experimental data relied mainly on the sub-models of the flow regime transitions and interfacial drag. In the experiments for the non-uniform particle beds, the two-phase pressure loss could be predicted well with numerical calculations based on the effective particle diameter. However, the previous models failed to accurately predict the counter-current flooding limit observed in the experiments. Finally, we propose a relation of falling liquid velocity into the particle bed by gravity to appropriately simulate the CCFL phenomenon.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.4
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• pp.487-493
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• 2003

More reliable design of thermal transport. Power acquisition and thermal management systems requires the through understanding of the flow hydrodynamic. the differences and similarities between the two-phase flow characteristics of two-Phase flow influenced by the gravity levels. The data of flow Patterns, void fraction, frictional pressure drop associated with their characteristics were obtained at $\mu\textrm{g}$. 1g and 2g. Flow patterns and void fraction data obtained at three gravity levels were compared with each other and previous models and correlations.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.5
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• pp.619-629
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• 1998

An experimental work was conducted to investigate a feasibility of simultaneous measurement of gas-liquid two-phase flowrates with double orifice plates using air and water. The tests were carried out under the atmospheric pressure and at the ambient temperature using two different tube sizes. Qualities of an air-water flow in the present study have values less than 0.1 and thus the mixed flow showed bubbly, plug, slug flow regimes. The probability density function (PDF) and the power spectral density function (PSDF) of the instantaneous pressure drop traces for the flow regimes were obtained. It is found that some distinctive features exist in the distribution of these functions, depending upon the two-phase flow pattern. The time-averaged value of the instantaneous pressure drop increases with increasing gas and liquid flowrates, showing a single-valued function for the total mass flowrate and the quality. It is also found that the two-phase discharge coefficient exhibits a consistent trend for variation of dimensionless parameters such as the superficial velocity ratio and the gas Reynolds number. The results indicate that simultaneous measurement of two-phase flowrate may be possible based upon a statistical analysis of the instantaneous pressure drop curves monitored using double orifice plates.

• Journal of Mechanical Science and Technology
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• v.17 no.5
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• pp.758-765
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• 2003

An experimental investigation on the flow pattern and pressure drop was carried out for both an adiabatic and a diabatic two-phase flow in a horizontal tube with pure refrigerants R134a and R123 and their mixtures as test fluids. The observed flow patterns were compared to the flow pattern map of Kattan et al., which predicted well the present data over the entire regions of mass velocity in this study. The measured frictional pressure drop in the adiabatic experiments increased with an increase in vapor quality and mass velocity These data were compared to various correlations proposed in the past for the frictional pressure drop. The Chisholm correlation underpredicted the present data both for pure fluids and their mixtures in the entire mass velocity range of 150 to 600 kg/m$^2$s covered in the measurements, white the Friedel correlation was found to overpredict the present data in the stratified and stratified-wavy flow region, and to underpredict in the annular flow region.

• 한국전산유체공학회:학술대회논문집
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• 2004.03a
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• pp.190-195
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• 2004

The pressure drop in a Venturi Scrubber is predicted using the Eulerian-Lagrangian Method, which is one of the numerical methods to solve the dispersed two-phase flow. KIVA-3V Code is modified to solve the coupled gas-liquid two-phase flow field. The liquid is assumed to be injected through the nozzles with the Rosin-Rammler drop size distribution. The computational results shows good agreement with the experimental data.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.1882-1887
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• 2007

In the present experimental study, the effect of interfacial tensions on pressure drop of air-water two-phase flow in round mini-channels was investigated. A glass (highly wettable) tube and a Teflon (poorly wettable) tube, both in 350 mm length but 1.8 mm and 1.59 mm in inner diameters each, were used for the tests. All the experiments were performed only in the plug flow regime, confirmed by visualization. In the glass tube, the gas plugs were surrounded by the liquid film along the inner periphery. On the other hand, the inner wall remained dry at the gas portion in the Teflon tube. The pressure drop of the plug flow in the Teflon tube without the liquid film) appeared much larger than in the glass tube (with the liquid film) due to dissipation of energy by movement of the wetting lines. In this paper, various correlations on the two-phase pressure drop of plug flows were compared and a modified correlation was proposed, taking account of the surface wettability.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.5
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• pp.637-645
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• 1999

Horizontal two-phase flow pressure drop within rectangular channels with small gap heights have been examined experimentally. The gap heights range from 0.4mm to 4mm corresponding to aspect ratios(the channel height divided by the width) from 0.02 to 0.2. Water and air were used as the test fluids with the superficial velocity ranges being 0.03-2.39m/s and 0.05-18.7m/s, respectively. The experimental results In rectangular channels were compared with the Lockhart-Martinelli correlation, which are widely used for conventional round tube. The Lockhart-Martinelli correlation turned out to be Inappropriate to represent the present experimental data. In this respect, considering the aspect ratio and gap-height effects, an empirical correlation on two-phase flow pressure drop was proposed. The proposed correlation successfully covers the bubbly, plug, slug and annular flow regimes.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.7
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• pp.881-892
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• 1999

Experiment was performed to study the characteristics of pressure drop of multi-channel tubes for automotive condenser using HFC-134a. Single phase liquid and two phase flow pressure drop were measured in one rectangular plain and three micro-fin tubes with 10 channels. Data are presented for the following range of variables: mass flux(200 to $600kg/m^2s$), and inlet saturation pressure of the refrigerant(1.0 and 1.6MPa). For subcooled flow, pressure drops are 10% and 12% higher than that predicted by the Petukhov equation with hydraulic diameter respectively. Two-phase flow pressure drop are compared with the previously proposed correlations, and well predicted by modified correlation that was derived from Traviss correlation. and correlated within -30~+20%. Also experimental data are correlated within -56%~+18% by Webb's prediction method based on the equivalent mass velocity concept originally proposed by Akers et al.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.11a
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• pp.301-306
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• 1996

To predict the average liquid level under the condition of the countercurrent stratified two-phase flow in a pipe, an analytical model has been suggested. This is made by introducing the interfacial level gradient into the liquid-phase and the gas-phase momentum equations. The analytical method for the gas-phase pressure drop calculation with f$_i$ $\neq$ f$_G$ has also been described using the liquid level prediction model developed in the present study.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.21-27
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• 2003

This paper proposes a new model of the pressure drop for more accurate description of oscillating flow through regenerator under pulsating pressure conditions in contrast to an existing model based on steady flow. For the universal uses of the oscillating flow model, non-dimensional parameters, which consist of Reynolds number, Valensi number gas domain length ratio, oscillating flow friction factor and phase angle of pressure drop, are derived from the capillary tube model of the regenerator. Two correlation equations of the model are obtained from the experiments for the twill square screen regenerators under various operating frequencies and inlet mass flow rates. The oscillating friction factor is a function of only the Reynolds number and the phase angle of pressure drop is a function of the Valensi number and the gas domain length ratio. Experiment is also performed to examine the effects of the shape of screens.