Flow regime transitions during condensation in microchannels

Nema, Gaurav; Garimella, Srinivas; Fronk, Brian M.

doi:10.1016/j.ijrefrig.2013.11.018

Cited by 117 publications

(14 citation statements)

References 58 publications

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“…Figure 7 (c) shows the liquid/sand mixture in the turbulent region caused by the wake entrainment of the elongate gas bubble. This is consistent with experimental observations demonstrating that slug flow can be expected after an annular flow pass through a bend (Nema, 2008;Abdulkadir, 2011). In addition, according to the particle directions shown in Figure 7, the area of maximum erosion is expected to be located in the bend.…”

Section: Effect Of Flow Development On Erosionsupporting

confidence: 90%

Advances in Multiphase Flow CFD Erosion Analysis

et al. 2013

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One of the flow assurance challenges in subsea production systems is the occurrence of erosion damage due to the existence of sand particles and high production Gas Oil Ratio (GOR) as such erosion mostly occurs in highly gas dominated operating conditions in the annular flow regime. The erosion rate for an elbow with a constant flow velocity and with all other factors equal is higher in gas systems than liquid systems as more particles will impact on the inner wall of the outer curvature of the elbow. The maximum wear location and the penetration rate for multiphase flows are often an intermediary of gas and liquid systems occurring at 55 degrees from the inlet of the elbow, however this depends heavily on the multiphase flow regime. A challenge facing industry is availability of erosion prediction models; the majority of available models are based on singlephase liquid or gas as the carrying medium. This can result in large discrepancies in erosion rates and potentially increased wall thickness, fabrication and subsequent intervention costs.To predict the flow regime in greater clarity requires the use of computational power and / or instrumentation that can accurately characterize the flow within the pipes. Since experimental work is costly and unlikely to be representative of a large integrated production system, Computational Fluid Dynamics (CFD) is used to perform erosion assessments and can also aide in corrosion prediction and inhibitor selection. Only erosion assessments by CFD methods are discussed in detail within this paper. CFD has been extensively applied for erosion analyses; it is commonly used for identifying potential failure locations, improving understanding of failure mechanisms and only qualitatively used for erosion rates.CFD erosion modelling capability in this paper has been enhanced by simulating flow regime characteristics, in particular the liquid film for annular flow. This benefits the simulation to obtain greater accuracy for sand particle impact angles, area, speed and thus the erosion rate is significantly enhanced. In addition, the local volume fraction of sand has been considered in order to accurately evaluate the impact force. The research to date shows that a promising agreement is obtained between predicted erosion rate and the empirical predictions (Salama, Salama & Venkatesh and DNV RP-501 methods).Further comparisons to empirical model predictions are carried out to address the importance of flow regime on the results as current empirical models lack this consideration. The influence of the flow orientation (upwards and downwards flow), has also been investigated in this work due to current lack of publically available data. The paper presented hereafter illustrates that considerable difference in flow orientation is revealed and the prediction can be improved by considering the flow characteristics. An example is provided highlighting the use of liquid film and droplet velocity to replace the mixture velocity implemented in empirical models for annular flow. All of the fi...

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Section: Effect Of Flow Development On Erosionsupporting

confidence: 90%

Advances in Multiphase Flow CFD Erosion Analysis

et al. 2013

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“…There are also many flow patterns for condensation, such as the maps by Traviss and Rohsenow [116], Palen et al [88], Breber et al [19], Soliman [102], Tandon et al [108], Cavallini et al [21], El Hajal et al [44], Coleman and Garimella [34][35][36], Liebenberg and Meyer [77], and Nema et al [85].…”

Section: Flow Patternsmentioning

confidence: 99%

“…Nema et al [85] proposed a flow map based on dimensionless criteria to capture the combined effect of mass flux, quality, fluid properties and tube size, using the data by Coleman and Garimella [36].…”

Section: Flow Patternsmentioning

confidence: 99%

Numerical study of heat and mass transfer of binary mixtures condensation in mini-channels

Deng

Fernandino

Dorao

2014

International Communications in Heat and Mass Transfer

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“…Therefore, thermophysical properties of working fluid were assumed as constant. For assessing the relative roles of the surface tension and gravity, the Bond number based criteria discussed by Li and Wang [17] and Nema et al [18] are applied, which indicated a subordinate role of the gravity in the present cases. Thus, the gravity is neglected in the present calculations.…”

Section: Introductionmentioning

confidence: 99%

“…According to this map, the flow regime is expected to be annular flow for the cases considered in the present simulations. Nema et al [18] proposed a new flow regime transition criterion for micro channels, according to which, the wavy flow regime is not present if the Bond number is lower than a critical value. In the presently considered cases, the Bond number was lower than this critical Bond number [18].…”

Section: Introductionmentioning

confidence: 99%

Prediction of heat and fluid flow in microchannel condensation

2019

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The condensing flow inside the microchannel has gained importance as the microchannel heat exchangers are widely used in the industry. In this study, a number of numerical simulations on condensing flow inside the microchannel were conducted to investigate heat transfer characteristic. Circularmicrochannel geometries with the various diameters were considered. The Volume of Fluid model was used to model twophase flow. The phase change at the saturation temperature was modeled by the Lee model.In the considered geometries, different from the conventional channels, surface tension forces can be importantcomparedto other forces. Therefore, surface tension was considered in the simulations. Constant wall heatflux and constant saturation temperature were applied as simulation conditions, similar to actual operating conditions. The predictions were validated by comparisons with the experimental results that exist in the literature. A satisfactory agreement of the present predictions with the experimental data was observed.

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Flow regime transitions during condensation in microchannels

Cited by 117 publications

References 58 publications

Advances in Multiphase Flow CFD Erosion Analysis

Advances in Multiphase Flow CFD Erosion Analysis

Numerical study of heat and mass transfer of binary mixtures condensation in mini-channels

Prediction of heat and fluid flow in microchannel condensation

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