ON THE LOW REYNOLDS NUMBER MASS TRANSFER IN PACKED BEDS

Low-Reynolds-number laminar channel flow is used in various heat/mass transfer applications, such as cooling and mixing. A low Reynolds number implies a low intensity of heat/mass transfer processes, since they rely only on the gradient diffusion. To enhance these processes, an active flow control by means of synthetic (zero-net-mass-flux) jets is proposed. This arrangement can be promising foremost in microscale. The present study is experimental in which a Reynolds number range of 200–500 is investigated. Measurement was performed mainly in air as the working fluid by means of hot-wire anemometry and the naphthalene sublimation technique. PIV experiments in water are also discussed. The experiments were performed in macroscale at the channel cross-section (20×100)mm and (40×200)mm in air and water, respectively. The results show that the low Reynolds number channel flow can be actuated by an array of synthetic jets, operating near the resonance frequency. The control effect of actuation and the heat transfer enhancement was quantified. The stagnation Nusselt number was enhanced by 10–30 times in comparison with the non-actuated channel flow. The results indicate that the present arrangement can be a useful tool for heat transfer enhancement in various applications, e.g., cooling and mixing.

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Numerical Predictions of Uniform CO2 Corrosion in Complex Fluid Domains Using Low Reynolds Number Models

Metals ◽

10.3390/met8121001 ◽

2018 ◽

Vol 8 (12) ◽

pp. 1001

Author(s):

Haijun Hu ◽

Hao Xu ◽

Changmeng Huang ◽

Xing Chen ◽

Xiufeng Li ◽

...

Keyword(s):

Experimental Data ◽

Mass Transfer ◽

Reynolds Number ◽

Low Reynolds Number ◽

Co2 Corrosion ◽

Aqueous Corrosion ◽

Corrosion Rates ◽

Complex Fluid ◽

Low Reynolds ◽

Near Wall

To get the knowledge of local corrosion, thinning is useful for developing targeted inspection plans for pipe components in the oil/gas industry. Aiming at this object, this work presents a computer fluid dynamics (CFD) method to predict CO2 aqueous corrosion in complex fluid domains. The processes involved in CO2 aqueous corrosion, including flow dynamics, mass transfer, chemical reactions, and electrochemical reactions, are modeled and simulated by a commercial CFD software of Fluent V15.0 (Version, manufacturer, city, country). Mass transfer in the straight pipe flow and jet impinging flow are simulated using three low-Reynolds-number turbulent models (Abe–Kondoh–Nagano k − ε model, Change–Hsieh–Chenk k − ε model, and k − ε shear stress transport model). The flow domains are meshed by grids with the first near-wall node at the position at y+ = 0.1. Comparisons between simulations and experimental data show the Abe–Kondoh–Nagano model provides the best predictions of near-wall flow and mass transfer. Thus, it is used to predict CO2 aqueous corrosion. Corrosion rates of dissolved CO2 in straight pipes and a jet impinging are predicted. The predicted corrosion rates are compared with experimental data and results derived from commercial software, Multicorp V5.2.105. The results show that predicted corrosion rates are reasonable. The locations of the highest corrosion rate for a jet impinging system are revealed.

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Heat/Mass Transfer Characteristics for Flow in a Corrugated Wall Channel

Journal of Heat Transfer ◽

10.1115/1.3450667 ◽

1977 ◽

Vol 99 (2) ◽

pp. 187-195 ◽

Cited By ~ 152

Author(s):

Leonardo Goldstein ◽

E. M. Sparrow

Keyword(s):

Mass Transfer ◽

Reynolds Number ◽

Secondary Flow ◽

Low Reynolds Number ◽

Secondary Flows ◽

Turbulent Regime ◽

Transfer Rates ◽

Transfer Characteristics ◽

Low Reynolds ◽

Corrugated Wall

Experiments based on the naphthalene sublimation technique were carried out to determine the local and average transfer characteristics for flow in a corrugated wall channel. The range of the experiments encompassed the laminar, transition, and low-Reynolds-number turbulent regimes. Local mass transfer measurements were made both in the spanwise (i.e., cross stream) and streamwise directions, and overall transfer rates were also determined. The experiments demonstrated the existence of a variety of complex transfer processes and related fluid flow phenomena. These included secondary flows and associated spanwise mass transfer variations, suppression of the secondary flow by counteracting centrifugal forces, and destruction of the secondary flow by the onset of turbulence. Flow separation on the leeward facets of the corrugated wall caused a sharp decrease in the local transfer rates, but relatively high transfer rates were in evidence in the reattachment region. In the laminar range, the average transfer coefficients for the corrugated wall channel were only moderately larger than those for a parallel-plate channel. On the other hand, in the low-Reynolds-number turbulent regime, the wall corrugations were responsible for an increase of nearly a factor of three in the average coefficient compared with the smooth wall channel.

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