Modeling the Effect of Channel Tapering on the Pressure Drop and Flow Distribution Characteristics of Interdigitated Flow Fields in Redox Flow Batteries

Optimization of flow fields in redox flow batteries can increase performance and efficiency, while reducing cost. Therefore, there is a need to establish a fundamental understanding on the connection between flow fields, electrolyte flow management and electrode properties. In this work, the flow distribution and pressure drop characteristics of interdigitated flow fields with constant and tapered cross-sections are examined numerically and experimentally. Two simplified 2D along-the-channel models are used: (1) a CFD model, which includes the channels and the porous electrode, with Darcy’s viscous resistance as a momentum sink term in the latter; and (2) a semi-analytical model, which uses Darcy’s law to describe the 2D flow in the electrode and lubrication theory to describe the 1D Poiseuille flow in the channels, with the 2D and 1D sub-models coupled at the channel/electrode interfaces. The predictions of the models are compared between them and with experimental data. The results show that the most influential parameter is γ , defined as the ratio between the pressure drop along the channel due to viscous stresses and the pressure drop across the electrode due to Darcy’s viscous resistance. The effect of R e in the channel depends on the order of magnitude of γ , being negligible in conventional cells with slender channels that use electrodes with permeabilities in the order of 10 − 12 m 2 and that are operated with moderate flow rates. Under these conditions, tapered channels can enhance mass transport and facilitate the removal of bubbles (from secondary reactions) because of the higher velocities achieved in the channel, while being pumping losses similar to those of constant cross-section flow fields. This agrees with experimental data measured in a single cell operated with aqueous vanadium-based electrolytes.

Download Full-text

Modeling flow distribution and pressure drop in redox flow batteries

AIChE Journal ◽

10.1002/aic.16330 ◽

2018 ◽

Vol 64 (10) ◽

pp. 3746-3755 ◽

Cited By ~ 8

Author(s):

Malcolm MacDonald ◽

Robert M. Darling

Keyword(s):

Pressure Drop ◽

Flow Distribution ◽

Redox Flow Batteries ◽

Flow Batteries ◽

Modeling Flow

Download Full-text

Rechargeable redox flow batteries: flow fields, stacks and design considerations

Chemical Society Reviews ◽

10.1039/c8cs00072g ◽

2018 ◽

Vol 47 (23) ◽

pp. 8721-8743 ◽

Cited By ~ 67

Author(s):

Xinyou Ke ◽

Joseph M. Prahl ◽

J. Iwan D. Alexander ◽

Jesse S. Wainright ◽

Thomas A. Zawodzinski ◽

...

Keyword(s):

Flow Fields ◽

Review Article ◽

Next Generation ◽

Redox Flow Batteries ◽

Design Considerations ◽

Flow Batteries

This review article summarizes the development of flow fields and stacks, and design considerations for next-generation flow batteries.

Download Full-text

A gradient porous electrode with balanced transport properties and active surface areas for vanadium redox flow batteries

Journal of Power Sources ◽

10.1016/j.jpowsour.2019.227159 ◽

2019 ◽

Vol 440 ◽

pp. 227159 ◽

Cited By ~ 11

Author(s):

H.R. Jiang ◽

B.W. Zhang ◽

J. Sun ◽

X.Z. Fan ◽

W. Shyy ◽

...

Keyword(s):

Transport Properties ◽

Porous Electrode ◽

Active Surface ◽

Redox Flow Batteries ◽

Surface Areas ◽

Flow Batteries ◽

Vanadium Redox

Download Full-text

NUMERICAL STUDY OF THE EFFECT OF AREA OF MANIFOLD AND INLET/OUTLET FLOW ARRANGEMENT 0N FLOW DISTRIBUTION IN PARALLEL RECTANGULAR MICROCHANNEL COOLING SYSTEM

Jurnal Teknologi ◽

10.11113/jt.v79.11901 ◽

2017 ◽

Vol 79 (7-3) ◽

Author(s):

Amirah M. Sahar ◽

A. I. M. Shaiful

Keyword(s):

Experimental Data ◽

Pressure Drop ◽

Cooling System ◽

Numerical Study ◽

Flow Distribution ◽

Fluid Temperature ◽

Rectangular Microchannel ◽

Temperature Distributions ◽

Micro Channels ◽

Parallel Microchannels

Parallel microchannels have been widely used in cooling of compact electronic equipment due to large contact area with liquid and availability of large mass of fluid to carry away heat. However, understanding of flow distribution for microchannel parallel system is still unclear and there still lack of studies give a clear pictures to understand the complex flow features which cause the flow maldistribution. Generally, the geometrical structure of the manifold and micro channels play an important role in flow distribution between micro channels, which might affects the heat and mass transfer efficiency, even the performance of micro exchangers. A practical design of exchanger basically involves the selection of an optimized solution, keeping an optimal balance between gain in heat transfer and pressure drop penalty. A parallel microchannels configurations consisting inlet and outlet rectangular manifold were simulated to study flow distribution among the channels were investigated numerically by using Ansys Fluent 14.5. The numerical results was validated using existing experimental data and showed a similar trend with values 1% higher than experimental data. The influence of inlet/outlet manifold area and inlet/outlet arrangement on flow distribution in channels were carried out in this study. Based on the predicted flow non-uniformity value, 𝜙, Z- type flow arrangement exhibits higher value of 𝜙, which is 8%, followed by U-type, 2.6% and the I-type, 2.49%. Thus, a better uniformity of velocity and temperature distributions can be achieved in I-shape flow arrangement. The behavior of the flow distributions inside channels is due to the vortices that occurred at manifold. Besides comparing the pressure drop for case 1(D1) and case 2(D2), it is worth to mention that, as the area of inlet and outlet manifold decrease by 50%, the pressure drop is increasing about 5%. However, the inlet/outlet area of manifold on velocity and fluid temperature distributions was insignificant.

Download Full-text

Modeling of the Anode Flow Fields in DMFCs

International Journal of Chemical Reactor Engineering ◽

10.2202/1542-6580.1728 ◽

2008 ◽

Vol 6 (1) ◽

Cited By ~ 1

Author(s):

Ugo A. Icardi ◽

Stefania Specchia ◽

Guido Saracco ◽

Vito Specchia

Keyword(s):

Pressure Drop ◽

Average Velocity ◽

Direct Methanol Fuel Cells ◽

Membrane Surface ◽

Flow Distribution ◽

Flow Fields ◽

Field Pattern ◽

Direct Methanol ◽

Interdigitated Flow Field ◽

Pass Through

Direct Methanol Fuel Cells (DMFCs) have recently attracted the interest of portable applications due to their superior specific energy density compared to the best rechargeable battery and for their potentialities of instantaneous refueling. The most recent literature in the field of DMFCs has directed increasing interest on the role of the flow fields on the performance of the FC itself. The most "primitive" designs (e.g. parallel channels) have generally been dismissed and substituted by serpentine or interdigitated flow patterns. The serpentine pattern forces the entire feed flow rate to pass through a serpentine spanning over the entire electrode surface. This system is particularly suited to drive gas bubbles out of the system and therefore it seems to be particularly suited for the methanol side. The interdigitated flow field pattern is particularly suitable only for the air feed to the DMFC. The effect of the channel and graphite rib geometries is of critical importance. The choice of the correct geometry is thus a question of compromise which can be drawn on the grounds of modeling calculations and experimental checks. A series of simulations in CFD (fluent 6.1) were thus performed on a multichannel serpentine matrix for the anode side (methanol feed) piled up in a stack hosting 40 MEAs (nominal power 250 W; 222 cm2 membrane surface per cell). Three different channel geometries were modeled. This paper shows that a series flow is not suitable for the too high pressure drop and average velocity into channels it implies. Optimal flow distribution (i.e. low pressure drop, acceptable average velocity and a good methanol distribution) seems to be guaranteed with three serpentines per cell for fuel cell stacks of a nominal power of 250 W.

Download Full-text