Numerical Study of the Dynamic Response of Heat and Mass Transfer to Operation Mode Switching of a Unitized Regenerative Fuel Cell

Hong, Xia; Guo, Hang; Ye, Fang; Ma, Chongfang

doi:10.3390/en9121015

Cited by 29 publications

(19 citation statements)

References 41 publications

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“…The results showed that maximum relative error between the numerical and experimental data is in an acceptable range. Besides, the presented three‐dimensional model is in better agreement with the experimental data than that in the study of Xiao et al with two‐dimensional mode. This is because the effects of the mass and heat transfer originating from the third dimension ( x axial) on electric performance were considered in this model.…”

Section: Element Independence and Model Validationsupporting

confidence: 76%

“… The effect of mass transfer along width direction of porous payers on cell behavior is presented based on the presented three‐dimensional model. The slight reductions on current density and hydrogen generation occur during mode switching; however, it is not presented in our previous published two‐dimensional model because of the neglect of the third dimension. Local water starvation occurs during mode switching. This is because supplied water cannot fully transport into oxygen side CL within 0.33 second for participating in electrochemical reaction in electrolytic mode.…”

Section: Discussionmentioning

confidence: 84%

“…The general form of the thermal conservation equation can be described as follows:

\partial ((), ρ c_{p} T) / \partial t + \nabla \cdot ((), ρ c_{p} bold-italicu T) = \nabla \cdot ((), k_{eff} \nabla T) + S_{T},

where ρ and c p are the local density and specific heat capacity at a constant pressure of each subdomain, respectively, and k eff is the effective or equivalent thermal conductivity. Generally, heat generation in cells consists of reversible heat caused by electrochemical reactions, irreversible heat caused by the electrochemical reactions, and Joule heating . Irreversible heat attributed to activation polarizations exists on OCLs.…”

Section: Model Descriptionmentioning

confidence: 99%

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Heat and mass transfer in a unitized regenerative fuel cell during mode switching

Guo

et al. 2018

Int J Energy Res

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Summary With the occurrence of reversible electrochemical reactions, mode switching considerably affects the electric performance of unitized regenerative fuel cells (URFCs) owing to the complicated mass and heat transfer. Although limited researches have been done, no such studies on mass and heat transfer through a three‐dimensional view are envisioned during mode switching. A three‐dimensional full‐cell model was developed and validated to study the dynamic characteristics of a proton exchange membrane‐based URFC during mode switching. Mode switching was performed by changing operation voltage from 0.60 to 1.65 V. Results showed that species and heat transfer affect the electric performance of the cell during mode switching, especially through the third dimensional. Local water starvation occurs on oxygen side catalyst layer and thus results in slight reduction on current density and hydrogen generation. Restricted to heat transfer capacity through ribs, heat transfer process adds total response time in URFCs. Heat flux and surface heat transfer coefficient are forecasted on the hydrogen and oxygen sides. A total time of 4 seconds is essential for URFC reaching a new relative balanced state.

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Section: Element Independence and Model Validationsupporting

confidence: 76%

Section: Discussionmentioning

confidence: 84%

“…The general form of the thermal conservation equation can be described as follows:

\partial ((), ρ c_{p} T) / \partial t + \nabla \cdot ((), ρ c_{p} bold-italicu T) = \nabla \cdot ((), k_{eff} \nabla T) + S_{T},

Section: Model Descriptionmentioning

confidence: 99%

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Heat and mass transfer in a unitized regenerative fuel cell during mode switching

Guo

et al. 2018

Int J Energy Res

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“… The mixture of gas components is considered an incompressible ideal gas. The thermal contact resistance between each layer is neglected. The effect of gravity is negligible. Vapor‐liquid phase change only occurs in oxygen side. The porous medium is uniform and isotropic. The flow channel is considered the porous medium, with a porosity of 1. Thus, the liquid saturation in the oxygen‐side channel is continuous. The membrane is impermeable to gas.…”

Section: Model Descriptionmentioning

confidence: 99%

Mass transfer and cell performance of a unitized regenerative fuel cell with nonuniform depth channel in oxygen‐side flow field

Jia

Guo

et al. 2019

Int J Energy Res

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Summary In this study, the cell performance of nonuniform depth and conventional straight channel in a unitized regenerative fuel cell (URFC) is compared. Various shapes of oxygen‐side channel cases are also proposed. Several parameters, such as the distribution of reactants and products and current density and powers in fuel cell (FC) and electrolytic cell (EC) modes, are investigated. A steady‐state model of two‐dimensional, two‐phase, nonisothermal, and coupled electrochemical reaction is developed. Five oxygen‐side channel shapes are also designed, in which the depth along the flow direction is narrowed. Result shows that narrowing the average channel depth can promote and guide the reactant transfer to the catalyst layer and avoid the blocking of the production. Thus, in comparison with the conventional channel, the cell performances of nonuniform depth and shallow straight channel cases are improved in both modes. In addition, with the decrease of average channel depth, the temperature uniformity gets better, which is also conductive to the improvement of cell performance. Furthermore, in FC mode at low voltage and EC mode, the cell net power basically increases with the decrease of the average channel depth ratio. And when the average channel depth is the same, the net power of straight channel is always lower than nonuniform depth case. This study introduces the round‐trip energy efficiency as an evaluation indicator of URFC. This efficiency can be increased by improving the cell performance of both modes, especially at high current density.

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“…The species distributions were obtained. Heat transfer was investigated in a subsequent work . Xiao et al investigated various mode switching by a 2‐dimensional model.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation on two-phase flow in a unitized regenerative fuel cell during mode switching from water electrolyzer to fuel cell

et al. 2018

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Summary Mode switching between fuel cell and water electrolyzer of a unitized regenerative fuel cell alters two‐phase flow dynamics in the channels. To fully understand the mode switching, the observation of two‐phase flow is necessary. In this work, experiments are conducted to investigate the two‐phase flow in the flow field of a unitized regenerative fuel cell during mode switching. A transparent window is assembled at the oxygen side to allow a direct view of the serpentine flow field. The two‐phase flow are captured by a high‐speed camera. Water has a significant effect on the mode switching. The switching from water electrolyzer to fuel cell is difficult because of the flooding problem. High temperature causes insufficient water in water electrolyzer mode without water supply and membrane dehydration in fuel cell mode. The voltage in fuel cell mode decreases more rapidly with fuel cell current density during mode switching.

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Numerical Study of the Dynamic Response of Heat and Mass Transfer to Operation Mode Switching of a Unitized Regenerative Fuel Cell

Cited by 29 publications

References 41 publications

Heat and mass transfer in a unitized regenerative fuel cell during mode switching

Heat and mass transfer in a unitized regenerative fuel cell during mode switching

Mass transfer and cell performance of a unitized regenerative fuel cell with nonuniform depth channel in oxygen‐side flow field

Experimental investigation on two-phase flow in a unitized regenerative fuel cell during mode switching from water electrolyzer to fuel cell

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