An experimental and numerical investigation of the combustion and heat transfer characteristics of hydrogen-fueled catalytic microreactors

Sui, Ran; Prasianakis, Nikolaos I.; Mantzaras, John; Mallya, Nithin; Theile, J.; Lagrange, Damien; Frieß, Martin

doi:10.1016/j.ces.2015.10.034

Cited by 49 publications

(20 citation statements)

References 53 publications

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“…Alternatively, syngas can be converted to power in a more portable/smaller scale. This can be achieved by catalytically stabilized thermal combustion, which is currently being investigated by e.g., the Combustion Research Group at the Paul Scherrer Institute (Villigen, Switzerland) [251][252][253][254][255][256][257][258][259]. In these studies, the researchers focus on converting fuel/syngas mixtures, via a combination of heterogeneous-homogeneous reactions, over platinum-based catalysts coated onto micro-channels.…”

Section: Catalytic Combustionmentioning

confidence: 99%

Monoliths: A Review of the Basics, Preparation Methods and Their Relevance to Oxidation

2017

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Considerable research has been conducted on monolithic catalysts for various applications. Strategies toward coating monoliths are of equal interest and importance. In this paper, the preparation of monoliths and monolithic catalysts have been summarized. More specifically, a brief explanation for the manufacturing of ceramic and metallic monoliths has been provided. Also, different methods for coating γ-alumina, as a secondary support, are included. Techniques used to deposit metal-based species, zeolites and carbon onto monoliths are discussed. Furthermore, monoliths extruded with metal oxides, zeolites and carbon are described. The main foci are on the reasoning and understanding behind the preparation of monolithic catalysts. Ideas and concerns are also contributed to encourage better approaches when designing these catalysts. More importantly, the relevance of monolithic structures to reactions, such as the selective oxidation of alkanes, catalytic combustion for power generation and the preferential oxidation of carbon monoxide, has been described.

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Section: Catalytic Combustionmentioning

confidence: 99%

Monoliths: A Review of the Basics, Preparation Methods and Their Relevance to Oxidation

2017

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“…For the heterogeneous chemistry of hydrogen, the detailed heterogeneous reaction scheme of Deutschmann et al (2000) is employed, consisting of 11 irreversible and 3 reversible elementary reactions with 6 gaseous and 5 surface species. The above homogeneous and heterogeneous reaction mechanisms have reproduced the measured catalytic conversions and the homogeneous ignition distances in fuel-lean and fuel-rich hydrogen-air mixtures over platinum (Schultze et al, 2013;Sui et al, 2016).…”

Section: Chemical Kineticsmentioning

confidence: 63%

Computational Fluid Dynamics Simulation of the Thermal Uniformity in Catalytic Micro-Combustors

Chen¹,

Song²,

Xu³

2017

Frontiers in Heat and Mass Transfer

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The combustion and heat transfer characteristics of hydrogen-air or methane-air mixtures in catalytic micro-combustors were studied numerically to assess the impact of wall thermal properties and key operation parameters on the thermal uniformity. A two-dimensional computational fluid dynamics (CFD) model was developed with detailed hetero-/homogeneous chemistry, heat conduction within the solid wall, surface radiation heat transfer, and external heat losses. Parametric studies were carried out to investigate the effect of wall thermal conductivity, feed composition, and flow rate on the thermal uniformity during highly exothermic catalytic reactions. Comparisons of hydrogen-with methane-air systems were made. Based on these insights, an overall energy balance analysis was performed in terms of enthalpy loss. It was shown that the wall thermal properties strongly affect the thermal uniformity, but little impact on the extinction limit and conversion. The feed composition and flow rate have a significant impact on the operating temperature, but only a moderate effect on the thermal uniformity. Most of the enthalpy released by the exothermic reaction is lost to the surroundings under certain conditions, although this energy exchange becomes less efficient as the flow rate increases. This feature is beneficial for heat-exchanger applications.

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“…As such, microreactors are of interest for chemical synthesis [1,8,9] and are particularly suited to highly exothermic and endothermic reactions [5,10,11]. Experimental investigations of transport in microreactors have been conducted and comparisons have been made with the numerical analyses [12][13][14]. In particular, the enclosing structure (thick walls of the microreactor) was found to have significant impacts upon the performance of microreactors [15][16][17].…”

Section: Introductionmentioning

confidence: 99%

The effects of exothermic catalytic reactions upon combined transport of heat and mass in porous microreactors

Hunt

Karimi

Yadollahi

et al. 2019

International Journal of Heat and Mass Transfer

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Microreactors for chemical synthesis and combustion have already attracted significant attention. Exothermic catalytic activity features heavily in these devices and thus advective-diffusive transport is of key importance in their analyses. Yet, thermal modelling of the heat generated by catalytic reactions on the internal surfaces of porous microreactors has remained as an important unresolved issue. To address this, the diffusion of heat of catalytic reactions into three phases including fluid, porous solid and solid walls is investigated by extending an existing interface model of porous media under local thermal non-equilibrium. This is applied to a microchannel fully filled with a porous material, subject to a heat flux generated by a catalytic layer coated on the porous-wall boundary. The finite wall thickness and viscous dissipation of the flow kinetic energy are considered, and a twodimensional analytical model is developed, examining the combined heat and mass transfer and thermodynamic irreversibilities of the system. The analytical solution is validated against the existing theoretical studies on simpler configurations as well as a computational model of the microreactor in the limit of very large porosity. In keeping with the recent findings, the wall thickness is shown to strongly influence the heat and mass transport within the system. This remains unchanged when the symmetricity of the microchannel is broken through placing walls of unequal thicknesses, while deviation from local thermal equilibrium is significantly intensified in this case. Importantly, the Nusselt number is shown to have a singular point, which remains fixed under various conditions. NomenclatureInterfacial area per unit volume of porous media, (m -1 ) Prandtl number Biot number Wall heat flux ratio ′ Modified Brinkman number ′′ Total catalytic heat flux (W m -2 ) Mass species concentration (kg m -3 ) 1 ′′ Lower wall heat flux (W m -2 ) 0 Inlet concentration (kg m -3 ) 2 ′′ Upper wall heat flux (W m -2 ) Specific heat capacity (J K -1 kg -1 ) Reynolds number Mass diffusion coefficient (m 2 s -1 ) Specific gas constant (J K -1 kg -1 ) Darcy number Shape factor of the porous medium Coefficient of thermal mass diffusion (m K -1 kg -1 s -1 ) ̇′ ′′ Volumetric entropy generation due to mass diffusion (W K -1 m -3 ) ℎ 1 Half-thickness of the microchannel to lower wall (m) ′ ′′ Volumetric entropy generation due to fluid friction (W K -1 m -3 ) ℎ 2 Half-thickness of the microchannel to upper wall (m) ̇′ ′′ Volumetric entropy generation in the fluid (W K -1 m -3 ) ℎ 3 Half-height of microchannel (m) ′ ′′ Volumetric entropy generation in the porous solid (W K -1 m -3 ) ℎ Interstitial heat transfer coefficient (W K -1 m -2 ) ̇1 ′′′ Volumetric entropy generation rate from lower wall (W K -1 m -3 )

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An experimental and numerical investigation of the combustion and heat transfer characteristics of hydrogen-fueled catalytic microreactors

Cited by 49 publications

References 53 publications

Monoliths: A Review of the Basics, Preparation Methods and Their Relevance to Oxidation

Monoliths: A Review of the Basics, Preparation Methods and Their Relevance to Oxidation

Computational Fluid Dynamics Simulation of the Thermal Uniformity in Catalytic Micro-Combustors

The effects of exothermic catalytic reactions upon combined transport of heat and mass in porous microreactors

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