Prediction of thermal conductivity of micro/nano porous dielectric materials: Theoretical model and impact factors

Yu, Haiyue; Zhang, Haochun; Buahom, Piyapong; Liu, Jing; Xia, Xin‐Lin; Park, Chul

doi:10.1016/j.energy.2021.121140

Cited by 32 publications

(11 citation statements)

References 94 publications

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“…The experiments for the CLC system with dual interconnected fluidized reactors have been successfully carried out at lab scale and pilot scale, with both gaseous fuel and solid fuel [6][7][8], coal [7,9], petroleum [10], biomass [11] and liquid fuel [12], which prove the feasibility of the CLC technology. At the same, researchers have used the numerical method to investigate the operating behaviour of the CLC system, which is difficult for experimental measurement [13,14], and it has played a more and more important role for investigating the CLC system [15][16][17]. Two main methods, two-fluid model and discrete element method (DEM), are utilized for simulating the CLC system [18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of a 10 kW Gas-Fueled Chemical Looping Combustion Unit

et al. 2022

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Chemical looping combustion is one novel technology for controlling CO2 emission with a low energy cost. Due to a lack of understanding of the detailed and micro behavior of the CLC process, especially for a three dimensional structure, numerical simulations are carried out in this work. The configuration is built according to the experimental unit and gaseous fuel is used in this work. A two-fluid model considering heterogeneous reactions is established, and the flow behaviour and reaction characteristics are obtained. The temperature in the air reactor increases with height owing to the exothermic reaction of the xidation of the oxygen carrier, while the temperature in the fuel reactor decreases with height due to the endothermic reaction. The oxidation level of the oxygen carrier is obtained by simulation, which is hard for measurement, and the difference between the inlet and outlet is 0.065. The influences of the operating temperature and injection rate of fuel are presented to understand the performance of the system. The highest fuel conversion rate reaches 0.92 under high operating temperature. The numerical results are helpful for acquiring insight on the flow and reactive behaviour of CLC reactors.

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Section: Introductionmentioning

confidence: 99%

Numerical Simulation of a 10 kW Gas-Fueled Chemical Looping Combustion Unit

et al. 2022

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“…The most important principle is the effective removal of heat released by the reaction and temperature control in order to maintain catalyst life. However, the complexity of flow behavior and the strongly exothermic effect render it hard to design and scale-up the reactors [11,12]. During the experiments, a bench-scale oil-cooled reactor was used to control the temperature, and the reaction heat was negligible for very low reaction intensities [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

3D Unsteady Simulation of a Scale-Up Methanation Reactor with Interconnected Cooling Unit

2021

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The production of synthetic natural gas (SNG) via methanation has been demonstrated by experiments in bench scale bubbling fluidized bed reactors. In the current work, we focus on the scale-up of the methanation reactor, and a circulating fluidized bed (CFB) is designed with variable diameter according to the characteristic of methanation. The critical issue is the removal of reaction heat during the strongly exothermic process of the methanation. As a result, an interconnected bubbling fluidized bed (BFB) is utilized and connected with the reactor in order to cool the particles and to maintain system temperature. A 3D model is built, and the influences of operating temperature on H2, CO conversion and CH4 yield are evaluated by numerical simulations. The instantaneous and time-averaged flow behaviors are obtained and analyzed. It turns out that the products with high concentrations of CH4 are received at the CFB reactor outlet. The temperature of the system is kept under control by using a cooling unit, and the steady state of thermal behavior is achieved under the cooling effect of BFB reactor. The circulating rate of particles and the cooling power of the BFB reactor significantly affect the performance of reactor. This investigation provides insight into the design and operation of a scale-up methanation reactor, and the feasibility of the CFB reactor for the methanation process is confirmed.

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“…7,9 Wang et al 4 developed a thermal conductivity model for high-temperature alumina aerogel based on real microstructures consisting cube and spherical colloids via a modified parallel-series equivalent electrical circuit approach. Yu et al 10 proposed a novel radiative thermal conductivity model using a combination of fractal thermal conduction methods and Rosseland diffusion equation based on Sierpinski gasket model, Von Koch snowflakes model, and fractalintersecting sphere model. Chen et al 11 suggested an innovative fractal-intersecting sphere with inhomogeneous to derive a thermal conductivity equation including classical Sierpinsky sponge and intersecting spheres structure to be a new fractal-intersecting sphere model to describe microstructure at nanoscale in aerogel composite insulating material.…”

Section: Introductionmentioning

confidence: 99%

Novolac aerogel thermal diffusion and efficiency enhancement using paraffin wax core/polyurethane shell phase‐change material nanocapsules

Abdeali

Bahramian

2021

Intl J of Energy Research

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Summary Aerogels are one of the most promising nano‐dimension open‐cell foams with considerably varied characteristics such as high porosity, super large specific surface area, low density, and super low thermal conductivity. Aerogel's high porosity and microstructure consisting of micro‐ and nanoparticles as well as pores in nanometer dimension are the origin of distinctive properties. However, the main challenge of aerogels is their low density (0.05−0.50 gcm3), which leads to equal thermal diffusion (normalα×10−7) compared with general thermal insulators. To minimize aerogel thermal diffusion and to enhance thermal insulation, replacing some aerogel colloids with phase‐change material nanocapsules (NPCMs) (while aerogel IUPAC definition and at least porosity of 80% is preserved) is proposed in this work. While NPCMs undergo a physical change during phase transfer, temperature becomes persistent, and as a consequence, specific heat capacity (Cp) getting close to an infinite number and thermal diffusion (normalα=knormalρCp) will tend to very low values. Results have demonstrated that by only applying 4.5 wt.% of paraffin wax core /polyurethane shell (PW/PU) NPCMs instead of some novolac aerogel colloids, aerogel has experienced temperature decrement as well as stability. During NPCMs' melting process, thermal diffusivity has reached 2.5×10−12 and temperature increment delay rate has become 40%.

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Prediction of thermal conductivity of micro/nano porous dielectric materials: Theoretical model and impact factors

Cited by 32 publications

References 94 publications

Numerical Simulation of a 10 kW Gas-Fueled Chemical Looping Combustion Unit

Numerical Simulation of a 10 kW Gas-Fueled Chemical Looping Combustion Unit

3D Unsteady Simulation of a Scale-Up Methanation Reactor with Interconnected Cooling Unit

Novolac aerogel thermal diffusion and efficiency enhancement using paraffin wax core/polyurethane shell phase‐change material nanocapsules

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