Effect of Carbon Particle Feeding as Radiant Absorbent for Enhanced Heat Transfer

2021 ◽  
pp. 1-15
Author(s):  
Hamed Abedini ◽  
Nesrin Ozalp
Keyword(s):  
Heat Transfer ◽  
Particle Size ◽  
Temperature Profile ◽  
Energy Absorption ◽  
Carbon Particle ◽  
Carbon Particles ◽  
Solar Reactor ◽  
Simulation Results ◽  
Particle Feeding ◽  
Solar Receiver

Abstract Carbon particles can be used as catalyst in solar reactors where they serve as radiant absorbent and nucleation sites for the heterogeneous decomposition reaction. Unlike commonly used metal catalysts, carbon catalyst does not have durability problem and high cost. However, in order to achieve sustainable catalytic decomposition of feedstock over carbon catalysts at elevated temperatures, the surface area of the carbon particles must be maintained. A subsequent treatment of deactivated carbon samples with CO2 at about 1000 °C would increase the surface and would recover the original activity as catalyst. In a windowed solar reactor, carbon particles are directly exposed to the high flux irradiation providing efficient radiation heat transfer directly to the reaction site. Therefore, one of the key parameters to achieve higher conversion efficiencies in a solar reactor is the presence and transport of carbon particles. In this paper, a transient one-dimensional model is presented to describe effect of carbon particle feeding on energy transport and temperature profile of a cavity-type solar receiver. The model was developed by dividing the receiver into several control volumes and formulating energy balance equations for gas phase, particles, and cavity walls within each control volume. Monte Carlo ray tracing (MCRT) method was used to determine the solar heat absorbed by particles and cavity walls, as well as the radiative exchange between particles and cavity walls. Model accuracy was verified by experimental work using a solar receiver where carbon particles were injected uniformly. Comparison of simulation results with the experimentally measured temperatures at three different locations on cavity receiver wall showed an average deviation of 3.81%. The model was then used to study the effect of carbon particle size and feeding rate on the heat transfer, temperature profile, and energy absorption of the solar receiver. Based on the simulation results, it was found that injection of carbon particles with a size bigger than 500 µm has no significant influence on heat transfer of the system. However, by reducing the particle size lower than 500 µm, temperature uniformity and energy absorption were enhanced.

Effect of Carbon Particle Seeding As Radiant Absorbent for Enhanced Heat Transfer

2019 ◽  
Author(s):  
Hamed Abedini Najafabadi ◽  
Nesrin Ozalp
Keyword(s):  
Heat Transfer ◽  
Elevated Temperatures ◽  
Radiation Heat Transfer ◽  
Carbon Particle ◽  
Subsequent Treatment ◽  
Working Fluid ◽  
Solar Simulator ◽  
Original Activity ◽  
Carbon Particles ◽  
Solar Reactor

Abstract Carbon particles can be used as catalyst in solar reactors where they serve as radiant absorbent and nucleation sites for the heterogeneous decomposition reaction. Unlike commonly used metal catalysts, carbon catalyst does not have durability problem and high cost. However, in order to achieve sustainable catalytic decomposition of feedstock over carbon catalysts at elevated temperatures, the surface area of the carbon particles must be maintained. A subsequent treatment of deactivated carbon samples with CO2 at about 1000°C would increase the surface and would recover the original activity as catalyst. In solar reactor, carbon particles are directly exposed to the high-flux irradiation providing efficient radiation heat transfer directly to the reaction site. Therefore, one of the key parameters to achieve higher conversion efficiencies in solar reactor is the presence and transport of carbon particles. This paper will present impact of carbon use in enhancing the heat transfer inside a solar reactor radiated by a solar simulator. Flux entering the receiver is determined using Monte Carlo ray tracing (MCRT) method which is coupled with energy balance equations to derive numerical model describing dynamic temperature variation in solar receiver. Simulation results indicated that feeding carbon particles results to lower temperatures for the cavity walls and working fluid compare to the case that no carbon is injected. This finding is in accordance with our experimental results obtained from a cylindrical cavity receiver radiated by a 7 kW solar simulator. The results indicated that heat transfer within the system is highly influenced by the particle size. At particle sizes larger than 450 μm, carbon feeding increases the thermal efficiency of the system.

Investigation on the Combustion Rate of Carbon Particle in Pressurized Oxygen-Enriched Conditions

2011 ◽  
Vol 354-355 ◽  
pp. 380-384
Author(s):  
Chun Bo Wang ◽  
Jin Gui Sheng ◽  
Ming Lei ◽  
Jian Guo Wei ◽  
Xiao Fei Ma
Keyword(s):  
Particle Size ◽  
Combustion Rate ◽  
Carbon Particle ◽  
Enriched Environment ◽  
Carbon Particles

The combustion rates of carbon particle in pressurized oxygen-enriched environment were studied. The combustion rates of different diameter carbon particles were calculated in atmospheric as well as pressurized oxygen-enriched conditions. The effects of pressure and particle size on combustion rate of carbon particle were investigated. It shows that the combustion rate of carbon particle rise with the increase of the pressures in pressurized oxygen-enriched and pressurized air conditions. But, the combustion rate of carbon particle change little at higher pressure. When particle size increased from 50μm to 100μm，the combustion rate of carbon particle rising. When the particle size increased to 150μm, the combustion rate of carbon particle changed little.

A Computational Fluid Dynamics Study on the Effect of Carbon Particle Seeding for the Improvement of Solar Reactor Performance

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
Nesrin Ozalp ◽  
Anoop Kanjirakat
Keyword(s):  
Flow Reactor ◽  
Carbon Particle ◽  
Decomposition Reaction ◽  
Reactor Performance ◽  
Injection Point ◽  
Carbon Particles ◽  
Solar Reactor ◽  
Lagrangian Framework ◽  
Nucleation Sites ◽  
Window Screening

This study focuses on a technique, referred to as “solar cracking” of natural gas for the coproduction of hydrogen and carbon as byproduct with zero emission footprint. Seeding a solar reactor with micron-sized carbon particles increases the conversion efficiency drastically due to the radiation absorbed by the carbon particles and additional nucleation sites formed by carbon particles for heterogeneous decomposition reaction. The present study numerically tries to investigate the above fact by tracking carbon particles in a Lagrangian framework. The results on the effect of particle loading, particle emissivity, injection point location, and effect of using different window screening gases on a flow and temperature distribution inside a confined tornado flow reactor are presented.

Heat Transfer Model of a 50 kW Solar Receiver–Reactor for Thermochemical Redox Cycling Using Cerium Dioxide

2019 ◽  
Vol 141 (2) ◽  
Author(s):  
S. Zoller ◽  
E. Koepf ◽  
P. Roos ◽  
A. Steinfeld
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Solar Radiation ◽  
Cerium Dioxide ◽  
Input Power ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Solar Reactor ◽  
Concentrated Solar Radiation ◽  
Solar Receiver

This work reports on the development of a transient heat transfer model of a solar receiver–reactor designed for thermochemical redox cycling by temperature and pressure swing of pure cerium dioxide in the form of a reticulated porous ceramic (RPC). In the first, endothermal step, the cerium dioxide RPC is directly heated with concentrated solar radiation to 1500 °C while under vacuum pressure of less than 10 mbar, thereby releasing oxygen from its crystal lattice. In the subsequent, exothermic step, the reactor is repressurized with carbon dioxide as it cools, and at temperatures below 1000 °C, the partially reduced cerium dioxide is re-oxidized with a flow of carbon dioxide. To analyze the performance of the solar reactor and to gain insight into improved design and operational conditions, a transient heat transfer model of the solar reactor for a solar radiative input power of 50 kW during the reduction step was developed and implemented in ANSYS cfx. The numerical model couples the incoming concentrated solar radiation using Monte Carlo ray tracing, incorporates the reduction chemistry by assuming thermodynamic equilibrium, and accounts for internal radiation heat transfer inside the porous ceria by applying effective heat transfer properties. The model was experimentally validated using data acquired in a high-flux solar simulator (HFSS), where temperature evolution and oxygen production results from model and experiment agreed well. The numerical results indicate the prominent influence of solar radiative input power, where increasing it substantially reduces reduction time of the cerium dioxide structure. Consequently, the model predicts a solar-to-fuel energy conversion efficiency of >6% at a solar radiative power input of 50 kW; efficiency >10% can be obtained provided the RPC macroporosity is substantially increased, and better volumetric absorption and uniform heating is achieved. Managing the ceria surface temperature during reduction to avoid sublimation is a critical design consideration for direct absorption solar receiver–reactors.

Prediction of the Flow, Reaction and Heat Transfer for Glass Furnace Firing Petroleum Coke

2013 ◽  
Vol 690-693 ◽  
pp. 3090-3096
Author(s):  
Chang Sheng Hu ◽  
Yun Bo Wang ◽  
Ping Wang ◽  
Jian Quan Bi
Keyword(s):  
Heat Transfer ◽  
Computer Simulation ◽  
Particle Size ◽  
Mathematical Models ◽  
Petroleum Coke ◽  
Glass Furnace ◽  
Gas Dynamics ◽  
Dispersed Phase ◽  
Operation Condition ◽  
Simulation Results

In this paper, the mathematical models of gas dynamics, combustion and heat transfer and dispersed phase were established for the glass furnace combustion space, according to the practical glass furnace and operation condition, the computer simulation of the glass furnace was made; the simulation results coincided with the facts. On the base the influence of particle size of petroleum coke and oxygen-enriched combustion on the furnace combustion has been simulated.

An Investigation of the Distribution of Trihalomethanes Within GAC Contactors

1987 ◽  
Vol 22 (3) ◽  
pp. 412-426
Author(s):  
R.C. Andrews ◽  
P.M. Huck ◽  
L. Gammie
Keyword(s):  
Particle Size ◽  
Drinking Water ◽  
Activated Carbon ◽  
Organic Carbon ◽  
Total Organic Carbon ◽  
Carbon Particle ◽  
Pilot Scale ◽  
Carbon Particles ◽  
Enhanced Adsorption ◽  
Different Sources

Abstract This study examined the loading distribution of trihalomethanes and total organic carbon within pilot scale granular activated carbon (GAC) contactors receiving finished drinking water and operating in the downflow mode. Three carbons originating from different sources were used for this comparison. Observed column loadings were compared to isotherms. As well, loadings were evaluated as a function of carbon particle size. Significantly higher loadings of trihalomethanes were found in the upper 10 cm (7%) of the GAC beds. Enhanced adsorption in this region was correlated with finer size carbon particles. Isotherms successfully predicted full bed depth trihalomethane loadings for two of the carbons but underestimated loadings in the top 10 cm. A replacement of the top 30 cm of the carbon in one of the beds resulted in a noticeable capacity increase for trihalomethanes.

Interfacial Thermal Resistance Between a Carbon Nanoparticle and Molten Salt Eutectic: Effect of Material Properties, Particle Shapes and Sizes

2011 ◽  
Author(s):  
Byeongnam Jo ◽  
Debjyoti Banerjee
Keyword(s):  
Particle Size ◽  
Thermal Resistance ◽  
Molten Salt ◽  
Thermal Power ◽  
Carbon Particle ◽  
Interfacial Thermal Resistance ◽  
Graphite Sheet ◽  
Carbon Particles ◽  
Different Shapes ◽  
Particle Shapes

The aim of this study is to estimate the interfacial thermal resistance between a carbon nano-particle and alkali molten salt eutectics using molecular dynamics simulations. Additionally the effect of particle shapes and sizes on the interfacial thermal resistance was investigated using three different shapes of the carbon nanoparticles. Transient heat transfer simulation between a carbon particle and molecules of a molten salt was performed with the lumped capacitance method. A carbonate salt eutectic which consists of lithium carbonate (Li2CO3) and potassium carbonate (K2CO3) in 62:38 molar ratio was used as a solvent medium for the nanoparticles. Three carbon particles of a single walled carbon nanotube (SWNT), a fullerene (C60), and a graphite sheet were used to represent different shapes of cylinders, a spheres, and disks, respectively. The interfacial thermal resistance was determined by a correlation with a specific heat of the carbon particle, their surface area, and the time constant of decaying particle temperature. The results show the interfacial thermal resistance values are independent of the particle size for SWNT and graphite particles. For three carbon particles with a similar particle size, similar resistances were obtained in our simulations. The purpose of this study is to design and develop novel high-temperature Thermal Energy Storage (TES) materials in order to improve the operational efficiencies for harnessing solar thermal power at cheaper costs for Concentrated Solar Power (CSP) systems.

scholarly journals Jet Impingement Heat Transfer of Confined Single and Double Jets with Non-Newtonian Power Law Nanofluid under the Inclined Magnetic Field Effects for a Partly Curved Heated Wall

2021 ◽  
Vol 13 (9) ◽  
pp. 5086
Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Oztop ◽  
Ali J. Chamkha
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Particle Size ◽  
Aspect Ratio ◽  
Power Law ◽  
Volume Fraction ◽  
Inclined Magnetic Field ◽  
Magnetic Field Effects ◽  
Power Law Nanofluid ◽  
Power Law Index

Single and double impinging jets heat transfer of non-Newtonian power law nanofluid on a partly curved surface under the inclined magnetic field effects is analyzed with finite element method. The numerical work is performed for various values of Reynolds number (Re, between 100 and 300), Hartmann number (Ha, between 0 and 10), magnetic field inclination (γ, between 0 and 90), curved wall aspect ratio (AR, between 01. and 1.2), power law index (n, between 0.8 and 1.2), nanoparticle volume fraction (ϕ, between 0 and 0.04) and particle size in nm (dp, between 20 and 80). The amount of rise in average Nusselt (Nu) number with Re number depends upon the power law index while the discrepancy between the Newtonian fluid case becomes higher with higher values of power law indices. As compared to case with n = 1, discrepancy in the average Nu number are obtained as −38% and 71.5% for cases with n = 0.8 and n = 1.2. The magnetic field strength and inclination can be used to control the size and number or vortices. As magnetic field is imposed at the higher strength, the average Nu reduces by about 26.6% and 7.5% for single and double jets with n greater than 1 while it increases by about 4.78% and 12.58% with n less than 1. The inclination of magnetic field also plays an important role on the amount of enhancement in the average Nu number for different n values. The aspect ratio of the curved wall affects the flow field slightly while the average Nu variation becomes 5%. Average Nu number increases with higher solid particle volume fraction and with smaller particle size. At the highest particle size, it is increased by about 14%. There is 7% variation in the average Nu number when cases with lowest and highest particle size are compared. Finally, convective heat transfer performance modeling with four inputs and one output is successfully obtained by using Adaptive Neuro-Fuzzy Interface System (ANFIS) which provides fast and accurate prediction results.

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