Carbon Particle Generation and Preliminary Small Particle Heat Exchange Receiver Lab Scale Testing

2013 ◽  
Author(s):  
Lee Frederickson ◽  
Kyle Kitzmiller ◽  
Fletcher Miller
Keyword(s):  
High Temperature ◽  
Heat Exchange ◽  
Natural Gas ◽  
Small Particle ◽  
Carbon Particle ◽  
Solar Flux ◽  
Gas Mixture ◽  
Solar Simulator ◽  
Spherical Cap ◽  
Carbon Particles

High temperature central receivers are on the forefront of concentrating solar power research. Current receivers use liquid cooling and power steam cycles, but new receivers are being designed to power gas turbine engines within a power cycle while operating at a high efficiency. To address this, a lab-scale Small Particle Heat Exchange Receiver (SPHER), a high temperature solar receiver, was built and is currently undergoing testing at the San Diego State University’s (SDSU) Combustion and Solar Energy Laboratory. The final goal is to design, build, and test a full-scale SPHER that can absorb 5 MWth and eventually be used within a Brayton cycle. The SPHER utilizes air mixed with carbon particles generated in the Carbon Particle Generator (CPG) as an absorption medium for the concentrated solar flux. Natural gas and nitrogen are sent to the CPG where the natural gas undergoes pyrolysis to carbon particles and nitrogen is used as the carrier gas. The resulting particle-gas mixture flows out of the vessel and is met with dilution air, which flows to the SPHER. The lab-scale SPHER is an insulated steel vessel with a spherical cap quartz window. For simulating on-sun testing, a solar flux is produced by a solar simulator, which consists of a 15kWe xenon arc lamp, situated vertically, and an ellipsoidal reflector to obtain a focus at the plane of the receiver window. The solar simulator has been shown to produce an output of about 3.25 kWth within a 10 cm diameter aperture. Inside of the SPHER, the carbon particles in the inlet particle-gas mixture absorb radiation from the solar flux. The carbon particles heat the air and eventually oxidize to carbon dioxide, resulting in a clear outlet fluid stream. Since testing was initiated, there have been several changes to the system as we have learned more about the operation. A new extinction tube was designed and built to obtain more accurate mass loading data. Piping and insulation for the CPG and SPHER were improved based on observations between testing periods. The window flange and seal have been redesigned to incorporate window film cooling. These improvements have been made in order to achieve the lab scale SPHER design objective gas outlet flow of 650°C at 5 bar.

Carbon Particle Generation and Lab-Scale Small Particle Heat Exchange Receiver Experimentation and Modeling

2014 ◽  
Author(s):  
Lee Frederickson ◽  
Mario Leoni ◽  
Fletcher Miller
Keyword(s):  
Heat Exchange ◽  
Computer Model ◽  
Small Particle ◽  
Carbon Nanoparticles ◽  
Carbon Particle ◽  
Rankine Cycle ◽  
Gas Temperature ◽  
Solar Simulator ◽  
Ansys Fluent ◽  
Carbon Particles

Central receivers being installed in recent commercial CSP plants are liquid-cooled and power a steam turbine in a Rankine cycle. San Diego State University’s (SDSU) Combustion and Solar Energy Laboratory has built and is testing a lab-scale Small Particle Heat Exchange Receiver (SPHER). The SPHER is an air-cooled central receiver that is designed to power a gas turbine in a Brayton cycle. The SPHER uses carbon nanoparticles suspended in air as an absorption medium. The carbon nanoparticles should oxidize by the outlet of the SPHER, which is currently designed to operate at 5 bar absolute with an exit gas temperature above 1000°C. Carbon particles are generated from hydrocarbon pyrolysis in the carbon particle generator (CPG). The particles are mixed at the outlet of the CPG with dilution air and the mixture is sent to the SPHER. As the gas-particle mixture flows through the SPHER, radiation entering the SPHER from the solar simulator is absorbed by the carbon particles, which transfer heat to the gas suspension and eventually oxidize, resulting in a clear gas stream at the outlet. Particle mass loading is measured using a laser opacity measurement combined with a Mie calculation, while particle size distribution is determined by scanning electron microscopy and a diesel particulate scatterometer prior to entering the SPHER. In predicting the performance of the system, computer models have been set up in CHEMKIN-PRO for the CPG and in ANSYS Fluent for the SPHER, which is coupled with VeGaS ray trace code for the solar simulator. Initial experimentation has resulted in temperatures above 850°C with around a 50K temperature difference when particles are present in the air flow. The CPG computer model has been used to estimate performance trends while the SPHER computer model has been run for conditions to match those expected from future experimentation.

Study on Properties of Carbon Particle Modified Silicon Carbide Composite Ceramics

2011 ◽  
Vol 311-313 ◽  
pp. 276-282 ◽  
Author(s):  
You Jun Lu ◽  
Hong Fang Shen ◽  
Yan Ming Wang
Keyword(s):  
Silicon Carbide ◽  
High Temperature ◽  
Carbon Particle ◽  
Composite Ceramics ◽  
Carbon Particles ◽  
High Temperature Mechanical Properties ◽  
Sic Ceramics ◽  
Carbide Composite ◽  
Application Fields ◽  
Different Content

High-temperature mechanical properties, machinability, oxidation resistance and thermal shock resistance of different content of carbon particles modified silicon carbide composite ceramics (Cp/SiC) prepared by pressureless sintering techniques were studied. Adhesion of Cp/SiC to melted glass under 1000°C was also observed. The results showed that 15-Cp/SiC had the optimum machinability and it also did not adhere to melted glass at high temperature. And flexural strength, hardness, and fracture toughness of 15-Cp/SiC is 136.5MPa, 274.6kgf/mm2, 2.58MPa•m1/2 respectively. The good performance of Cp/SiC made it possible to be used as high temperature glass fixture, which means that Cp/SiC can not only improve the service life of fixture materials, but also broaden the application fields of SiC ceramics.

Oxidation Rate Analysis of Carbon Nanoparticles for a Small Particle Heat Exchange Receiver

2014 ◽  
Author(s):  
Mario Leoni ◽  
Lee Frederickson ◽  
Fletcher Miller
Keyword(s):  
Heat Exchange ◽  
Small Particle ◽  
Oxidation Rate ◽  
Flow Behavior ◽  
Average Diameter ◽  
Index Of Refraction ◽  
Spherical Particles ◽  
Extinction Cross Section ◽  
Carbon Particles ◽  
Rate Analysis

A new experimental set-up has been introduced at San Diego State University’s Combustion and Solar Energy Lab to study the thermal oxidation characteristics of in-situ generated carbon particles in air at high pressure. The study is part of a project developing a Small Particle Heat Exchange Receiver (SPHER) utilizing concentrated solar power to run a Brayton cycle. The oxidation data obtained will further be used in different existing and planned computer models in order to accurately predict reactor temperatures and flow behavior in the SPHER. The carbon black particles were produced by thermal decomposition of natural gas at 1250 °C and a pressure of 5.65 bar (82 psi). Particles were analyzed using a Diesel Particle Scatterometer (DPS) and scanning electron microscopy (SEM) and found to have a 310 nm average diameter. The size distribution and the complex index of refraction were measured and the data were used to calculate the specific extinction cross section γ of the spherical particles. The oxidation rate was determined using 2 extinction tubes and a tube furnace and the values were compared to literature. The activation energy of the carbon particles was determined to be 295.02 kJ/mole which is higher than in comparable studies. However, the oxidation of carbon particles bigger than 100 nm is hardly studied and almost no previous data is available at these conditions.

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.

High-Temperature Carbon Particle Formation and Decay in Carbon Suboxide Pyrolysis behind Shock Waves

2000 ◽  
Vol 214 (1) ◽  
Author(s):  
J. Deppe ◽  
A. Emelianov ◽  
A. Eremin ◽  
H. Jander ◽  
H.Gg. Wagner ◽  
...  
Keyword(s):  
High Temperature ◽  
Shock Waves ◽  
Carbon Particle ◽  
Particle Formation ◽  
Carbon Suboxide ◽  
Carbon Particles

The formation of carbon particles following the pyrolysis of C

Developing the Small Particle Heat Exchange Receiver for a Prototype Test

2012 ◽  
Author(s):  
Fletcher J. Miller ◽  
Arlon J. Hunt
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Natural Gas ◽  
Solar Radiation ◽  
Small Particle ◽  
Thermal Power ◽  
Index Of Refraction ◽  
Nano Particles ◽  
Prototype Test ◽  
Concentrated Solar Radiation

The concept of absorbing concentrated solar radiation volumetrically, rather than on a surface, is being researched by several groups with differing designs for high temperature solar receivers. The Small Particle Heat Exchange Receiver (SPHER), one such design, is a gas-cooled central receiver capable of producing pressurized air in excess of 1100 C designed to be directly integrated into a Brayton-cycle power block to generate electricity from solar thermal power. The unique heat transfer fluid used in the SPHER is a low-density suspension of carbon nano-particles (diameter ∼ 200 nm) to absorb highly concentrated solar radiation directly in a gas stream, rather than on a fixed absorber like a tube or ceramic foam. The nano-particles are created on-demand by pyrolyzing a small flow of natural gas in an inert carrier gas just upstream of the receiver, and the particle stream is mixed with air prior to injection into the receiver. The receiver features a window (or multiple windows, depending on scale) on one end to allow concentrated sunlight into the receiver where it is absorbed by the gas-particle suspension prior to reaching the receiver walls. As they pass through the receiver the carbon nano-particles oxidize to CO2 resulting a clear gas stream ready to enter a downstream combustor or directly into the turbine. The amount of natural gas consumed or CO2 produced is miniscule (1–2%) compared to what would be produced if the natural gas were burned directly to power a gas turbine. The idea of a SPHER, first proposed many years ago, has been tested on a kW scale by two different groups. In the new work, the engineering for a multi-MW SPHER is reported. An in-house Monte Carlo model of the radiation heat transfer in the gas-particle mixture has been developed and is coupled to FLUENT to perform the fluid dynamic calculations in the receiver. Particle properties (size distribution and complex index of refraction) are obtained experimentally from angular scattering and extinction measurements of natural gas pyrolysis in a lab-scale generator, and these are corroborated using image analysis of Scanning Electron Microscope (SEM) pictures of particles captured on a filter. A numerical model of the particle generator has been created to allow for scale-up for a large receiver. We have also designed a new window for the receiver that will allow pressurized operation up to 10 bar with a 2 m diameter window. Recent progress on overcoming the engineering challenges in developing this receiver for a prototype test is reported.

HAYNES STELLITE ALLOY No. 4

Alloy Digest ◽  
1969 ◽  
Vol 18 (11) ◽  
Keyword(s):  
Fracture Toughness ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Physical Properties ◽  
Cast Alloy ◽  
Heat Treating ◽  
Carbon Particles ◽  
Stellite Alloy ◽  
Temperature Performance ◽  
Cobalt Base

Abstract Haynes Stellite No. 4 is a cobalt-base cast alloy recommended for handling severe conditions of abrasion, heat and corrosion. It is especially recommended to resist the severe abrasive and corrosive action of manganese dioxide, carbon particles, and ammonium and zinc chlorides in the battery mix used in the manufacture of dry batteries. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on high temperature performance and corrosion resistance as well as heat treating, machining, and joining. Filing Code: Co-59. Producer or source: Union Carbide Materials Systems Division.

Design of a New 45 kWe High-Flux Solar Simulator for High-Temperature Solar Thermal and Thermo-Chemical Research

2010 ◽  
Author(s):  
Katherine R. Krueger ◽  
Jane H. Davidson ◽  
Wojciech Lipin´ski
Keyword(s):  
High Temperature ◽  
Focal Plane ◽  
Flux Distribution ◽  
Solar Thermal ◽  
Optimized Design ◽  
High Flux ◽  
Chemical Research ◽  
Solar Simulator ◽  
Peak Flux ◽  
The Common

In this paper, we present a systematic procedure to design a solar simulator for high-temperature concentrated solar thermal and thermo-chemical research. The 45 kWe simulator consists of seven identical radiation units of common focus, each comprised of a 6.5 kWe xenon arc lamp close-coupled to a precision reflector in the shape of a truncated ellipsoid. The size and shape of each reflector is optimized by a Monte Carlo ray tracing analysis to achieve multiple design objectives, including high transfer efficiency of radiation from the lamps to the common focal plane and desired flux distribution. Based on the numerical results, the final optimized design will deliver 7.5 kW over a 6-cm diameter circular disc located in the focal plane, with a peak flux approaching 3.7 MW/m2.

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