scholarly journals Experimental Evaluation of Using Silica Aerogels as the Thermal Insulator for Combustor Liners

2020 ◽  
Vol 4 ◽  
pp. 202-216
Author(s):  
Yeongmin Pyo ◽  
Taylor Robertson ◽  
Sean Yun ◽  
Zekai Hong
Keyword(s):  
Temperature Distribution ◽  
Silica Aerogel ◽  
Silica Aerogels ◽  
Transpiration Cooling ◽  
Back Side ◽  
Flow Rates ◽  
Thermal Insulator ◽  
Metal Liner ◽  
Combustion Tests ◽  
Cooling Air

An experimental study was conducted for evaluating the feasibility of using silica aerogel as thermal insulator for combustor liners. Aerogels are a superior material for minimizing heat flux to the metal structure of the combustion liner due to their low thermal conductivity. In this study, a conical natural gas fired swirling-flame combustor was utilized for reproducing the combustion environment. The silica aerogel blanket was attached to the inner side of a perforated combustor liner. Temperature distribution on the outer side of the combustion liner was measured using a calibrated IR camera. To create a protective cooling film over the aerogel surface, cooling air was supplied from the back side of the perforated metal liner and was allowed to penetrate the silica aerogel blanket to be discharged to the combustor. As the combustor was operated at a fixed equivalence ratio of 0.83, cooling air flow rates were varied to evaluate the effectiveness of transpiration cooling on the aerogel blanket as various cooling flow rates. The measured evolution of temperature distribution confirmed thermal equilibriums for every test condition with transpiration cooling. The measured temperature distribution of metal liner demonstrated superior thermal insulation of aerogel blanket under the protection of cooling film with a temperature difference as high as 1580 K between combustion products temperature and the metal liner temperature on the back side. In addition, silica aerogel samples were examined before and after the combustion tests to understand their material degradation exposing to a typical gas turbine combustor environment using high-resolution scanning electron microscope (SEM). Test results suggest multiple degradation mechanisms to the silica aerogel blanket samples from the combustion tests. Improvements can be made to the silica aerogel blankets for a more resilient thermal insulator, for example, by replacing glass fibers in silica aerogels.

scholarly journals Temperature log simulations in high-enthalpy boreholes

2019 ◽  
Vol 7 (1) ◽  
Author(s):  
Jia Wang ◽  
Fabian Nitschke ◽  
Maziar Gholami Korzani ◽  
Thomas Kohl
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Temperature Gradient ◽  
Flow Rate ◽  
Fluid Loss ◽  
Flow Conditions ◽  
Flow Rates ◽  
High Enthalpy ◽  
Fluid Losses ◽  
Lateral Heat

Abstract Temperature logs have important applications in the geothermal industry such as the estimation of the static formation temperature (SFT) and the characterization of fluid loss from a borehole. However, the temperature distribution of the wellbore relies on various factors such as wellbore flow conditions, fluid losses, well layout, heat transfer mechanics within the fluid as well as between the wellbore and the surrounding rock formation, etc. In this context, the numerical approach presented in this paper is applied to investigate the influencing parameters/uncertainties in the interpretation of borehole logging data. To this end, synthetic temperature logs representing different well operation conditions were numerically generated using our newly developed wellbore simulator. Our models account for several complex operation scenarios resulting from the requirements of high-enthalpy wells where different flow conditions, such as mud injection with- and without fluid loss and shut-in, occur in the drill string and the annulus. The simulation results reveal that free convective heat transfer plays an important role in the earlier evolution of the shut-in-time temperature; high accuracy SFT estimation is only possible when long-term shut-in measurements are used. Two other simulation scenarios for a well under injection conditions show that applying simple temperature correction methods on the non-shut-in temperature data could lead to large errors for SFT estimation even at very low injection flow rates. Furthermore, the magnitude of the temperature gradient increase depends on the flow rate, the percentage of fluid loss and the lateral heat transfer between the fluid and the rock formation. As indicated by this study, under low fluid losses (< 30%) or relatively higher flow rates (> 20 L/s), the impact of flow rate and the lateral heat transfer on the temperature gradient increase can be ignored. These results provide insights on the key factors influencing the well temperature distribution, which are important for the choice of the drilling data to estimate SFT and the design of the inverse modeling scheme in future studies to determine an accurate SFT profile for the high-enthalpy geothermal environment.

scholarly journals Silica Aerogel Monoliths Derived from Silica Hydrosol with Various Surfactants

Molecules ◽  
2018 ◽  
Vol 23 (12) ◽  
pp. 3192 ◽  
Author(s):  
Dong Chen ◽  
Xiaodong Wang ◽  
Wenhui Ding ◽  
Wenbing Zou ◽  
Qiong Zhu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Stability ◽  
Silica Aerogel ◽  
Low Cost ◽  
Ambient Pressure ◽  
Silica Aerogels ◽  
Ambient Pressure Drying ◽  
Low Thermal Conductivity ◽  
Silica Hydrosol ◽  
High Production Cost

Owing to their ultra-low thermal conductivity, silica aerogels are promising thermal insulators; however, their extensive application is limited by their high production cost. Thus, scientists have started to explore low-cost and easy preparation processes of silica aerogels. In this work, a low-cost method was proposed to prepare silica aerogels with industrial silica hydrosol and a subsequent ambient pressure drying (APD) process. Various surfactants (cationic, amphoteric, or anionic) were added to avoid solvent exchange and surface modification during the APD process. The effects of various surfactants on the microstructure, thermal conductivity, and thermal stability of the silica aerogels were studied. The results showed that the silica aerogels prepared with a cationic or anionic surfactant have better thermal stability than that prepared with an amphoteric surfactant. After being heated at 600 °C, the silica aerogel prepared with a cationic surfactant showed the highest specific surface area of 131 m2∙g−1 and the lowest thermal conductivity of 0.038 W∙m−1∙K−1. The obtained low-cost silica aerogel with low thermal conductivity could be widely applied as a thermal insulator for building and industrial energy-saving applications.

Numerical Modeling and Design of an Inspection Device with Thermoelectric Coolers for the Coke Oven

2009 ◽  
Vol 419-420 ◽  
pp. 29-32 ◽  
Author(s):  
Tung-Hsin Yeh ◽  
Jiin Yuh Jang ◽  
Yu Bin Chen ◽  
Der Her Wang
Keyword(s):  
Numerical Modeling ◽  
High Temperature ◽  
Temperature Distribution ◽  
Necessary Conditions ◽  
Three Dimensional ◽  
Coke Oven ◽  
Thermoelectric Coolers ◽  
Thermal Insulator ◽  
Wall Condition ◽  
Cooling Element

In order to inspect on wall condition inside the coke oven, an inspection device has been developed to protect a camera inside and sustains high temperature long enough so that it can be permanently-installed on the pusher ram beam. The temperature of the coking chamber during operation is about 1200 °C while the maximum tolerable temperature of a camera is less than 40 °C. The device has to function as a good thermal insulator with cooling element for the camera at the pusher head and for signal cables along the beam. In this paper, the necessary conditions of the inspective device were found out by building a three-dimensional numerical model of the device to simulate the temperature distribution inside the device with CFD commercial software.

Preparation of Silica Aerogels Monoliths from Hydrophobic Silica Gels and Pluronic10R5 via Sol–Gel Process

2020 ◽  
Vol 12 (2) ◽  
pp. 206-211
Author(s):  
Supattra Eangpayung ◽  
Supan Yodyingyong ◽  
Darapond Triampo
Keyword(s):  
Mass Loss ◽  
Propylene Oxide ◽  
Silica Aerogel ◽  
Sol Gel ◽  
Silica Aerogels ◽  
Silica Gels ◽  
High Porosity ◽  
Hydrophobic Silica ◽  
Sol Gel Process ◽  
Poly Propylene

Silica aerogel, the most common type of aerogels, comprised of 95% air in its structure which made the aerogel has a high surface area, high porosity, low density, and low thermal conductivity. Because of its structure and high porosity, one of its major weakness compared to other materials is being very brittle. This study aims at strengthening the connection points between silica nanoparticles using Pluronic10R5 (poly(propylene oxide)8–poly(ethylene oxide)22–poly(propylene oxide)8) where the Pluronic10R5 was used to reduce phase separation during the silica condensation reaction in the sol–gel process. Silica aerogel monoliths were prepared via a sol–gel process from hydrophobic silica gels and Pluronic10R5 with an ambient pressure drying (APD) process. Results from the compression test showed that the Pluronic10R5/silica aerogels have improved mechanical property by ten times that of unmodified silica aerogels. A thermogravimetric analysis (TGA) showed a mass loss at 300–400 °C that is attributed to the surface methyl group, while a mass loss at 200 °C refers to the loss of Pluronic10R5 which confirms the incorporation of Pluronic10R5 into the monolith. Moreover, infrared (IR) images revealed that the top surface temperature of Pluronic10R5/silica aerogels monolith is about 80 °C differs from the bottom heat source temperature of 160 °C.

Preparation and Characterization of Ultralow Density Silica Aerogels by Acetonitrile Supercritical Drying

2012 ◽  
Vol 519 ◽  
pp. 83-86 ◽  
Author(s):  
Guang Wu Liu ◽  
Xing Yuan Ni ◽  
Bin Zhou ◽  
Qiu Jie Yu
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Silica Aerogel ◽  
Sol Gel ◽  
Supercritical Drying ◽  
Silica Aerogels ◽  
High Specific Surface Area ◽  
Molar Ratio ◽  
Sol Gel Process

This paper deals with the synthesis of ultralow density silica aerogels using tetramethyl orthosilicate (TMOS) as the precursor via sol-gel process followed by supercritical drying using acetonitrile solvent extraction. Ultralow density silica aerogels with 6 mg/cc of density was made for the molar ratio by this method. The microstructure and morphology of the ultralow density silica aerogels was characterized by the specific surface area, SBET, SEM, and the pore size distribution techniques. The results show that the ultralow density silica aerogel has the high specific surface area of 812m2/g. Thermal conductivities at desired temperatures were analyzed by the transient plane heat source method. Thermal conductivity coefficients of silica aerogel monoliths changed from 0.024 to 0.043W/ (m K) as temperature increased to 400°C, revealed an excellent heat insulation effect during thermal process.

Sample Retention in the Transport Tubing between an Electrothermal Vaporizer and an Inductively Coupled Plasma Mass Spectrometer

1996 ◽  
Vol 50 (1) ◽  
pp. 86-90 ◽  
Author(s):  
Christopher M. Sparks ◽  
James A. Holcombe ◽  
Thomas L. Pinkston
Keyword(s):  
Temperature Distribution ◽  
Mass Spectrometer ◽  
Inductively Coupled Plasma ◽  
Total Mass ◽  
Maximum Power ◽  
Flow Rates ◽  
Argon Gas ◽  
Inductively Coupled ◽  
Transport Tube

The transport tube between a commercial electrothermal vaporizer (ETV) and the torch for an inductively coupled plasma mass spectrometer ICPMS) was analyzed for sample that had been vaporized. A common analyte carrier, NaCl, and Ag were the primary samples analyzed. It was found that approximately 10% of the sample was retained in the transport tubing. This percentage could be varied by changing the total mass of sample vaporized, probably because of the smaller particles being formed. A temperature distribution of the argon gas in the transport tube was also obtained for maximum power heating of the ETV, for a one-second vaporization step, and for various flow rates.

Airflow and Cooling in a Data Center

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Suhas V. Patankar
Keyword(s):  
Fluid Dynamics ◽  
Data Center ◽  
Cfd Simulations ◽  
Flow Rates ◽  
Factors Affecting ◽  
Hot Air ◽  
Airflow Distribution ◽  
Computational Fluid Dynamics Cfd ◽  
Cooling Air ◽  
Insight Into

This paper deals with the distribution of airflow and the resulting cooling in a data center. First, the cooling challenge is described and the concept of a raised-floor data center is introduced. In this arrangement, cooling air is supplied through perforated tiles. The flow rates of the cooling air must meet the cooling requirements of the computer servers placed next to the tiles. These airflow rates are governed primarily by the pressure distribution under the raised floor. Thus, the key to modifying the flow rates is to influence the flow field in the under-floor plenum. Computational fluid dynamics (CFD) is used to provide insight into various factors affecting the airflow distribution and the corresponding cooling. A number of ways of controlling the airflow distribution are explored. Then attention is turned to the above-floor space, where the focus is on preventing the hot air from entering the inlets of computer serves. Different strategies for doing this are considered. The paper includes a number of comparisons of measurements with the results of CFD simulations.

scholarly journals Synthesis of Silicon Carbide Powders from Methyl-Modified Silica Aerogels

2020 ◽  
Vol 10 (18) ◽  
pp. 6161
Author(s):  
Kyoung-Jin Lee ◽  
Yanggu Kang ◽  
Young Hun Kim ◽  
Se Won Baek ◽  
Haejin Hwang
Keyword(s):  
Silicon Carbide ◽  
High Purity ◽  
Silica Aerogel ◽  
Carbothermal Reduction ◽  
Single Phase ◽  
Phase Evolution ◽  
Silica Aerogels ◽  
Methyl Groups ◽  
Modified Silica ◽  
Lower Temperature

β-silicon carbide (SiC) powders were synthesized by the carbothermal reduction of methyl-modified silica aerogel/carbon mixtures. The correlations between the phase evolution and morphologies of the SiC powders and the C/SiO2 ratio were investigated. At a C/SiO2 ratio of 3, β-SiC formed at 1425 °C and single-phase SiC powders were obtained at 1525 °C. The methyl groups (-CH3) on the silica aerogel surfaces played important roles in the formation of SiC during the carbothermal reduction. SiC could be synthesized from the silica aerogel/carbon mixtures under lower temperature and C/SiO2 ratios than those needed for quartz or hydrophilic silica. The morphology of the SiC powder depended on the C/SiO2 ratio. A low C/SiO2 ratio resulted in β-SiC powder with spherical morphology, while agglomerates consisting of fine SiC particles were obtained at the C/SiO2 ratio of 3. High-purity SiC powder (99.95%) could be obtained with C/SiO2 = 0.5 and 3 at 1525 °C for 5 h.

Local Measurements of Disk Heat Transfer in Heated Rotating Cavities for Several Flow Regimes

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
André Günther ◽  
Wieland Uffrecht ◽  
Stefan Odenbach
Keyword(s):  
Heat Flux ◽  
Flow Regimes ◽  
Local Heat ◽  
Heat Fluxes ◽  
Flow Structures ◽  
Back Side ◽  
Wide Range ◽  
Toroidal Vortices ◽  
Axial Heat ◽  
Cooling Air

This paper discusses experimental results from a two-cavity test rig representation of the internal air system of a high-pressure compressor. Thermal steady-state measurements of the time-averaged local heat fluxes on both sides of the middle disk are presented for three different flow regimes: pure axial throughflow of cooling air and axial throughflow of cooling air in two directions with a superposed radial inflow of hot air in one cavity. Mass flow ratios between 1/40 < mrad/max < 2/1 are measured. Tests were carried out for a wide range of non-dimensional parameters: Reφ up to 107, Rez up to 2 × 105, and Cw up to −2.5 × 104. In all cases, the shroud is uniformly heated to approximately 100 °C. The local axial heat fluxes are determined separately for both sides of the middle disk from measurements of the surface temperatures with open spot-welded thermo-couples. The method of heat flux determination and an analysis approach calculating the uncertainties and the sensitivity are described and discussed. The local heat flux results of the different flow paths are compared and interpreted by assumed flow structures. The time-averaged heat flux results can be adequately interpreted by flow structures of two toroidal vortices for axial throughflow and a source-sink flow for the radial inflow. The measurements show that the axial heat flux can change direction, i.e., areas exist where the disk is heated and not cooled by the flow. For axial throughflow, a local minimum of heat flux exists on the impinged side in the range of x = 0.65. On the back side, a heating area exists in all tests in the lower half of the disk (x < 0.6) due to recirculated air of higher temperature. This heating area corresponds to the range of the inner vortex and increases with higher axial and rotational Reynolds numbers.

Combustion System Update SGT5-4000F: Design, Testing and Validation

2013 ◽  
Author(s):  
Boris F. Kock ◽  
Bernd Prade ◽  
Benjamin Witzel ◽  
Holger Streb ◽  
Mike H. Koenig
Keyword(s):  
Gas Turbines ◽  
High Reliability ◽  
Product Development Process ◽  
Test Facility ◽  
Combustion System ◽  
Lean Premixed Combustion ◽  
Air Mixing ◽  
Acoustic Stability ◽  
Combustion Tests ◽  
Cooling Air

The first Siemens AG SGT5-4000F engine with hybrid burner ring combustor (HBR) was introduced in 1996. Since then, frequent evolutionary design improvements of the combustion system were introduced to fulfill the continuously changing market requirements. The improvements particularly focused on increased thermodynamic performance, reduced emissions, and increasing operational flexibility in terms of load gradients, fuel flexibility, and turndown capability. According to the Siemens product development process, every design evolution had to pass several validation steps to ensure high reliability and best performance. The single steps included cold flow and mixing tests at atmospheric pressure, high-pressure combustion tests in full-scale sector combustion test rigs, and full engine tests at the Berlin test facility (BTF). After successful validation, the design improvements were gradually released for commercial operation. In a first step, cooling air reduction features have been implemented in 2005, followed by the introduction of a premixed pilot as second step in 2006. Both together resulted in a significant reduction of the NOx emissions of the system. In a third step, an aerodynamic burner modification was introduced in 2007, which improved the thermo-acoustic stability of the system towards higher turbine inlet temperatures and adapted to fuel preheating to allow for increased cycle efficiency. All three features together have been released as package in 2010 and to date accumulated more than 50,000 operating hours (fleet leader 24,000). This paper reports upon the steps towards this latest design status of the SGT5-4000F and presents results from typical focus areas of lean premixed combustion systems in gas turbines including aero-dynamical optimization, fuel/air mixing improvements and cooling air management in the combustor.

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