Chenn Q. Zhou

2.45 GHz radiofrequency fields alter gene expression in cultured human cells

The biological effect of radiofrequency (RF) fields remains controversial. We address this issue by examining whether RF fields can cause changes in gene expression. We used the pulsed RF fields at a frequency of 2.45 GHz that is commonly used in telecommunication to expose cultured human HL‐60 cells. We used the serial analysis of gene expression (SAGE) method to measure the RF effect on gene expression at the genome level. We observed that 221 genes altered their expression after a 2‐h exposure. The number of affected genes increased to 759 after a 6‐h exposure. Functional classification of the affected genes reveals that apoptosis‐related genes were among the upregulated ones and the cell cycle genes among the downregulated ones. We observed no significant increase in the expression of heat shock genes. These results indicate that the RF fields at 2.45 GHz can alter gene expression in cultured human cells through non‐thermal mechanism.

Numerical Study of Spray Injection Effects on the Heat Transfer and Product Yields of FCC Riser Reactors

A three-phase reacting flow computational fluid dynamics (CFD) computer code was used to study the major effects of spray injection parameters on mixing, heat transfer, vaporization, and reaction product yields in fluidized catalytic cracking (FCC) riser reactors. The CFD code was validated using experimental or field data. A number of computations were performed with varied injection parameters, including injection velocity, injection angle, and droplet size. Local optimum operating windows for spray injection parameters were identified, and the sensitivity of local optima to variation in spray parameters was also investigated.

CFD Simulation of a Hydrogen Reformer Furnace

A hydrogen reformer furnace is a combustion chamber which is used to supply heat for the catalytic process that converts natural gas into hydrogen. The reforming reaction that happens inside the catalyst tubes is endothermic, requiring high levels of heat input. The combustion process in the hydrogen reformer furnace provides the heat to maintain the chemical reaction inside the catalyst tubes. Temperature control of the catalyst tubes is a fundamental design requirement of the hydrogen reformer furnace, as the temperature should be maintained in the range which could maximize catalyst reactivity while minimizing any damage to the catalyst pipes. As the furnace has two complicated chemical systems, the heat effect inside the tubes has been simplified by estimating the heat flux based on industry operation. Utilizing the multiphase and non-premixed combustion model using CFD (Computational Fluid Dynamic), the temperature and velocity distribution in the hydrogen reformer furnace have been investigated. Results show that parts of the catalyst tubes are overheated causing hot spots which could lead to premature aging of the pipes. Both the location of burners and maldistribution of the hot flue gas have a great impact on this issue.Copyright

Evaluation of stock profile models for burden distribution in blast furnace

Burden distribution in a blast furnace is vital to its smooth running. Mathematical models have been applied to guide the charging process to achieve desired burden distribution. The accuracies of such models depend on the prediction of falling curve, stock profile and burden descent mode. Among them, the stock profile model greatly influences the final burden distribution. In this study, a special evaluation index for the accuracy of the modelled burden profile based on charging volume is established. Six existing stock profile models were evaluated and compared with the published experiment data of a scaled blast furnace. It is found that all the models predicted the stock profile well. However, certain models showed increased accuracy for the particular case.

Numerical Methods for Simulating the Reduction of Iron Ore in Blast Furnace Shaft

The blast furnace process is a counter-current moving bed chemical reactor to reduce iron oxides to iron, which involves complex transport phenomena and chemical reactions. The iron ore and coke are alternatively charged into the blast furnace, forming a layer by layer structural burden which is slowly descending in the counter-current direction of the ascending gas flow. A new methodology was proposed to efficiently simulate the gas and solid burden flow in the counter-current moving bed in blast furnace shaft. The gas dynamics, burden movement, chemical reactions, heat and mass transfer between the gas phase and solid phase are included. The new methodology has been developed to explicitly consider the effects of the layer thickness thermally and chemically in the CFD model. [DOI: 10.1115/1.4025946]

Parametric Studies on PCI Performances

The pulverized coal injection (PCI) is widely utilized in the iron-making blast furnaces for its economic and environmental advantages. However, due its complexity, flow dynamics and chemical kinetics of PCI inside the raceway has not been well understood. Combustions of PCI and coke inside the raceway can be influenced by tuyere operation parameters. In this paper, a comprehensive three dimensional (3-D) multiphase flow computational fluid dynamics (CFD) model was utilized to investigate the PCI and coke combustion in the lower part of a blast furnace. Systematic parametric studies were conducted to analyze the effects of the natural gas injection, coal injection, PCI rate, and oxygen enrichment on the combustion performance, which include coal burnt-out rate, coke consumption rate, raceway shape, raceway temperature and etc.Copyright

A Methodology for Blast Furnace Hearth Inner Profile Analysis

The wear of a blast furnace hearth and the hearth inner profile are highly dependent on the liquid iron flow pattern, refractory temperatures, and temperature distributions at the hot face. In this paper, the detailed methodology is presented along with the examples of hearth inner profile predictions. A new methodology along with new algorithms is proposed to calculate the hearth erosion and its inner profile. The methodology is to estimate the hearth primary inner profile based on 1D heat transfer and to compute the hot-face temperature using the 3D CFD hearth model according to the 1D preestimated and reestimated profiles. After the hot-face temperatures are converged, the hot-face positions are refined by a new algorithm, which is based on the difference between the calculated and measured results, for the 3D computational fluid dynamics (CFD) hearth model further computations, until the calculated temperatures well agree with those measured by the thermocouples.

Control of NOx emissions by NOx recycle approach

NO3 recycle is an alternative approach for the control of NOx emissions from combustion. It uses regenerable sorbent to adsorb NOx in the flue gas from a combustor followed by desorption, producing a highly concentrated NOx-laden stream containing both NO and NO2. This stream is then sent back to the same combustor or to a separate combustor, where the NOx is reduced in the flame and NO3 formation is inhibited. Experimental studies have been performed to investigate the effect of NOx recycle on the reduction of NOx emissions. Highly concentrated NO. NO2, or NO/NO2 mixtures were recycled into a combustor at different locations. It has been found that a range of 50–90% of NOx reduction efficiency could be achieved depending on experimental conditions. The NOx reduction efficiency in the combustor is affected by the recycle location, the amount of exit air, and the composition of recycle gases. The most favorable recycle location is at the primary air duct. When NOx is recycled into the secondary air duct, the lower the exit O2, the better for the NOx destruction in the flame. The experimental results also indicated higher NOx reduction efficiency for the NO2 recycle in comparison with the NO recycle. The concept of the NOx recycle approach has been implemented in the NOXSO process, which is a dry, postcombustion flue gas treatment technology for fossil-fueled boilers that can remove more than 90% of NOx/SO2. The NOx recycle approach is expected to be a new alternative for NOx removal from flue gas, especially for integrated systems that use regenerable sorbent to simultaneously remove NOx, SO2, and other pollutants emitted from combustion.

Computational Fluid Dynamics Analysis of 3D Hot Metal Flow Characteristics in a Blast Furnace Hearth

The campaign life of an iron blast furnace depends on hearth wear. Distributions of liquid iron flow and refractory temperatures have a significant influence on hearth wear. A 3D comprehensive computational fluid dynamics model has been developed specifically for simulating the blast furnace hearth. It includes both the hot metal flow and the conjugate heat transfer through the refractories. The model has been extensively validated using measurement data from Mittal Steel old, new IH7 blast furnace and U.S. Steel 13 blast furnace. Good agreements between measured and calculated refractory temperature profiles have been achieved. It has been used to analyze the velocity and temperature distributions and wear patterns of different furnaces and operating conditions. The results can be used to predict the inner profile of hearth and to provide guidance for protecting the hearth.

CFD Modeling of Flow and Heat Transfer Inside a Liquid-Cooled Exhaust Manifold

Liquid cooled exhaust manifolds are used in turbo charged diesel and gas engines in the marine and various industrial applications. Performance of the manifold has a significant impact on the engine efficiency. Modifying manifold design and changing operational parameters are ways to improve its performance. With the rapid advance of computer technology and numerical methods, Computational Fluid Dynamics (CFD) has become a powerful tool that can provide useful information for manifold optimization. In this study, commercial CFD software (FLUENT® ) was used to analyze liquid cooled exhaust manifolds. Detailed information of flow property distribution and heat transfer were obtained in order to provide a fundamental understanding of the manifold operation. Experimental data was compared with the CFD results to validate the numerical simulation. Computations were performed to investigate the parametric effects of operating conditions (engine rotational speed, coolant flow rate, coolant inlet temperature, exhaust gas inlet temperature, surface roughness of the manifold’s material) on the performance of the manifold. Results were consistent with the experimental observations. Suggestions were made to improve the manifold design and performance.© 2003 ASME