Yitung Chen
University of Nevada, Las Vegas, Mechanical Engineering, Faculty Member
Research Interests:
Clark County, Nevada has been criticized by US Environmental Protection Agency (US EPA) for its un-attainment air quality problem for particulate matters (PM 10 and PM 2.5) and ozone (O3) and carbon monoxide (CO). The Department of Air... more
Clark County, Nevada has been criticized by US Environmental Protection Agency (US EPA) for its un-attainment air quality problem for particulate matters (PM 10 and PM 2.5) and ozone (O3) and carbon monoxide (CO). The Department of Air Quality Management (DAQM), Clark County, the regulatory and enforcement agency, is required by the US EPA to measure and report to the public the impact of aeroallergens as well as visibility and haze issues. From the long-term observation, air quality in the Las Vegas Valley is also influenced by those pollution from the neighboring states, currently around 30 monitoring stations through out the county have been in service for years to continuously monitor meteorological condition and provide valuable air quality information to the public in a timely fashion. Since the existing monitoring system was not designed to collect and process large amount of data set at a short time period, the agency cannot flexibly acquire higher resolution data sets as we...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
In this paper, we propose several solar cell designs based on metamaterials. Extensive numerical simulations of various designs with different materials are carried out. Our tests show that metamaterial solar cells are quite efficient,... more
In this paper, we propose several solar cell designs based on metamaterials. Extensive numerical simulations of various designs with different materials are carried out. Our tests show that metamaterial solar cells are quite efficient, and over 80% and 90% absorption rates can be attained for solar spectrum and visible rays, respectively.
Research Interests:
Research Interests:
ABSTRACT
Research Interests:
ABSTRACT
Research Interests:
ABSTRACT A solid particle solar receiver (SPSR) is a direct absorption central receiver that uses solid particles enclosed in a cavity to absorb concentrated solar radiation. However, the existing open aperture lowers the overall... more
ABSTRACT A solid particle solar receiver (SPSR) is a direct absorption central receiver that uses solid particles enclosed in a cavity to absorb concentrated solar radiation. However, the existing open aperture lowers the overall efficiency by convection heat transfer. Aerowindows have the potential of increasing the efficiency of an SPSR by reducing convective losses from an open receiver aperture and eliminate reflection, convection and reradiation losses from a comparable glass window. Aerodynamic windows consist of a transparent gas stream, which is injected from an air jet, across the receiver aperture to isolate its interior from the surrounding atmosphere. Even though, the wind conditions may still have important effect on the performance of SPSRs. In the present paper, the wind effect on the performance of an SPSR is investigated numerically. The mass, momentum and energy exchange between the solid particle and air flow are simulated by the two-way coupling Euler-Lagrange method in the realizable k-ε turbulence 3D model. The independence of the calculating domain is studied in order to select a proper domain for the numerical simulation. Solar ray tracing method is employed in calculating the solar radiation energy. The numerical investigation of the performance of the SPSR is focusing on optimizing the prototype design and finding out the best working condition for the SPSR. In order to investigate the influences of the wind speed and wind blowing direction on the performance of the receiver, different wind conditions of and different air jet injection conditions are simulated numerically. The cavity thermal efficiencies are calculated and the optimal injection conditions are analyzed for different wind conditions.
Research Interests:
ABSTRACT
Research Interests:
ABSTRACT
Research Interests:
Ceramics are suitable for use in high temperature applications as well as corrosive environment. These characteristics were the reason behind selection silicone carbide for a high temperature heat exchanger and chemical decomposer, which... more
Ceramics are suitable for use in high temperature applications as well as corrosive environment. These characteristics were the reason behind selection silicone carbide for a high temperature heat exchanger and chemical decomposer, which is a part of the Sulphur-Iodine (SI) thermo-chemical cycle. The heat exchanger is expected to operate in the range of 950°C. The proposed design is manufactured using fused ceramic layers that allow creation of micro-channels with dimensions below one millimeter. A proper design of the heat exchanges requires considering possibilities of failure due to stresses under both steady state and transient conditions. Temperature gradients within the heat exchanger ceramic components induce thermal stresses that dominate other stresses. A three-dimensional computational model is developed to investigate the fluid flow, heat transfer and stresses in the decomposer. Temperature distribution in the solid is imported to finite element software and used with pre...
Research Interests:
The recent developments in the energy industry have kindled renewed interest in producing energy more efficiently. This has motivated the development of higher temperature cycles and their associated equipment. In this paper we will... more
The recent developments in the energy industry have kindled renewed interest in producing energy more efficiently. This has motivated the development of higher temperature cycles and their associated equipment. In this paper we will discuss several design configurations coupled with the inherent properties of preferred ceramic materials to assess the viability and design reliability of ceramic heat exchangers for next generation high temperature heat exchangers. These analyses have been extended to conceptually compare the traditional shell and tube heat exchanger with shell and plate heat exchangers. These analyses include hydrodynamic, heat transfer, mechanical stress and reliability models applicable to an Intermediate Heat Exchanger (IHX) and Process Coupling Heat Exchangers. It was found that ceramic micro-channel heat exchanger designs proved to have the greatest reliability due to their inherent mechanical properties, minimal thermo-mechanical stresses while improving the per...
Research Interests:
This paper presents the results obtained from a series of experiments that have been conducted on a 150kW pf burner rig based at Casella CRE Ltd. in the United Kingdom. These experiments systematically varied the burner swirl number and... more
This paper presents the results obtained from a series of experiments that have been conducted on a 150kW pf burner rig based at Casella CRE Ltd. in the United Kingdom. These experiments systematically varied the burner swirl number and the secondary air flow rate over a significant range for two different coals so that both satisfactory and ‘poor’ combustion conditions were obtained. The infra-red emissions from the flame and the combustion noise generated in the furnace chamber were measured with appropriate sensors as were the fuel and air flow rates and pollutant emissions. The signals from the sensors were analysed using signal processing techniques to yield a number of features. These in turn were employed to train a neural network to accurately estimate the gaseous emissions from the rig, such as NOx and CO. In a separate set of experiments, where the combustion process was placed in a poor condition, the sensors were coupled with the neural models and incorporated into an in...
Research Interests:
Research Interests: Mechanical Engineering, Chemical Engineering, Applied Mathematics, Materials Science, Heat Exchangers, and 8 moreSulfur, Thermal Decomposition, HYDROGEN AS A FUEL, Sustainability, Hydrogen As Fuel for Engines, Mechanical Engineering and heat and mass transfer, Sulfuric Acid, and Thermochemical Cycle
Research Interests: Materials Engineering, Mechanical Engineering, Nuclear Engineering, Condensed Matter Physics, Materials Science, and 13 moreChemistry, Computational Materials Science, Materials Science and Engineering, Model, High Temperature, Finite Difference, Oxidation, High Temperatures, Weight Gain, Liquid metals, Volume change, metal flow, and Descaling
Research Interests: Materials Engineering, Mechanical Engineering, Nuclear Engineering, Condensed Matter Physics, Materials Science, and 11 moreChemistry, Computational Materials Science, Cellular Automata, Materials Science and Engineering, Mesoscopic Physics, Model, Diffusion, Oxide, Oxidation, Eutectics, and Cellular automaton
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
It is of interest to perform experiments that simulate some aspects of the response of a high-level radioactive waste repository to episodic water flows. While exact analogies of the physical situation are impossible to represent in... more
It is of interest to perform experiments that simulate some aspects of the response of a high-level radioactive waste repository to episodic water flows. While exact analogies of the physical situation are impossible to represent in experiments, some physical effects can be examined in unsaturated flows. Of particular concern here is the temperature and humidity conditions achieved within a heated annulus in a porous medium subjected to a transient water flow. A 38.1 mm x 304.8 mm x 304.8 mm (high) block of rigid porous material has been used. This block has a 25.4 mm diameter electrical heater mounted horizontally in a 38.1 mm diameter hole, transversely penetrating the block. Thermocouples and humidity sensors are mounted at various locations within the medium and in the annulus. Results are reported for studied that are initiated after the dry material has reached a steady-state temperature distribution with the heater at a predetermined temperature. One of two fixed amounts of water is poured on the top surface of the porous medium and the effects of the water flow on the thermocouple and humidity sensor readings are reported.
Research Interests:
Research Interests:
ABSTRACT The flow over a backward facing step is a classic problem in applied aerodynamics. Among many other applications, backward facing steps are often used for ignition and stabilization of the flame in a scramjet engine. In this... more
ABSTRACT The flow over a backward facing step is a classic problem in applied aerodynamics. Among many other applications, backward facing steps are often used for ignition and stabilization of the flame in a scramjet engine. In this study, the steady two-dimensional viscous supersonic turbulent flow over a backward facing step was calculated using FLUENT. The one-equation Spalart and Allmaras turbulence model was employed for the turbulent flow simulation. The free stream Mach number was 2. The simulated flow field is in good qualitative agreement with flow visualizations, pressure and temperature measurements and theoretical predictions. The boundary layer ahead of the step turns through the right angle over the corner. Then a separation occurs below the corner on the step wall. The numerical results indicate that the separation point is positioned on the step face, below the corner. The overexpansion at the corner is balanced by a lip-shock. This phenomenon was observed in experimental measurements, in flow visualizations and is also obtained in the present numerical calculation.
Research Interests:
Research Interests:
Research Interests:
A model is developed and analyses are conducted to analyze the casting of metallic fuels pins. The important physics of the model includes the flow of the melt into the mold, the heat transfer into the mold, the amount of preheating in... more
A model is developed and analyses are conducted to analyze the casting of metallic fuels pins. The important physics of the model includes the flow of the melt into the mold, the heat transfer into the mold, the amount of preheating in the mold, and the rate of heat transfer from the melt to the mold. This paper discusses and presents preliminary modeling results for the casting of long, slender fuel rods. Parametric modeling results are presented and discussed.
Research Interests:
Research Interests:
Research Interests: Materials Science, Heat Transfer, Heat Exchanger, Failure Analysis, Catalyst, and 15 moreStress analysis, Computer Model, Silicon Carbide, Iodine, Hydrogen Production, Chemical Analysis, High Temperature, Nuclear reactor, Fluid flow, Sulfur, Chemical Reaction, Stress Analysis, Sulfur Dioxide, Parametric analysis, and Parametric Study
This article describes a compact silicon carbide ceramic, high-temperature heat exchanger for hydrogen production in the sulfur iodine thermo-chemical cycle; and in particular, to be used as the sulfuric acid decomposer. In this cycle,... more
This article describes a compact silicon carbide ceramic, high-temperature heat exchanger for hydrogen production in the sulfur iodine thermo-chemical cycle; and in particular, to be used as the sulfuric acid decomposer. In this cycle, hot helium from a nuclear reactor is used to heat the SI (sulfuric acid) feed components (H2O, H2SO4, SO3) to obtain appropriate conditions for the SI
Research Interests: Mechanical Engineering, Applied Mathematics, Materials Science, Heat Exchanger, Failure Analysis, and 15 moreCeramics, Stress analysis, Silicon Carbide, Hydrogen Production, High Temperature, Nuclear reactor, Numerical Model, HYDROGEN AS A FUEL, Stress Analysis, Sulfur Dioxide, Chemical Engineering Heat & Mass Transfer, Hydrogen As Fuel for Engines, Mechanical Engineering and heat and mass transfer, Sulfuric Acid, and Parametric Study
Research Interests:
Research Interests:
Research Interests:
ABSTRACT
Research Interests:
Research Interests:
Research Interests:
ABSTRACT
Research Interests:
A detailed three-dimensional computational fluid dynamics (CFD) analysis on gas-particle flow and heat transfer inside a solid-particle solar receiver, which utilizes free-falling particles for direct absorption of concentrated solar... more
A detailed three-dimensional computational fluid dynamics (CFD) analysis on gas-particle flow and heat transfer inside a solid-particle solar receiver, which utilizes free-falling particles for direct absorption of concentrated solar radiation, is presented. The two-way coupled Euler-Lagrange method is implemented and includes the exchange of heat and momentum between the gas phase and solid particles. A two-band discrete ordinate method is included to investigate radiation heat transfer within the particle cloud and between the cloud and the internal surfaces of the receiver. The direct illumination energy source that results from incident solar radiation was predicted by a solar load model using a solar ray-tracing algorithm. Two kinds of solid-particle receivers, each having a different exit condition for the solid particles, are modeled to evaluate the thermal performance of the receiver. Parametric studies, where the particle size and mass flow rate are varied, are made to determine the optimal operating conditions. The results also include detailed information for the gas velocity, temperature, particle solid volume fraction, particle outlet temperature, and cavity efficiency.
Research Interests: Mechanical Engineering, Computational Fluid Dynamics, Modeling, Heat Transfer, Performance, and 13 moreAlgorithm, Dimensional Analysis, Solar Energy, Diffusion, Computation Fluid Dynamics, Temperature, Ray Tracing, Solar radiation, Particulate Matter, Interdisciplinary Engineering, Solar Energy Engineering, Parametric analysis, and Heat Radiation
ABSTRACT
Research Interests:
ABSTRACT