SDSU Theses and Dissertationshttp://hdl.handle.net/10211.10/1882017-04-29T03:28:51Z2017-04-29T03:28:51ZA Comparison of the Monte Carlo Method to the Discrete Ordinates Method in FLUENT for Calculating Radiation Heat Transfer in a Particle Solar ReceiverCho, Eugenehttp://hdl.handle.net/10211.3/1892862017-04-06T17:28:17Z2017-04-06T00:00:00ZA Comparison of the Monte Carlo Method to the Discrete Ordinates Method in FLUENT for Calculating Radiation Heat Transfer in a Particle Solar Receiver
Cho, Eugene
The Combustion and Solar Energy Laboratory (C&SEL) at San Diego State University is developing a Small Particle Heat Exchange Receiver (SPHER) to absorb and transfer heat from concentrated solar radiation to a working fluid for a gas turbine. The SPHER is to be used with a Concentrated Solar Power (CSP) system where a heliostat field highly concentrates solar radiation on the optical aperture of the SPHER. A unique carbon nanoparticle gas mixture within the cavity of the SPHER volumetrically absorbs the solar radiation. This research focuses on comparing a Computational Fluid Dynamics (CFD) model using the ANSYS FLUENT Discrete Ordinates (DO) Model and a program developed by the C&SEL which uses a Monte Carlo Ray Trace (MCRT) method to calculate the spatial and directional distribution of radiation for an idealized solar receiver geometry.
Previous research at the C&SEL has shown successful implementation of the MCRT method to calculate the spatial and directional distribution of radiation for an idealized solar receiver geometry. An alternative method for calculating the Radiative Transport Equations (RTE) being considered uses a FORTRAN program, developed by the C&SEL, with the ANSYS FLUENT DO model for calculating the RTE. The methodology used for determining the correct CFD mesh, radiative boundary conditions, optimal number of DO theta and phi discretization, as well as the optical properties of the participating fluid are presented in this thesis.
For a gray semi-diffuse radiative input with absorption the DO and MCRT method calculate a mean outlet temperature and receiver efficiency of 1320 K, 75.1%, 1406 K, and 85.2% respectively. Adding a scattering to the gas-particle mixture, the DO and MCRT method calculate a decrease in the mean outlet temperature of 1286 K, 69.0%, 1383 K, and 80.3% respectively. Using a non-gray radiative input with a 4-band absorption coefficient and linear anisotropic scattering coefficient the DO method calculates a mean outlet temperature of 1328 K and receiver efficiency of 72.0%. The MCRT method calculates a mean outlet temperature of 1410 K and receiver efficiency of 81.7%.
2017-04-06T00:00:00ZNumerical Simulation of Convective Cooling by a Wall Jet along a Convex SurfaceDhingani, Keyuhttp://hdl.handle.net/10211.3/1892852017-04-06T17:25:00Z2017-04-06T00:00:00ZNumerical Simulation of Convective Cooling by a Wall Jet along a Convex Surface
Dhingani, Keyu
In this research the general case of a wall jet on a convex surface is computationally studied to understand the fluid dynamics and heat transfer. The motivation for this project is to cool the window of a high temperature solar receiver below 800oC through convective cooling using a wall jet over it. As the temperature inside the Small Particle Heat Exchange Receiver (SPHER) located at the top of the Solar Tower can reach up to 1000oC, the receiver window made up of quartz glass has the dangers of structural failure if not cooled.
The eventual goal of the computations is to simulate the wall jet flow over a quarter-scale physical model of the solar receiver window available at Combustion & Solar Energy Lab at San Diego State University, so that the experimental results can be compared with the computational results. In this thesis, the first efforts toward that goal are presented.
A 2-D receiver window model is created in FLUENT which has two inlets at either side of window. A grid study on seven 2-D grids is performed using a jet inlet velocity of 1 m/s and inlet nozzle size of 1 mm to achieve mesh independence as well as time-step independence for transient calculations. Laminar and turbulence models are used to perform steady state and transient computational simulations with varying jet inlet velocity but constant inlet nozzle size of 1 mm. The results of the laminar steady state computations are compared with analytical solutions from the literature showing the agreement between the two. Turbulent cases did not converge and more work is needed on them.
A heat transfer analysis is performed with zero jet flow to compare the results achieved by the numerical calculations with analytical results based on conduction heat transfer. Then with the jet flow using laminar model, a heat transfer analysis is done for cooling the window, which has variable heat flux applied over its surface. The result obtained shows that the cooling is achieved near the inlet but there is no cooling at the top, indicating higher inlet speeds are needed.
2017-04-06T00:00:00ZSubject to ChangeGlenn, Sophiehttp://hdl.handle.net/10211.3/1892842017-04-06T17:22:41Z2017-04-06T00:00:00ZSubject to Change
Glenn, Sophie
The thesis project Subject to Change consists of six individual works that are reflective of my understandings of furniture design as a subjective craft. While there are many indicators that help users recognize an object as furniture, the way these indicators are presented to the users has remained fundamentally the same for hundreds of years. Through researching the social history of furniture, and discussing the romanticizing of wood as a material, I wanted to better understand why the presentation of furniture has remained relatively the same for so long, and if it were at all possible to change these presentations without changing the indicators.
To do this, I decided to create pieces that used furniture forms that were familiar to users, such as wooden cabinets and flat wooden surfaces, in combination with steel forms that are derivative of other functional objects, including tools and architectural structures, but are rendered unfamiliar through a change of scale, proportion, and context. The results are fully functional tables and cabinets that are both inviting and remained true to the craft of furniture making (at least in part), but are also precarious in their presentations, and do not necessarily read as functional at first glance.
The exhibition Subject to Change was installed in the University Gallery at San Diego State University, on view from April 25th through May 5th, 2016.
2017-04-06T00:00:00ZDesign, construction, and initial testing of a lab-scale metal-alloy thermal energy storage system for concentrated solar power applicationsCurran, David Jacobhttp://hdl.handle.net/10211.3/1891762017-04-04T00:05:21Z0018-02-06T00:00:00ZDesign, construction, and initial testing of a lab-scale metal-alloy thermal energy storage system for concentrated solar power applications
Curran, David Jacob
Two features of concentrated solar power that will promote widespread adoption are higher operating temperatures and Thermal Energy Storage (TES). Based on previous work with Thermaphase Energy, SDSU is developing the Metal Alloy Thermal Energy Storage System (MATESS), an innovative TES system based on phase change in Al-Si alloys that stores thermal energy at temperatures from 575 to 1414 C, depending on the Al/Si ratio. Before MATESS can be implemented on a large scale, the validity of the concept and design must be proven at lab-scale and computationally.
The thesis starts with a review of concentrated solar power (CSP) and TES, followed by a description of the full-scale MATESS, defining the characteristics needed for simulation in a computational model or lab-scale recreation. The succeeding sections describe the scaling, design, and construction of an apparatus that will be tested at San Diego State University. This apparatus is designed to recreate flow, temperature, pressure, and heat transfer experienced by MATESS using a compressed air line and a burner. The use of the burner in experimental conditions created some unexpected difficulties, so a look at the burner testing as well as alternative options are presented.
The scaled version of the MATTESS storage unit, consist of a single tube where the encapsulated PCM is exposed to high temperature air (up to 1100 °C) at 5 atmospheres of pressure. The apparatus is equipped with thermocouples positioned to read the temperature of the PCM at points along the length of the vessel as well as inlet and outlet temperatures of the air.
The computational model, created in the FLUENT software package, is robust enough to accurately portray the turbulent fluid flow and heat transfer of air through the system, but the solidification and melting algorithm leaves much to be desired when the end goal is to predict thermal storage capabilities of phase-change alloys. The solidification and melting model in FLUENT is driven by a mushy constant that determines whether the solution converges. An evaluation of the mushy constant, as well as the effect of turbulence in the liquid-metal phase of the storage media are evaluated.
Thesis (M.S.) Mechanical Engineering with a Concentration in Energy and Thermofluids
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