Critical heat flux (CHF) and post-CHF are two critical phenomena in light water-cooled nuclear power plants regarding safety. Even though the general trends of CHF and post- CHF are known, the exact mechanisms are still unknown. To better understand CHF and post-CHF, experimental flow boiling facilities are constructed around the world. However, these facilities are limited in their experimental conditions and spatial resolution necessary to advance our understanding of two-phase heat transfer. Previous rod surface measurements were collected with thermocouples to measure CHF location and temperature excursion, yet thermocouples provide limited spatial resolution, which leads to significant uncertainties in the CHF prediction. On the other hand, optical fiber temperature sensors can measure the temperature and the CHF propagation with high spatial resolution. Also, the capability of the optical fiber at high temperatures has been proven in previous studies. The current study aims to apply optical fiber at high-pressure and high mass fluxes. The high-Pressure HIgh-temperature annuLUS flow (PHILUS) facility was designed to provide desired working conditions in the test section that uses optical fiber temperature sensors. The PHILUS test section has a length of 1320 mm, with 1000 mm of heated length. The working conditions of the PHILUS are up to 18 MPa, temperatures up to 357◦C, and coolant mass flux from 500 to 3700 kg/m2s. The main components of the loop are a steam separator, two heat exchangers (a condenser and a cooler), a bladder-type accumulator, two bypass lines, and a high-pressure pump. Coolant-Boiling in Rod Arrays-Two Fluids (COBRA-TF) code was used to design the CHF and post-CHF experiments to be performed at the PHILUS facility. / Master of Science / A nuclear power plant produces heat which is transferred from the reactor core through the coolant. The coolant water flows through the reactor core to safely transport the heat that ultimately is used to produce electrical energy. If the balance between the power produced by fission and the energy removed by the coolant is changed, it can lead to potential damage to the reactor core. The maximum heat transfer rate occurs at the point where a vapor blanket covers the surface of the fuel cladding. At this point, known as Critical Heat Flux (CHF), the surface temperature drastically increases. To better understand and better predict the CHF, experimental facilities are needed. Even though there are several facilities worldwide, most of them have limited working conditions and measurement capabilities. Past experiments used thermocouples to measure the surface temperature with a very small spatial resolution, which causes very large uncertainties in the CHF and post-CHF predictions. On the other hand, optical fiber sensors can be used to measure temperature with very high spatial resolution. The high-Pressure HIgh-temperature annuLUS flow (PHILUS) facility was designed in this work to apply optical fibers in the measurement of the rod surface temperature and simulations were performed to show its advantages. The working conditions of the PHILUS are comparable to commercial pressurized water reactors.

abstract: This study identifies the influence that leading-edge shape has on the aerodynamic characteristics of a wing using surface far-field and near-field analysis. It examines if a wake survey is the appropriate means for measuring profile drag and induced drag. The paper unveils the differences between sharp leading-edge and blunt leading-edge wings with the tools of pressure loop, chordwise pressure distribution, span load plots and with wake integral computations. The analysis was performed using Computational Fluid Dynamics (CFD), vortex lattice potential flow code (VORLAX), and a few wind-tunnels runs to acquire data for comparison. This study found that sharp leading-edge wings have less leading-edge suction and higher drag than blunt leading-edge wings. The blunt leading-edge wings have less drag because the normal vector of the surface in the front section of the airfoil develops forces at opposed skin friction. The shape of the leading edge, in conjunction with the effect of viscosity, slightly alter the span load; both the magnitude of the lift and the transverse distribution. Another goal in this study is to verify the veracity of wake survey theory; the two different leading-edge shapes reveals the shortcoming of Mclean’s equation which is only applicable to blunt leading-edge wings. / Dissertation/Thesis / Masters Thesis Aerospace Engineering 2019