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This thesis presents the analysis of flow and heat transfer for the SPND (Self-Powered Neutron Detector) system used within the nuclear reactor core in the U.S. Evolutionary Power Reactor developed by AREVA. The SPND system is composed of six individual detectors which are used for in-core measurement of thermal neutron flux. The study of the SPND system is important since this system provides information and signals necessary for safe reactor operation and control. The main goal of the project was to determine the maximum temperature for the SPND detectors under three different operating scenarios. The maximum temperature of the detectors is of special interest, since if it exceeds a limiting temperature of 622 K then the accuracy of the information provided by the system is reduced. All of the flow and heat transfer simulations were performed using the commercial software Fluent. The first scenario that was studied was for the system under normal operating conditions. For this case, the maximum temperature for a detector was determined to be 603.4 K, which is within the proper range of operation. It was also important to determine the maximum temperature of the fluid within the SPND assembly in order to ascertain that boiling does not occur within the system during normal operation. The maximum fluid temperature was found to be 613.7 K, which is below the boiling temperature of water (618.05 K) at an operating pressure of 2250 psi. The second scenario involved an increase in the power of the reactor's core by a factor of 17% in a 30 second period. The results of the unsteady calculation indicated that the maximum temperature for a detector was 608.5 K. The results also indicate that no boiling occurs inside of the SPND system. The third scenario involved a loss of coolant flow in the SPND system. This reduction in flow rate caused the maximum temperature of the detectors to reach 619.6 K. For this case, boiling occurs within the guide tube and protection tube. / Master of Science

For over forty years, researchers have attempted to refine the Fourier heat equation to model heat transfer in engineering materials. The equation cannot accurately predict temperatures in some applications, such as during transients in microscale (< 10^-12 s) situations. However, even in situations where the time duration is relatively large, the Fourier heat equation might fail to predict observed non-Fourier behavior. Therefore, non-Fourier models must be created for certain engineering applications, in which accurate temperature modeling is necessary for design purposes. In this thesis, we use the Fourier heat equation to create a general non-Fourier, but diffusive, equation that governs the matrix temperature in a composite material. The composite is composed of a matrix with embedded particles. We let the composite materials be governed by Fourier's law and let the heat transfer between the matrix and particles be governed by contact conductance. After we make certain assumptions, we derive a general integro-differential equation governing the matrix temperature. We then non-dimensionalize the general equation and show that our model reduces to that used by other researchers under a special limit of a non-dimensional parameter. We formulate an initial-boundary-value problem in order to study the behavior of the general matrix temperature equation. We show that the thermalization time governs the transition of the general equation from its small-time limit to its large-time limit, which are both Fourier heat equations. We also conclude that our general model cannot accurately describe temperature changes in an experimental sand composite. / Master of Science

Turbine manufacturers continually seek to gain efficiency by increasing operating temperatures well above the maximum temperature of component alloys. This increase in temperature must be accounted for in the cooling of components by examining the heat transfer from these crucial components. This study specifically examines the effect of a contoured endwall on the heat transfer of a scaled-up stator vane. Understanding the three-dimensional effects of contoured endwalls on vane heat transfer can lead to prolonging blade life. The results of a combined experimental and computational study of heat transfer along the surface of a turbine vane that incorporates a contoured endwall are discussed in detail. A commercially available computational fluid dynamics code was used to design a contoured endwall and simulate an engine representative pressure distribution for a turbine vane cascade placed in a low-speed wind tunnel. A significant flow acceleration caused by the contour increased heat transfer over 40% of the vane span compared to the vane far from the contoured endwall. The effects of freestream turbulence with respect to the contour were examined. Results showed a significant increase in heat transfer at elevated freestream turbulence levels at each span location. The effects of the contour were minimal compared to the effects of increased turbulence. The boundary layer transition location moved further upstream with increasing turbulence. Trip wires were used to model the effect of film-cooling holes on the boundary layer development. The heat transfer increased locally at the trip and either remained elevated if the boundary layer remained turbulent or the heat transfer decreased as the boundary layer relaminarized due to flow acceleration. These results are beneficial to turbine manufacturers interested in effective placement of film-cooling holes. / Master of Science

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