Search

Simultaneous measurement of liquid film characteristics and heat transfer in annular two-phase flow is a major experimental challenge. In this study, we implement an innovative integrated infrared (IR) heater and liquid film electrical-conductance sensor in combination with high-speed IR thermography, which results in an accurate, synchronized and co-located measurement of liquid film characteristics and local heat transfer at the heated surface in diabatic annular two-phase flow. The measurements reveal that disturbance waves have a significant effect on the instantaneous heat transfer response in nominally-steady vertically upward annular flow of steam-water mixtures. Although the heat flux applied at the wall is constant in time, the passage of the waves causes significant periodic oscillations of the local heat transfer coefficient and wall superheat in the forced convective evaporation regime, which are reported in this study.

Accident-tolerant fuels (ATFs) are currently of high interest to researchers in the nuclear industry and in governmental and international organizations. One widely studied accident-tolerant fuel concept is multilayer cladding (also known as coated cladding). This concept is based on a traditional Zr-based alloy (Zircaloy-4, M5, E110, ZIRLO etc.) serving as a substrate. Different protective materials are applied to the substrate surface by various techniques, thus enhancing the accident tolerance of the fuel. This study focuses on the results of testing of Zircaloy-4 coated with pure chromium metal using the cold spray (CS) technique. In comparison with other deposition methods, e.g., Physical vapor deposition (PVD), laser coating, or Chemical vapor deposition techniques (CVD), the CS technique is more cost efficient due to lower energy consumption and high deposition rates, making it more suitable for industry-scale production. The Cr-coated samples were tested at different conditions (500°C steam, 1200°C steam, and Pressurized water reactor (PWR) pressurization test) and were precharacterized and postcharacterized by various techniques, such as scanning electron microscopy, Energy-dispersive X-ray spectroscopy (EDX), or nanoindentation; results are discussed. Results of the steady-state fuel performance simulations using the Bison code predicted the concept's feasibility. It is concluded that CS Cr coating has high potential benefits but requires further optimization and out-of-pile and in-pile testing., United States. Department of Energy (Grant DE-NE0008416)

Nucleation, growth, and detachment of steam bubbles during nucleate boiling of a water pool at atmospheric pressure is experimentally investigated using a combination of synchronized high-speed video, infrared thermography, and particle image velocimetry. The heater is a thin (< 1-μm), horizontal (20 × 10 mm[superscript 2]), resistively heated, indium-tin-oxide film, vacuum deposited on a sapphire substrate (250-μm thick), which allows for unobstructed optical access from below the boiling surface. This approach enables detailed measurement of the phase, temperature, and velocity distributions on and above the boiling surface. The database reported herein is for isolated bubbles, exhibiting nucleation temperatures 107–109°C, bubble departure diameters 3.0–3.8 mm, frequencies 4.7–15.00 Hz, and wait and growth times 52–200 ms and 15–16 ms, respectively, at average heat fluxes 29–36 kW/m[superscript 2]. The database is most useful for validation of modern simulations of nucleate boiling in which the phase, temperature, and velocity distributions within and around bubbles are resolved using interface capturing methods such as volume of fluid, level set, and front tracking., United States. Dept. of Energy (Consortium for Advanced Simulation of LWRs), National Science Foundation (U.S.). Graduate Research Fellowship Program

Nucleate boiling is important in many energy systems including light water reactors. Currently significant efforts are underway to develop mechanisticmodels for nucleate boiling based on computational fluid dynamics (CFD). Development and validation of these models require new high fidelity experimental data with high spatial and temporal resolutions. Previous work such as has measured temperature distributions and diameter of a growing bubble. It is important to obtain further information, such as bubble shape during growth and after departure, and velocity profiles in the liquid.This paper presents an improved experimental approach for synchronized measurement of these data.