bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced Film Cooling Effectiveness by Integration of Horn-Shaped and Cylindrical Holes
Authors: Zhu Rui , Xie Gongnan , Simon Terrence W.
Published: October 2017

In search of improved cooling of gas turbine blades, the thermal performances of two different film cooling hole geometries (horn-shaped and cylindrical) are investigated in this numerical study. The horn-shaped hole is designed from a cylindrical hole by expanding the hole in the transverse direction to double the hole size at the exit. The two hole shapes are evaluated singly and in tandem. The tandem geometry assumes three configurations made by locating the cylindrical hole at three different positions relative to the horn-shaped hole such that their two axes remain parallel to one another. One has the cylindrical hole downstream from the center of the horn-shaped hole, a second has the cylindrical hole to the left of (as seen by the flow emerging from the horn-shaped hole) and at the same streamwise location as the horn-shaped hole (θ = 90°) and the third has an intermediate geometry between those two geometries (downstream and to the left of the horn-shaped hole - θ = 45°). It is shown from the simulation results that the cooling effectiveness values for the θ = 45° and 90° cases are much better than that for θ = 0° (the first case), and the configuration with θ = 45° exhibits the best cooling performance of the three tandem arrangements. These improvements are attributed to the interaction of vortices from the two different holes, which weakens the counter-rotating vortex pairs inherent to film cooling jet to freestream interaction, counteracts with the lift forces, enhances transverse tensile forces and, thus, enlarges the film coverage zone by widening the flow attachment region. Overall, this research reveals that integration of horn-shaped and cylindrical holes provides much better film cooling effectiveness than cases where two cylindrical film cooling holes are applied with the same tandem configuration.
Investigation of Properties of KCl-MgCl2 Eutectic Salt for Heat Transfer and Thermal Storage Fluids in CSP Systems
Authors: Wang Xiaoxin , Xu Xiankun , Elsentriecy Hassan , Gervasio Dominic , Li Peiwen , Li Yuanyuan , Hao Qing , Xiao Bo
Published: October 2017

Eutectic molten salt MgCl2-KClis was considered as a high temperature heat transfer and thermal storage fluid, being able to work at temperatures up to 800 °C for concentrating solar thermal power. Thermophysical properties including vapor pressure, heat capacity, density, viscosity, and thermal conductivity, and the behavior of the corrosion of high temperature nickel-based alloys in the eutectic salt are investigated and reported in this work. Corrosion studies were carried out and measured at a temperature up to 800 °C over a time span of one week to one month. Low corrosion rate was observed for two types of high temperature nickel-based alloys under the environment that the salt is strictly processed to have a very low level of water and oxygen.
Numerical Analysis of Flow and Electric Field Effects on an EHD Enhanced Mini Heat Exchanger
Authors: Zhang Mingkan , Abdelaziz Omar
Published: October 2017

A novel design of a mini heat exchanger utilizing forced convection heat transfer enhancement with electrohydro-dynamic (EHD) technique has been numerically investigated. When a high voltage is applied to a metal wire, air in its vicinity will be ionized and the injected ions will travel towards electrically grounded heat exchanger surfaces, leading to the corona wind. As a result, the corona wind disturbs the heat exchanger boundary layer and thus enhances heat transfer between the heat exchanger surface and its ambient air. A three dimensional numerical model has been developed to evaluate the heat transfer coefficient (HTC) and air side pressure drop of this EHD enhanced mini heat exchanger. Influences of position and size of the wire are evaluated in order to achieve the highest enhancement. In addition, the swirling flow pattern induced by EHD has been studied due to its important role in heat transfer enhancement. The results show a three times increase of HTC enhanced by EHD effect in present design comparing to the one without EHD effect. The most promising result shows an overall heat transfer coefficient equal to 318 W/(m2·K) for a bare tube in cross flow configuration with airside pressure drop of 2.8 Pa.
Diffraction and Polarization Effects in Radiation Heat Transfer: A Case Study
Authors: Mahan J. Robert , Barki Anum R. , Priestley Kory J.
Published: October 2017

The Monte-Carlo ray-trace (MCRT) method is particularly well suited to the optical design of instrumentation in which very small radiant signals must be separated from a strong background. The present contribution explores an important application lying at the intersection of physical optics and radiation heat transfer. Specifically, we consider instruments intended to monitor the planetary energy budget from low earth orbit. To accommodate the increasingly exigent accuracy requirements imposed by the Earth science community, it has become necessary to include effects such as diffraction and polarization that are normally omitted in traditional radiation heat transfer modeling. This requires that the usual concept of a “ray” be extended to include wavelength, a phase angle, and polarization. A realistic instrument concept is considered that fully exercises the ability of such an approach to capture optical effects that are either ignored or assessed “offline” in traditional modeling efforts. Investigated is the range of variation of detector illumination when the effects of the source spectral content, diffraction, and polarization are included.
Experimental Investigation of Flow Laminarization in a Graphite Flow Channel at High Pressure and High Temperature
Authors: Valentín Francisco I. , Artoun Narbeh , Kawaji Masahiro
Published: October 2017

Hot wire anemometer (HWA) measurements of turbulent gas flow have been performed in upward forced convection experiments at pressures ranging from 0.6 MPa to 6.3 MPa and fluid temperatures ranging from 293 K to 673 K. The results are relevant to deteriorated turbulent heat transfer (DTHT) and flow laminarization in strongly heated gas flows which could occur in gas-cooled Very High Temperature Reactors. The HWA signals were analyzed to directly confirm the occurrence of flow laminarization phenomenon due to strong heating. An X-probe was used to collect radial and axial velocity fluctuation data for pressurized air and pure nitrogen flowing through a circular 16.8 mm diameter flow channel in a 2.7 m long graphite test section for local Reynolds numbers varying from 500 to 22,000. Analyses of the Reynolds stresses and turbulence frequency spectra were carried out and used as indicators of laminar, transition or fully turbulent flow conditions. Low Reynolds stresses indicated the existence of laminar or transitional flow until the local Reynolds number reached a large value, ∼11,000 to 16,000, much higher than the conventional Re = 4,000–5,000 for transition to fully turbulent flow encountered in pipe flows. The critical Reynolds number indicating the completion of transition approximately doubled as the pressure was increased from 0.6 MPa to 2.8 MPa.
Characteristics of the Dimensionless Temperature in Tubes With Axial Wall Heat Conduction
Authors: Lin Mei , Li Shi-cong , Xu Xue-fang , Wang Qiu-wang
Published: October 2017

Characteristics of the dimensionless temperature, θ, are performed to investigate in laminar circular tube flow by numerical simulation with the presence of axial heat conduction. A uniform heat flux is imposed on outside wall surface. The smallest inner diameter of circular tube is only 200 μm. The heat transfer and flow can be described by traditional Navier-Stokes and energy equations. The results shows that θ is identical under the condition of different specified heat flux on the outside wall surface at the same Peclet number. Furthermore, the dimensionless temperature at the tube entrance θ(0) is independent on wall thickness, tube material, working fluid and boundary condition. Hence, the dimensionless temperature at the tube entrance θ(0) is only a function of Peclet number and the corresponding correlation of θ(0) in circular tube is obtained from numerical results and validated by other available cases. Moreover, the correlation of θ(0) is also applied with different cross-sectional shapes of heated solid surface when inner diameter of fluid region is not less than 2.0 mm.
Characterization of an Air-PCM Energy Storage Design for Air Handling Unit Applications
Authors: Wert Sarah , Cruickshank Cynthia A. , Groulx Dominic
Published: October 2017

This paper will discuss the characterization of an air-PCM storage design for commercial air handling unit (AHU) applications during winter. The air-PCM storage design consists of two rows of 29 aluminum flat plate containers (0.45 m × 0.35 m × 0.01 m) filled with PCM, vertically aligned leaving an air channel between each plate of 0.011 m wide. The storage device was placed within a closed air loop which conditions the air to the desired testing temperature and velocity. The PCM selected for testing was RT44HC with a melting temperature of 44 °C. This PCM was chosen for its similar properties to other PCMs having lower melting temperatures (in the range of 5 to 18°C) that could be used in actual HVAC application implementation. The system was instrumented and calibrated with Type T thermocouples and a velocity sensor. The system was tested at various inlet temperatures (55°C to 63°C for charging and 12°C to 25°C for discharging) and flow rates. The instantaneous heat transfer rates and total energy storage were calculated for each test from the data collected. The results provide a baseline value for heat transfer rates in a simple air-PCM design, to be used for model validation.
Nanoscale Thermal Radiation Between Coated Spheres
Authors: Czapla Braden , Narayanaswamy Arvind
Published: October 2017

In this work, we present a new formula for the near-field thermal radiative transfer between two spheres. The formula is identical for coated or uncoated spheres and captures the effect of the coatings in the effective Mie reflection coefficients of the spheres. We also numerically demonstrate that silica coated silver spheres transition from silver-like conductance in the far-field to surface phonon polariton dominated silica-like behavior in the extreme near-field.
Modeling of Intramatrix Heat Transfer in Thermal Energy Storage for Asynchronous Cooling
Authors: Helmns Andrea , Carey Van P.
Published: October 2017

In this paper, we investigate sensible and latent heat transfer through heat exchanger matrix structures containing phase change material (PCM) in the interstitial spacing. The heat transfer is driven by a temperature difference between fluid flow passages and the phase change material matrix which experiences sensible heat transfer until it reaches the phase change material fusion point; then it undergoes melting or solidification in order to store, or reject, energy. In prior work, a dimensionless framework was established to model heat transfer in a thermal energy storage (TES) device much like effectiveness-NTU analysis methods for compact heat exchangers. A key difference, however, is that in TES units, the overall heat transfer coefficient, U, within the phase change material matrix varies spatially in the unit and with time during storage or extraction. Determination of a mean U for these processes is a key challenge to applying the effectiveness-NTU analysis to design of a TES unit. This paper assesses and identifies strategies for determining the matrix overall heat transfer coefficient in a TES unit from model predictions or experiments. The sensitivity of the TES energy efficiency to the matrix overall heat transfer coefficient is also explored, and the implications for some typical applications are discussed.
GA-Based Optimization of Compact Plate Heat Exchangers With Manifold-Microchannel Grooves
Authors: Ladeinde Foluso , Alabi Kehinde , Li Wenhai
Published: October 2017

Manifold-microchannel combinations used on heat transfer surfaces have shown the potential for superior heat transfer performance to pressure drop ratio when compared to chevron type corrugations for plate heat exchangers (PHE) [1–4]. However, compared with heat transfer enhancements such as intermating troughs and Chevron corrugations, manifold-microchannels (MM) have several times more variables that influence the heat transfer and pressure drop characteristics, including microchannel width, depth, passes, manifold depth, width, and manifold fin thickness. Previous work has reported on the effects of some of the variables, and provides some models for their effects on thermal and hydraulic performance. The current paper presents a genetic algorithm (GA)-based procedure to analyze the implicit effects of some of the manifold-microchannel variables, and compare the performance of manifold-microchannel plate heat exchangers to those using standard Chevron corrugations. The objective of the present work is to evaluate the performance of manifold-microchannel heat transfer enhancements and demonstrate the potential for using GA-based procedure to optimize the heat exchanger.

This paper also presents the modifications of the standard GA algorithm when applied to the optimization of MM. The resulting GA procedure is particularly well suited to PHEs for several reasons, including the fact that it does not require continuous variables or functional dependence on the design variables. In addition, the computational effort required for the GA technique in our implementation scales linearly, with a scaling coefficient that is significantly less than one, making it economical to analyze PHEs with several variables with degrees of freedom (DOF) with respect to the fitness function. The results of optimizing a manifold-microchannel plate heat exchanger are presented, and the exchanger’s performance is compared to more conventional PHE of the same volume utilizing chevron corrugations. Finally, results from the empirical procedure presented in this paper for a manifold-microchannel are compared with experimental measurements in Andhare [5].
Heat Transfer Enhancement by Criss-Cross Pattern Formed by 45° Angled Rib Turbulators in a Straight Square Duct
Authors: Singh Prashant , Ji Yongbin , Zhang Mingyang , Ekkad Srinath V.
Published: October 2017

The need for higher turbine efficiency has been constantly pushing the turbine inlet temperatures to elevated levels. Hot gas path temperatures are much higher than the typical blade material yield temperature. Efficient internal cooling technologies are required for safe operation of gas turbine. Several internal cooling technologies have been developed in order to enhance the heat transfer from relatively hotter walls of turbine blade. For mid-chord region of turbine blade, rib turbulators are typically installed in multi-pass channels. Rib turbulators trip the boundary layer, induce secondary flows which enhance near wall shear as well as enhance turbulent mixing when they interact with surrounding walls. Research has been carried out on several aspects of rib turbulated passages in order to achieve higher thermal hydraulic performance. Generally, rib turbulators are installed on two opposite walls of serpentine passages in order to enhance heat transfer from both pressure and suction sides of blade through coolant flowing through complicated paths. Typical arrangement of rib turbulators were parallel to each other or having some offset from each other. In the present study, an attempt has been made to arrange 45° angled ribs in a way that they form a Criss-Cross pattern. Two ribbed configurations with Criss-Cross pattern - Inline and staggered, have been studied where the baseline case was smooth duct with no rib turbulators. The effective rib-pitch-to-rib-height ratio (p/e) was 8.6 and rib-height-to-channel-hydraulic diameter ratio (e/dh) was 0.1. The channel had a total length of 20 hydraulic diameters and the rib turbulators were installed at a distance of six hydraulic diameters from the inlet of the test section to allow flow development. Detailed heat transfer coefficients were measured using transient liquid crystal thermography employing 1D semi-infinite conduction model. Globally averaged Nusselt numbers are calculated from the detailed measurements and thermal hydraulic performance of configurations have been reported with respect to Reynolds number. The aim of this study was to develop a cooling configuration which has higher thermal-hydraulic performance compared to other traditional rib configurations. It has been found that the heat transfer characteristics of the inline and staggered configurations were similar to each other and ranged between three times D-B correlation to 2.7 times, for Reynolds number ranging from 30000 to 60000. Inline configuration had relatively lower frictional losses, however the thermal hydraulic performances of both the configurations were similar.
Heat Transfer During Heating and Cooling of a Packed Bed Comprised of Encapsulated Phase Change Material
Authors: West Glen O. , Udell Kent S.
Published: October 2017

Phase change materials (PCMs) are attractive components of thermal energy storage systems due to their high energy densities and the relatively small temperature differences needed for effective charging and discharging. In this study, experimental data were examined in order to better understand energy exchange in packed beds and porous media comprised of solid/liquid phase change capsules. Air was used as the heat transfer fluid; hot air was injected in order to drive the melting process, while cold air was injected to accomplish freezing or solidification of the PCM.

Theory was developed to describe the temperature variations throughout the bed. Temperatures in the bed were found to vary exponentially near the phase change fronts. For cold air injection into a bed initially above the phase change temperature, a second wave was observed ahead of the phase change front that can be described as a broadening traveling thermal wave due to diffusion/dispersion. For hot air injection into a packed bed of solidified PCM capsules initially at a temperature below the phase change temperature, the thermal waves in the cold region showed isotherm velocity retardation due to incomplete thawing.

A shrinking core model of the melting or solidification of the PCM in the capsules was developed to document the internal heat transfer constraints within the capsules. The results of that study support the conclusion that slower wave velocities occur due to partial melting.
Sensitivity Analysis of Interfacial Momentum Closure Terms in Two Phase Flow and Boiling Simulations Using MCFD Solver
Authors: Liu Yang , Rollins Chad , Dinh Nam , Luo Hong
Published: October 2017

In this paper, a general workflow for the global Sensitivity Analysis (SA) has been proposed based on the coupling of VUQ toolkit DAKOTA and Multiphase Computational Fluid Dynamics (MCFD) solver boilEulerFoam. A surrogate model is first constructed based on sampling simulations from boilEulerFoam. This surrogate is based on Gaussian Processes Model (GPM) and is validated and proved to have good properties. The Morris Screening method is then applied based on the surrogate to those interfacial momentum closure terms for SA, including drag, lift, turbulent dispersion, wall lubrication, and virtual mass. Two different cases are considered, one is on low-pressure adiabatic flow, and the other is on high pressure boiling flow. Each case has its experimental background with data support. The radial void fraction distribution, gas velocity, relative velocity and liquid temperature (only for high pressure boiling case) are chosen as the Quantities of Interest (QoIs) which are of key interests for two-phase flow simulation and boiling crisis prediction. The interfacial force coefficient of each closure term is chosen as the input parameter. For the boiling case, the bubble diameter effect is also analyzed.

Three remarks are drawn from this work on SA. First, it demonstrates the feasibility of surrogate model in the VUQ work for models in MCFD solver. The computational cost can be significantly reduced by employing the surrogate model. Secondly, through the Morris Sensitivity measurements, the importance of interfacial forces on different QoIs and regions can be analyzed and ranked for the two cases. Such analysis is also helpful for further model parameter calibration. Last but not least, the limitation of current work and the desired future work are discussed.
Thermal Energy Transport Below the Diffraction Limit in Close-Packed Metal Nanoparticles
Authors: Yuksel Anil , Cullinan Michael , Murthy Jayathi
Published: October 2017

Fabrication of micro and nanoscale electronic components has become increasingly demanding due to device and interconnect scaling combined with advanced packaging and assembly for electronic, aerospace and medical applications. Recent advances in additive manufacturing have made it possible to fabricate microscale, 3D interconnect structures but heat transfer during the fabrication process is one of the most important phenomena influencing the reliable manufacturing of these interconnect structures. In this study, optical absorption and scattering by three-dimensional (3D) nanoparticle packings are investigated to gain insight into micro/nano heat transport within the nanoparticles. Because drying of colloidal solutions creates different configurations of nanoparticles, the plasmonic coupling in three different copper nanoparticle packing configurations were investigated: simple cubic (SC), face-centered cubic (FCC) and hexagonal close packing (HCP). Single-scatter albedo (ω) was analyzed as a function of nanoparticle size, packing density, and configuration to assess effect for thermo-optical properties and plasmonic coupling of the Cu nanoparticles within the nanoparticle packings. This analysis provides insight into plasmonically enhanced absorption in copper nanoparticle particles and its consequences for laser heating of nanoparticle assemblies.
Maximum Likelihood Method for Energy Balance Error Correction in Heat Exchanger Data
Authors: Park Young-Gil , Liu Liping , Jacobi Anthony M.
Published: October 2017

Heat exchanger performance data commonly contain redundant heat transfer rate measurements. Due to measurement uncertainties involved in the experiments, these redundant heat transfer rates have some discrepancies. While it is a common practice and adopted by engineering standards to use the arithmetic mean of heat transfer measurements, the resulting performance indicators of heat exchangers do not result in a minimum uncertainty possible. Also, this approach fails to resolve discrepancies in resulting transport performance parameters depending on the use of UA-LMTD method or effectiveness-NTU method. In this paper, heat exchanger performance data with two heat transfer measurements from hot and cold fluid streams are combined to produce a least uncertainty of the performance indicators. Individual measurements of mass flow rates and temperatures are corrected by most likely errors based on their respective uncertainties. The validity of this method has been demonstrated by Monte-Carlo simulations. Using air conditioning heat exchanger performance data under dry and wet surface conditions, it is demonstrated that the proposed method leads to a minimum uncertainty of the calculated variables.
A Numerical and Experimental Investigation on Impinging Round Jets in Channel Partially Filled With Porous Media
Authors: Buonomo Bernardo , Cirillo Luca , Manca Oronzio , Nardini Sergio
Published: October 2017

In this paper a numerical and experimental investigation on impinging jets with metal foam is carried out. The channel is partially filled with porous media. The physical model and geometry has been made considering that the lower impinging surface is heated at uniform heat flux, qw, and the upper surface is adiabatic. The flow is 2D, unsteady, laminar, and incompressible. The distance between the upper confining surface and the lower heated surface is H (40 mm). Fully developed fluid dynamic and thermal flow is assumed at the outlet sections and the fluid is air. The porous material is considered as homogeneous and isotropic. All the thermophysical properties of the fluid and the solid matrix of the porous medium are assumed constant except for the variation in density with the temperature giving rise to the buoyancy forces. Metal foam of 10 PPI is considered. It was investigated many configuration taking into account the ratio s/H and Dj/H. The values of ratio s/H ranging from 0 to 1 while values of the ratio Dj/H raging from 0.3–1.2. Results in terms of wall temperature profiles, local and average Nusselt numbers are presented for different Reynolds values. For the considered parameters, it is obtained that Nusselt number has a weak dependence of Dj/H, in fact, for the ratio equal to 0.3, it is noted that Nu is higher than the ratio equal to 0.6.
Cooling Performance Comparison of a Low Aspect Ratio Incremental Impingement Pin-Fin Channel Configurations
Authors: Singh Susheel , Acharya Sumanta , Ames Forrest
Published: October 2017

The effective use of coolant in maintaining gas turbine components below failure limits is becoming increasingly necessary in view of increasing combustor exit temperatures. Incorporating coolant impingement in a pin-finned channel provides an avenue for increased heat transfer. Two types of cooling configuration are modeled and compared: case 1: with the jet impinging in a cut out region behind a pin-fin (thus sheltering the jet from crossflow effects), and case 2: with the jet impinging further downstream along the next row of pin-fin and downstream of the wake region of the upstream pin-fin. In the current work, a Large Eddy Simulation (LES) study is conducted for a Reynolds number of 7500. All other geometrical and flow parameters are kept similar in both the configurations to enable a direct comparison. Since the stagnation point Nusselt number is not affected by the cross-flow in the sheltered configuration, there is enhanced cooling as compared to the configuration in which the jet impinges further downstream and is not protected from the crossflow. In this paper, the flow field, the jet-crossflow interactions and the heat transfer behavior are discussed for both the configurations.
Effect of Perforation Size to Perforation Spacing on Heat Transfer in Laterally Perforated-Finned Heat Sinks
Authors: Shaeri Mohammad Reza , Bonner Richard
Published: October 2017

Thermo-fluid characteristics of laterally perforated-finned heat sinks (LA-PFHSs) are investigated through experiments in laminar forced convection flows, in order to understand the key parameters affecting thermo-fluid transport phenomena and, in turn, parameters that play important roles to correlate heat transfer coefficients of LA-PFHSs. For this purpose, the Nusselt numbers of the LA-PFHSs are calculated using the well-accepted technique in the literature that was proposed to model Nusselt numbers of the slotted-finned heat sinks. Square cross sectional perforations at three different sizes are distributed along the length of the LA-PFHSs in inline configurations. Each perforation size is tested under five different porosities. The accuracy of the experiments are validated by comparing the pressure drops and Nusselt numbers of the imperforated heat sink against the correlated values obtained from the well-accepted correlations in the literature. Results indicate that the flow interactions over the perforations with each other are dominant mechanisms that affect transport phenomena in LA-PFHSs. The flow interactions with each other are proportional to the ratio of the perforation size to the solid distance between two-adjacent perforations. Therefore, this dimensionless geometrical parameter is found as the key parameter affecting thermo-fluid transport phenomena and, in turn, correlations to predict heat transfer coefficients of LA-PFHSs. At the end, suggestions are provided to develop physics-based correlations to predict heat transfer coefficients of LA-PFHSs through future research.
Performance Analysis of High Temperature Sensible Heat Thermal Energy Storage Systems for Concentrated Solar Thermal Power Plants
Authors: Mostafavi Tehrani S. Saeed , Shoraka Yashar , Taylor Robert A. , Menictas Chris
Published: October 2017

Due to their relatively high capital and environmental cost of two-tank molten salt thermal storage systems, a significant amount of research has gone into looking for sensible and latent thermal energy storage alternatives suitable for concentrated solar thermal (CST) plants. Despite a large number of developments in the last decade, comparative studies among promising options have been lacking. In particular, only a few comparative studies are available in which thermal energy storage (TES) systems are integrated as an active subcomponent of CST plant. Therefore, this study compares selected sensible heat thermal energy storage systems based on their integrated performance with other CST components (e.g. a tower -based CST plant with a Rankine cycle) over a year of operation.

In the present study, annual performances of single-medium thermocline (SMT), double-medium thermocline (DMT), and shell-and-tube (ST) system were compared with that of a conventional two-tank molten salt storage system. Concrete with porosity of 0.2 (concrete occupies 80% of the system) was selected as a low cost filler material in the DMT and ST systems. The systems were sized for 15 hours of storage capacity and integrated into a validated 19.9 MWe Gemasolar power plant model with solar multiple of 2.5. Before performing annual integrated simulations, an optimum design of each storage system was selected based on a performance analysis of the storage system over a constant 15 hours discharge. A CST plant with a two-tank molten salt system enables the highest amount of electricity generation in a year followed by the SMT and DMT systems, which resulted in 7% and 9% less electricity generation, respectively. For the CST plant with ST system, 20% less electricity was generated over a year. Overall, this study provides a methodology for the comparison of the TES alternatives, and it gives insight the most promising alternative for replacing two-tank molten salt systems.
Inversion for Fire Heat Release Rate Using Transient Heat Flux Data
Authors: Kurzawski Andrew , Ezekoye Ofodike A.
Published: October 2017

The heat-release rate (HRR) of a burning item is key to understanding the thermal effects of a fire on its surroundings. It is, perhaps, the most important variable used to characterize a burning fuel packet and is defined as the rate of energy released by the fire. HRR is typically determined using a gas measurement calorimetry method. In this study, an inversion algorithm is presented for conducting calorimeter on fires with unknown HRRs located in a compartment. The algorithm compares predictions of a forward model with observed heat fluxes from synthetically generated data sets to determine the HRR that minimizes a cost function. The effects of tuning a weighting parameter in the cost function and the issues associated with two different forward models of a compartment fire are examined.
Numerical Investigation of Buoyancy Effect on Mixed Convection Heat Transfer Deterioration of Supercritical Pressure Carbon Dioxide
Authors: Tang Guoli , Li Zhouhang , Wu Yuxin , Liu Qing , Lyu Junfu , Gu Junping
Published: October 2017

For supercritical pressure fluid upward pipe flow, turbulent mixed convection heat transfer deterioration, which is generally considered to be caused by buoyancy, is often put a deep concern for safety issues. The deterioration is typically characterized by a localized wall temperature peak. Sometimes, there will be another moderate temperature peak after the first one. However, due to the lack of reliable measure method, the understanding of the flow structure for these two localized temperature peaks were still limited. In order to investigate the detailed mechanism for these two peaks and further understand the effect of buoyancy, a numerical study of supercritical pressure carbon dioxide pipe flow mixed convection heat transfer deterioration was conducted in this paper. The SST k-omega model was selected as turbulence model. A variable turbulent Prandtl number model was adopted in the study to improve simulation accuracy. The variation of flow field and turbulence behavior were carefully analyzed. The results show that, the localized wall temperature rise is due to the suppressed turbulence in the near wall region. For the first localized temperature peak, the suppressed turbulence is due to the acceleration of near wall fluid. While for the second one, the restrained turbulence is due to the acceleration of core flow fluid.
Effect of Surface Roughness on the Behavior of Bubbles Growing and Departing From a Heated Surface
Authors: Dhillon Navdeep S.
Published: October 2017

The phenomenon of bubble growth on a heated surface is of fundamental importance in many scientific and engineering applications, including boiling heat transfer. Although the growth of a homogeneous bubble in a pool of hot liquid is well understood, bubbles growing on hot solid surfaces involve evaporation from a three-phase contact line and therefore exhibit several peculiar features. One of these is the effect of surface texture and wetting properties on the size and timing of bubbles that form and depart from a uniformly heated surface. Here, we present pool boiling experimental results elucidating this important phenomenon. Using high-speed optical imaging, we perform a comparative study of the process of growth and departure of bubbles on plain and rough surfaces and explore the different factors that dictate this behavior. Using scaling analysis, we analyze the primary forces acting on a growing bubble and show that the effect of surface roughness on bubble behavior can be explained in terms of the dependence of these forces on the rate of bubble growth and in-turn on the rate of thin-film evaporation from the three-phase contact line of the bubble.
Radiation Characteristics of a Particle Curtain in a Free-Falling Particle Solar Receiver
Authors: Kumar Apurv , Kim Jin-Soo , Lipiński Wojciech
Published: October 2017

Radiation absorption by a particle curtain formed in a solar free falling particle receiver is investigated using a Eulerian-Eulerian granular two-phase model to solve the two-dimensional mass and momentum equations (CFD). The radiative transfer equation is subsequently solved by the Monte-Carlo (MC) ray-tracing technique using the CFD results to quantify the radiation intensity through the particle curtain. The CFD and MC results provide reliable opacity predictions and are validated with the experimental results available in literature. The particle curtain was found to absorb the solar radiation efficiently for smaller particles at high flowrates due to higher particle volume fraction and increased radiation extinction. However, at low mass-flowrates the absorption efficiency decreases for small and large particles.
The Current Status of CANDU Steam Generators
Authors: Naraine Matthew , Riznic Jovica
Published: October 2017

This paper analyzes world steam generator (SG) operational experience (OPEX), research and development (R&D) for operational CANDU SGs. Emphasis is placed on design configuration, materials, and chemistry. SG OPEX from various databases is recounted to identify performance trends, active degradation mechanisms and common failure modes. A summary of CANDU and pressurized water reactor (PWR) SG OPEX including tube plugging statistics by material and degradation mechanism is provided. A discussion of ongoing SG-related research initiatives is also included. It was found that SGs with Monel-400 tubing and carbon steel tube support would perform well if properly maintained although Incoloy-800 tubing and stainless steel tube support is the current preferred design for CANDU, regarding Inconel-600 as an interim solution. All volatile treatment has also been adopted as the preferred SG chemistry for the CANDU fleet. Lessons learned from OPEX are highlighted and further international collaboration on the study of plant ageing, SG integrity, and nuclear safety is encouraged.
Numerical Study on Momentum Transfer Between Droplets and Carrier-Phase in Wave-Type Plate Separators
Authors: Yuzheng Li , Qianfeng Liu , Hanliang Bo
Published: October 2017

The steam flow is simulated by FLUENT. The Lagrange-Euler method is used to simulate the droplet-laden flow in wave-type separators. Two-way coupling method is used to study the influence of the momentum transfer between droplets and carrier-phase in wave-type plate separators. A group of the trajectories of droplets with different diameters are performed in wave-type plate separator flow field. The result shows that the momentum transfer has tiny impact on the behaviors of droplets in a low velocity flow. However, the momentum transfer affects the behaviors of droplets more significantly with rising flow velocity. The one-way coupling method overestimates the diffusion of droplets. In addition, the momentum transfer affects the total pressure loss more significantly with rising volume fraction. The conclusion verifies the importance of the momentum transfer in droplet-laden flows, which could be used to simulate the behavior of droplets moving in a separator.
Analysis and Research on Diagnosis Methods of AFA 3G Fuel Assembly Leakage
Authors: Xiaohui Wei
Published: October 2017

Based on the design and manufacture characteristics of AFA 3G high performance fuel assembly, this paper analyzes the various factors that lead to leakage of the fuel assembly, which is mainly escape of radioactive products caused by failure of the fuel cladding tubes. Aiming at the fuel assembly leakage, this paper comparatively analyzes three main diagnosis methods, including radioactive activity calculation of fission products, sipping test and ultrasonic detection technique. At the same time, the detection results are analyzed and verified for on-site detection of ultrasonic device, finally this paper raises improvement analysis of ultrasonic detection technique so that facilitating research and implementation of fuel assembly leakage detection better in the future.
Comparative Study of Basic Reactor Physics of the DFR Concept Using U-Pu and TRU Fuel Salts
Authors: Wang Xiang , Macian-Juan Rafael
Published: October 2017

The Dual Fluid Reactor (DFR) is a molten salt fast reactor developed by the IFK1 based on the Gen-IV Molten-Salt Reactor (MSR) and the Liquid-Metal Cooled Reactor (SFR, LFR) concepts. The analysis reported focuses on the comparison between previous neutronic calculations with the default fuel salt of U-Pu mixture and new ones with a transuranium (TRU) salt fuel option under steady state conditions. They include criticality, neutron spectrum, spatial flux distribution and temperature coefficient values. Fuel based on molten TRU salts has already been considered for the MSFR and other molten salt reactor designs. Therefore, the DFR for the first time has a comparable baseline with other molten salt reactors, so that its performance with TRU salt fuel can be assessed.
PSA Application in the Diverse Actuation System Design
Authors: Wenhui Zhan , Binbin Zhang
Published: October 2017

Diverse Actuation System (DAS) is designed as a diverse backup system for Protection and Safety Monitoring System (PMS) to perform the functions of reactor trip and engineered safety features actuation in AP1000 type nuclear power plants. However, not all of the PMS functions should be included in the DAS design. In this paper, the Probabilistic Safety Assessment (PSA) technique was used to identify the DAS functions by comparing the core damage frequency caused by initiating events in at-power internal event PSA. Furthermore, protection parameter signals of DAS to actuate mitigating systems are identified by accident progress analysis.
Data Processing Method for Effective Thermal Diffusivity Experiment of Pebble Bed in High Temperature Gas-Cooled Reactors
Authors: Wu Yongyong , Ren Cheng , Li Rui , Cheng Pengxin , Yang Xingtuan , Tu Jiyuan
Published: October 2017

The effective thermal diffusivity and conductivity of pebble bed in the High Temperature Gas-cooled Reactor (HTGR) are two vital parameters to determine the operating temperature and power in varisized reactors with the restriction of inherent safety. A high-temperature heat transfer test facility and its inverse method for processing experimental data are presented in this work. The effective thermal diffusivity of pebble bed will be measured at temperature up to 1600 °C in the under-construction facility with the full-scale in radius. The inverse method presents a global optimal relationship between thermal diffusivity and temperature through those thermocouple values in the pebble bed facility. Furthermore, the robustness and uncertainty analyses are also set forth here to illustrate the validity of the algorithm and the corresponding experiment.
Comparative Study of Thermal-Hydraulic Behavior of the DFR Using U-Pu and TRU Salt Fuels
Authors: Wang Xiang , Macian-Juan Rafael
Published: October 2017

The Dual Fluid Reactor is a molten salt fast reactor developed by the IFK1 based on the Gen-IV Molten-Salt Reactor (MSR) and the Liquid-Metal Cooled Reactor (SFR, LFR) concepts. Based on previous researches an analysis focusing on the simulation on different dimensions of the DFR system with transuranium (TRU) salt fuel option is performed. The zero-dimensional point-kinetics model coupled with the zero-dimensional heat-transfer model constructed by SIMULINK will be set up first. The radial power profile of the fuel salts inside of the fuel tube cell is described by a two-dimensional system which focuses on the single fuel unit cell of the DFR with the equivalent cylindrical model instead of the original hexagonal prismatic shape. The comparison between the results is then discussed.
Summary and Experience Feedback on a Comprehensive Emergency Drill in INET
Authors: Xie Feng , Lou Mengqi , Zhang Liguo , Tong Jiejuan , Qu Jingyuan , Xiang Xincheng
Published: October 2017

Nuclear emergency is the important component part of the defense in depth philosophy of nuclear safety, which is the last barrier to protect public in a nuclear accident. According to Chinese codes and standards which are Regulations on the Nuclear Accident in Nuclear Power Plant and Emergency Preparedness and Emergency Response of the Research Reactor (HAD002/06), the research reactor operation units should carry out a comprehensive emergency drill at least once every two years, in order to check the effect of the emergency training about the on-site emergency organization and verify the usefulness and feasibility of the emergency plan. Therefore, the Institute of Nuclear and New Energy Technology (INET), Tsinghua University, had drew up the comprehensive emergency plan, conducted the emergency practice in December 2015, and tested the emergency preparedness of multiple research nuclear installations including the 10MW high temperature gas-cooled reactor (HTR-10), 5MW test heating reactor, shielding-experimental reactor, etc. The purpose, accident scenarios, process, and key content of the emergency drill were descripted in details, the design of the guiding worksheets which were adopted in the emergency drill of INET for the first time were distinctly introduced, and the effect of these guiding worksheets was explicitly discussed. The whole process of the drill in INET in 2015 was reviewed and summarized, the experience feedback of which can supply useful reference information and recommendations for the development of the emergency drill of research reactors.
Cycle Calculations of a Small-Scale Heat Removal System With Supercritical CO2 As Working Fluid
Authors: Strätz Marcel , Starflinger Jörg , Mertz Rainer , Seewald Michael , Schuster Sebastian , Brillert Dieter
Published: October 2017

In case of an accident in a nuclear power plant with combined initiating events, (loss of ultimate heat sink and station blackout) additional heat removal system could transfer the decay heat from the core to and diverse ultimate heat sink. On additional heat removal system, which is based upon a Brayton cycle with supercritical CO2 as working fluid, is currently investigated within an EU-funded project, sCO2-HeRo (Supercritical carbon dioxide heat removal system). It shall serve as a self-launching, self-propelling and self-sustaining decay heat removal system to be used in severe accident scenarios. Since a Brayton cycle produces more electric power that it consumes, the excess electric power can be used inside the power plant, e.g. recharging batteries. A small-scale demonstrator will be attached to the PWR glass model at Gesellschaft für Simulatorforschung GfS, Essen, Germany.

In order to design and build this small-scale model, cycle calculations are performed to determine the design parameters from which a layout can be derived.
Refined Algorithm for Solving High-Order Harmonics of Multi Group Neutron Diffusion Equation
Authors: Zhou Gaoxin , Gang Zhi
Published: October 2017

In recent years, high order harmonic (or eigenvector) of neutron diffusion equation has been widely used in on-line monitoring system of reactor power. There are two kinds of calculation method to solve the equation: corrected power iteration method and Krylov subspace methods. Fu Li used the corrected power iteration method. When solving for the ith harmonic, it tries to eliminate the influence of the front harmonics using the orthogonality of the harmonic function. But its convergence speed depends on the occupation ratio. When the dominant ratios equal to 1 or close to 1, convergence speed of fixed source iteration method is slow or convergence can’t be achieved. Another method is the Krylov subspace method, the main idea of this method is to project the eigenvalue and eigenvector of large-scale matrix to a small one. Then we can solve the small matrix eigenvalue and eigenvector to get the large ones. In recent years, the restart Arnoldi method emerged as a development of Krylov subspace method. The method uses continuous reboot Arnoldi decomposition, limiting expanding subspace, and the orthogonality of the subspace is guaranteed using orthogonalization method.

This paper studied the refined algorithms, a method based on the Krylov subspace method of solving eigenvalue problem for large sparse matrix of neutron diffusion equation. Two improvements have been made for a restarted Arnoldi method. One is that using an ingenious linear combination of the refined Ritz vector forms an initial vector and then generates a new Krylov subspace. Another is that retaining the refined Ritz vector in the new subspace, called, augmented Krylov subspace. This way retains useful information and makes the resulting algorithm converge faster. Several numerical examples are the new algorithm with the implicitly restart Arnoldi algorithm (IRA) and the implicitly restarted refined Arnoldi algorithm (IRRA). Numerical results confirm efficiency of the new algorithm.