bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of Sweating/Evaporation Boosted Convective Heat Transfer Under Laminar Flow Condition
Authors: Saha Sudipta , Mahamud Rajib , Khan Jamil , Farouk Tanvir
Published: October 2017

Phase change driven heat transfer has been the topic of interest for a significantly long time. However, in recent years on demand sweating boosted evaporation which requires substantially less amount of the liquid medium has drawn attention as a possible way of increasing/supplementing heat transfer under convective conditions where the convective heat transfer coefficient has already reached its maximum value as well as where dry cooling is a desired objective. In this study, a numerical study is conducted to obtain insight into the ‘hybrid’ system where evaporation and convection both contribute to the heat transfer effect. The system modeled consists of evaporation of thin liquid (water) film under a laminar flow condition. The mathematical model employed consists of coupled conservation equations of mass, species, momentum and energy for the convection-evaporation domain (gaseous), with only mass and energy conservation being resolved in the liquid film domain. The evaporative mass flux is obtained from a modified Hertz-Knudsen relation which is a function of liquid-vapor interface temperature and pressure. A two-dimensional rectangular domain with a pre-prescribed thin liquid water film representative of an experiment is simulated with the developed model. The thin rectangular liquid film is heated by uniform heat flux and is placed in the convection-evaporation domain with an unheated starting length. A moving boundary mesh is applied via the“Arbitrary Lagrangian-Eulerian” technique to resolve the receding liquid interface resulting from evaporation. The prescribed relative displacement of the moving interface is calculated from the net mass flux due to evaporation and is governed by the principle of mass conservation. Simulations were conducted over a range of Reynolds number, heat flux conditions and liquid film thickness. The numerical predictions indicate that under convective-evaporative conditions the overall heat transfer coefficient increases significantly (∼factor of a five) in comparison to the purely forced convection scenario. An increase in the heat transfer coefficient is observed with Reynolds number and vice versa for film thickness. A critical Reynolds number is identified beyond which the heat transfer coefficient does not continue to increase significantly rather tends to plateau out.
Thermal Conductivity Testing Apparatus for 3D Printed Materials
Authors: Flaata Tiffaney , Michna Gregory J. , Letcher Todd
Published: October 2017

Additive manufacturing, the layer-by-layer creation of parts, was initially used for rapid prototyping of new designs. Recently, due to the decrease in the cost and increase in the resolution and strength of additively manufactured parts, additive manufacturing is increasingly being used for production of parts for end-use applications. Fused Deposition Modeling (FDM), a type of 3d printing, is a process of additive manufacturing in which a molten thermoplastic material is extruded to create the desired geometry. Many potential heat transfer applications of 3d printed parts, including the development of additively manufactured heat exchangers, exist. In addition, the availability of metal/polymer composite filaments, first used for applications such as tooling for injection molding applications and to improve wear resistance, could lead to increased performance 3d printed heat exchangers because of the higher thermal conductivity of the material. However, the exploitation of 3d printing for heat transfer applications is hindered by a lack of reliable thermal conductivity data for as-printed materials, which typically include significant void fractions. In this experimental study, an apparatus to measure the effective thermal conductivity of 3d printed composite materials was designed and fabricated. Its ability to accurately measure the thermal conductivity of polymers was validated using a sample of acrylic, whose conductivity is well understood. Finally, the thermal conductivities of various 3d printed polymer, metal/polymer composite, and carbon/polymer composite filaments were measured and are reported in this paper. The materials used are acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), stainless steel/PLA, Brass/PLA, and Bronze/PLA.
Investigation of Operational Effects on Slab Heating Characteristics in a Pusher-Type Reheat Furnace With Continuous Slab Motion
Authors: Liu Xiang , Tang Guangwu , Silaen Armin , Cox Jeffrey , Johnson Kurt , Zhou Chenn
Published: October 2017

Reheat furnace is an important component in hot milling process consuming large amount of fuel and energy. In order to investigate the operational effects on slab temperature distribution, a three-dimensional computational fluid dynamics (CFD) model was developed to simulate the flow characteristics, combustion process, and multi-scale heat transfer inside a reheating furnace with continuous slab motion. ANSYS Fluent®, which is a mature commercial package, was used to conduct numerical simulation. The operation process was modeled with specific slab line-ups and fuel input conditions. The slab motion was modeled with dynamic mesh based on a transient heating process. The model was validated with measurement data at the ArcelorMittal hot rolling mill. The model aims to predict the temperature field in the furnace and the temperature evolution of the slab as it travels through the furnace.
Vapor Bubble Interaction With a Superheated Wall
Authors: Akhtar M. Wasy
Published: October 2017

Sliding bubbles are known to augment heat transfer rates on the surface on which they slide. The pre-cursor problem — the bubble approaching an inclined superheated wall provides the initial flow and thermal field for the sliding bubble problem. An FC-87 vapor bubble rising in a thermally stratified flow field is simulated along with the bubble wall interaction effects. The simulation is conducted on a dynamic octree grid for improved accuracy and efficiency. The evolution of the bubble shape and the wake behind the rising bubble is captured in a three-dimensional model, which takes into account bubble growth due to superheat at the liquid-vapor interface and the effect of interface heat flux on the local saturation temperature. After the first bubble-wall interaction, a microlayer tens of microns thick forms between the bubble and the wall; a thermal wake develops behind the bubble as it begins to slide against the wall.

The predicted shapes, Re and Weber numbers and microlayer thicknesses show excellent agreement in comparison to experimental data from other researchers. Evolution of the flow and temperature fields were examined with the aid of contours of vapor volume fraction and iso-lines of mixture temperature superimposed on three-dimensional shapes of the bubble. Overall bubble dynamics and microlayer dynamics, including microlayer thickness and microlayer heat flux, are presented as functions of time. Using the wall, microlayer and wake heat transfer rates, an enhancement of the total wall heat flux was found to be on the order of 6 times the background heat flux.

This work describes the bubble evolution through the first rebounding in detail, but the dynamic octree adaption algorithm lends itself to study of the long-term dynamics well into the sliding regime. The technique can also be used to investigate other multiphase flow phenomena — especially bubble coalescence and breakup.
Numerical and Experimental Analysis on High Power Density Multi-Fuel Rotary Engine Heat Redistribution Optimization Design
Authors: Zeng Wenwei , Okun Shawn
Published: October 2017

A revolutionary cooling system is designed for a multi-fuel rotary engine (200 cc, 40 hp). The patented cooling system includes a water cooled array of engine housings, an innovative rotor and hydrodynamic bearings set cooled with a secondary oil cooling system. The oil conduits, however, are incorporated into water jackets, therefore the heat is further transferred to the water flow. Numerous fins and ribs are utilized as deflectors in water jackets thus controlling water flow to carry heat from the “hot” side of the engine housing to the “cold” side, which minimize temperature differential over the housing as well as reducing peak temperature. Numerical simulation indicated hot spots and uneven temperature distribution issues were controlled in the water jackets. Testing the optimized water jackets as part of the cooling system was also shown in successful in controlling temperature, hot spots and cavitation on the rotary engine with multi-fuels testing, such as kerosene, JP-5, JP-8, alcohol, gasoline, and E85. The potential of applying current water cooling system in other rotary engines is feasible.
Enhanced Coherent Thermal Emission From SiO2 on a Porous Silicon Photonic Crystal
Authors: Juneau-Fecteau Alexandre , Belarouci Ali , Fréchette Luc G.
Published: October 2017

We show that coherent thermal emission from an amorphous SiO2 thin film can be significantly enhanced by placing it on top of a photonic crystal (PC). To demonstrate this principle, we simulated the reflectance and transmittance of a 1 micron thick layer of SiO2 on a 20 layers PC using the scattering matrix method and finite difference numerical computations. Emissivity, calculated using Kirchhoff’s law, reaches unity at a peak wavelength around 10 microns due to overlapping of the PC’s forbidden band with bulk phonon-polariton modes in SiO2. This region of the electromagnetic spectrum is of particular interest for many technological applications as it corresponds roughly to maximum thermal emission from a blackbody at room temperature. In order to validate these theoretical predictions, a PSi multilayer was fabricated by electrochemical dissolution of p-type Si in HF with current density modulated as a function of time to produce alternating layers of two different porosities with different refractive indices. A 1 micron thick layer of SiO2 was then deposited on top of the resulting PC by plasma enhanced chemical vapor deposition (PECVD). Reflectance of the PC was measured at normal incidence using a Fourier Transform Infrared Spectrometer (FTIR) before and after SiO2 deposition and matches the simulations.
Optimal Position of Rectangular Vortex Generator for Heat Transfer Enhancement in a Flat-Plate Channel
Authors: Khan Tariq Amin , Li Wei , Zhang Zhengjiang , Du Jincai , Khan Sadiq Amin , Liu Fu
Published: October 2017

Heat transfer is a naturally occurring phenomenon which can be greatly enhanced by introducing longitudinal vortex generators (VGs). As the longitudinal vortices can potentially enhance heat transfer with small pressure loss penalty, VGs are widely used to enhance the heat transfer of flat-plate type heat exchangers. However, there are few researches which deal with its thermal optimization. Three dimensional numerical simulations are performed to study the effect of angle of attack and attach angle (angle between VG and wall) of vortex generator on the fluid flow and heat transfer characteristics of a flat-plate channel. The flow is assumed as steady state, incompressible and laminar within the range of studied Reynolds numbers (Re = 380, 760, 1140). In the present work, the average and local Nusselt number and pressure drop are investigated for Rectangular vortex generator (RVG) with varying angle of attack and attach angle. The numerical results indicate that the heat transfer and pressure drop increases with increasing the angle of attack to a certain range and then decreases with increasing angle of attack. Moreover, the attach angle also plays an importance role; a 90° attach angle is not necessary for enhancing the heat transfer. Usually, heat transfer enhancement is achieved at the expense of pressure drop penalty. To find the optimal position of vortex generator to obtain maximum heat transfer and minimum pressure drop, the data obtained from numerical simulations are used to train a BRANN (Bayesian-regularized artificial neural network). This in turn is used to drive multi-objective genetic algorithm (MOGA) to find the optimal parameters of VGs in the form of Pareto front. The optimal values of these parameters are finally presented.
Fabrication and Thermal Characterization of Novel Copper-CNT Micropillars for Electronics Cooling Applications
Authors: Ghanbari Siavash , Darabi Jeff
Published: October 2017

This paper presents an experimental investigation to study the thermal and material characterization of an array of composite copper-carbon nanotubes (CNT) micropillars for applications in passive two-phase cooling systems. These novel micropillar structures have a larger spacing at the base of the micropillars to provide a higher liquid permeability and mushroom-like structures on the top surface of the micropillars with a smaller spacing to provide a greater capillary pressure. First, composite copper-CNT micropillars are fabricated by an electrodeposition method on a patterned copper template. Then, cauliflower-like nanostructures are grown on the top surface of the micropillars using chronoamperometry technique to improve the capillary pressure and thermal performance of the micropillars. Finally, a series of tests are conducted to quantify the thermal performance of the fabricated micropillars. The results indicate that the performance of mushroom-like composite copper-CNT micropillars is significantly higher than those of copper micropillar arrays.
CFD Simulation of Pool Boiling for Liquid Nitrogen
Authors: Zhou Peng , Xu Yongqi , Wang Xiuling
Published: October 2017

Computational Fluid Dynamics model is developed to simulate pool boiling for liquid nitrogen. Instead of using the user defined function (UDF), the evaporation-condensation model is adopted to take care of the energy term when phase change happens. Test cases with different excess temperature are simulated to study the important heat transfer features in different boiling regimes — free convection boiling, nucleate boiling, transition boiling and film boiling. The heat flux for each case is calculated. Simulation results are compared with the experimental and numerical data in the literature, good agreements are observed. By using the evaporation-condensation model, the pool boiling procedure is successfully simulated, and the complex physical process such as the pool vaporization can be clearly analyzed. At last, some comments and improvements are discussed to increase the accuracy of the simulation.
Unsteady Flow Modelling in Plate-Fin Heat Exchanger Channels
Authors: Greiciunas Evaldas , Borman Duncan , Summers Jonathan
Published: October 2017

A methodology using Computational Fluid Dynamics (CFD) was developed to predict the flow and heat transfer performance of a single two dimensional sinusoidal channel of a Heat Exchanger (HE) at a Reynolds number (Re) range of 5 ≤ Re ≤ 500. The impact of different modelling assumptions was thoroughly evaluated which has not has been done in detail before. Two computational domains were used: a single period sinusoidal channel for fully periodic flow predictions and finite length channel consisting of 6 sinusoidal channel periods. Mesh and time independence was achieved for both domains whilst results with periodic domain were compared to numerical results in the literature. Laminar, k-ε and k-ω SST predictions were assessed throughout the Reynolds range with unsteady flow onset detected at Re ≈ 200 using laminar and k-ω SST models. The impact of different accuracy numerical discretisation schemes is assessed throughout the Re range and it was found that second order accuracy schemes should be used to fully capture the unsteady flow. Comparison between open-source CFD package OpenFOAM and Ansys was Fluent was performed and agreement was ‘ found.
Numerical and Experimental Investigations on Longitudinal Vortex Generator for Heat Transfer Enhancement in Rectangular Channel
Authors: Li Zheng , Ke Zhaoqing , Li Kuojiang , Xu Xianchen , Chen Yangyang , Zhou Keyu , Chen Hsiu-Hung , Huang Guoliang , Chen Chung-lung , Chen Chien-Hua
Published: October 2017

In this article, longitudinal vortex generator (LVG) for heat transfer enhancement in rectangular channel is investigated numerically and experimentally. Two symmetrical delta shaped plates are placed vertically at the bottom of a rectangular channel and a pair of longitudinal vortices are generated and transferred downstream. These vortices were clockwise and counterclockwise, respectively. Correspondingly, the flow has the tendency to shoot to the surface opposite to the one with the LVG, then it separates into two steams and runs back to the LVG surface. Local heat transfer enhancement in the rectangular channel varies due to this fountain effect. Size effects were discussed for two types of LVG. With the same height, the wider LVG has better thermal performance within the rectangular geometry limit. One specific LVG was fabricated and tested experimentally and results show significant heat transfer enhancement. It indicated that the LVG can enhance the heat transfer significantly and the numerical results are reliable.
Heat Transfer in the Wake of a Highly Confined Bubble in Horizontal Channel Flow
Authors: Willard John R. , Hollingsworth D. Keith
Published: October 2017

A numerical investigation of a single highly confined bubble moving through a millimeter-scale channel in the absence of phase change is presented. The simulation includes thermal boundary conditions designed to match those of completed experiments. The channel is horizontal with a uniform-heat-generation upper wall and an adiabatic lower boundary condition. The use of a Lagrangian framework allows for the simulation of a channel of arbitrary length using a limited computational domain. The liquid phase is a low-Reynolds-number unsteady laminar flow, and the phase interactions are modeled using the Volume-of-Fluid method with full geometric reconstruction of the liquid/gas interface. Results are presented for two bubble sizes, two liquid flow rates, and two Prandtl numbers. The paper focuses on heat transfer in the rearward wake of the bubble. Nusselt numbers for the higher Prandtl number case are shown to follow a power law relationship with distance behind the bubble. Important dynamical structures include a pair of vortical structures at the rear of the bubble associated with cold fluid being brought near the wall and fluid jets oriented in the transverse direction to either side of the bubble.
Phase Change Materials (PCMs) in a Parallel Squared Honeycomb System for Electronic Cooling
Authors: Buonomo Bernardo , Ercole Davide , Manca Oronzio , Fedele Laura , Mancin Simone
Published: October 2017

The present work aims to investigate a honeycomb module with PCM for electronic passive cooling. The system is a honeycomb squared solid matrix filled with Phase Change Material. The PCM is paraffin wax and the honeycomb material is aluminum. Transient regime numerical simulations are created with different configurations, for different pores per unit of length (PPU) and different thermal power. A numerical model with honeycomb structure is compared with a porous medium model. The behavior of the porous medium is modeled with the Darcy-Forchheimer assumption and local Thermal Non-Equilibrium (LTNE) hypothesis is employed to simulate the heat transfer between the fluid zone and the solid zone. The results are presented in term of melting time, melt fraction evolution, temperature fields and stored energy for the charging phase.
Surface Geometry Optimization for Convection Flow Over Super Hydrophobic Surfaces
Authors: Bhusal Sadhana , Phan Long , Lin Cheng-Xian
Published: October 2017

Drag reduction in fluid flows using the concept of a super hydrophobic surface has recently gained attentions from several researchers. The hydrophobic surfaces developed are inspired by the non-wetting properties of a lotus leaf. They find several applications in areas like, self-cleaning surfaces, mixing in laminar flows and others.

In this paper, computational studies were done for isothermal pure water along with the focus in the surface optimization. Different possible geometries are investigated with the use of commercial computational fluid dynamics code. Parametric study on the geometrical variations of the surface is the main discussion of the current paper, as well as their effects on the wetting. Some of the geometrical variations are the square, rectangular, and isosceles triangular groove surfaces. The drag reduction was found to increase by increasing the roughness spacing and decreasing the roughness height irrespective of the type of the surface geometry.
Improving Cooling Efficiency by Using Mixed Tiles to Control Airflow Uniformity of Perforated Tiles in a Data Center Model
Authors: Phan Long , Bhusal Sadhana , Lin Cheng-Xian
Published: October 2017

Data centers in recent years have grown so fast so that their energy consumptions become a big issue in the industrial sector. One of the strategies to make better use of energy in data centers is to improve the efficiency in cooling. As the load density in data centers increases dramatically over the years, the number of computer room air handlers (CRAHs) are also increased to accommodate the high cooling demands. However, the number of CRAH units and their layouts really affect the air flow through the perforated tiles. Non-uniform airflow distributions in the perorated tiles in the cold aisles cause inefficient cooling of all the servers mounted in racks in data centers. Application of necessary strategies to minimize airflow non-uniformity is therefore very important because of its direct impact on the power density capacity. In this paper, a simulation study to examine how computer room air handler (CRAH) positions, the number of operating units, and tile types affect the airflow uniformity in selected data center models. Also, the placement of mixed tiles in cold aisles to regulate the airflow through the perforated tiles to accommodate greater heat loads from server racks is evaluated.
Analytical Solutions of Enhanced Gray Boltzmann Transport Equation on Transient Thermal Grating and Time-Domain Thermoreflectance Experiments
Authors: Wang Dadong , Qu Zhengxian , Ma Yanbao
Published: October 2017

As reported by many studies, Fourier’s law breaks down in micro/nanoscale due to the nondiffusive heat transport. To account for the nondiffusive heat transport, high-fidelity nondiffusive models with good efficiency for the experimental data analysis in nanothermometry are necessary but unfortunately missing. In this paper, based on a validated enhance Gray Boltzmann transport equation, we offer the analytical solutions for two important nanothermometry techniques, namely the transient thermal gratings (TTG) and time-domain thermoreflectance (TDTR) experiments. The analytical solutions obtained by inverse Fourier transform are compared to the experimental signals in both TTG and TDTR cases. The excellent agreements between the analytical solutions and the experiments demonstrate the applicability of the EG-BTE in experimental data analysis as an efficient replacement of Fourier’s law.
Predicting Particle Size Distribution in Nanofluid Synthesis
Authors: Ma Binjian , Banerjee Debjyoti
Published: October 2017

Wet chemistry approaches have been widely used to synthesize nanoparticle suspensions with different size and shape. Controlling particle size is crucial for tailoring the properties of the nanofluid. In this study, we simulated the particle size growth during a thermal-chemical nanofluid synthesis routine. The simulation was based on the population balance model for aggregation kinetics, which is coupled with thermal decomposition, nucleation and crystal growth kinetics. The simulation result revealed a typical burst nucleation mechanism towards self-assembly of supersaturated monomers in the nanoparticle formation process and the shift from monodispersed particles to polydispersed particles by the particle-particle coagulation.
Zinc Composites With Enhanced Thermal Conductivity for Use in Fused Deposition Modeling Systems
Authors: Sonsalla Tyler J. , Weiss Leland , Moore Arden , Radadia Adarsh , Wood Debbie , Bailey Davis
Published: October 2017

Waste heat is a major energy loss in manufacturing facilities. Thermally conductive polymer composite heat exchangers could be utilized in the ultralow temperature range (below 200° C) for waste heat recovery. Fused deposition modeling (FDM), also known as three-dimensional (3-D) printing, has become an increasingly popular technology and presents one approach to fabrication of these exchangers. The primary challenge to the use of FDM is the low-conductivity of the materials themselves. This paper presents a study of a new polymer-Zn composite designed for enhanced thermal conductivity for usage in FDM systems. Thermal properties were assessed in addition to basic printability. Filler volume percentages were varied to study the effects on material properties. Scanning electron microscope (SEM) images were taken of the 3-D printed test pieces to determine filler orientation and filler distribution. Lastly, experimentally obtained thermal conductivity values were compared to the theoretical thermal conductivity values predicted from the Lewis-Nielsen model.
Controlling Effect of Oxygen Concentration on Fire Behavior in Low Air Pressure Cargo Compartment
Authors: Wang Wei , Zhang Hui , Yang Rui , Ma Qiuju , Liu Xiaodong , Li Cong , Tao Zhenxiang
Published: October 2017

Cargo compartment fire has become the major security threat for cruising aircraft, the depressurization measurement could effectively suppress the cargo compartment fire through the reduction of the air pressure and oxygen concentration. The objective of this work is to study fire behavior characteristics in half confined chamber and high altitude laboratory at identical low atmospheric pressure, and explore the controlling effects of air exhaust condition, oxygen concentration. N-heptane pool fire experiments were conducted separately in Langfang low pressure chamber (altitude 50m) and Kangding airport laboratory (altitude 4290m) at 60 kPa air pressure, both assembled ISO-9705, but their gas supplying condition is different. Mass burning rate, gas composition, flame temperature, and radiant heat flux had been measured as the principal characteristic parameters for analysis. This paper reveals the variation characteristics of the fire behavior under different oxygen concentration but identical low atmospheric pressure. The gas composition of the chamber is controlled by the liquid fire and air intake quantity, the oxygen concentration of the chamber decreases with decreasing gas intake quantity. The mass burning rate increases and the mass burning time decreases with the increase of the oxygen concentration. The higher air intake quantity or the higher oxygen concentration could increase cargo compartment fire radiation intensity, and exacerbate the fire further propagation. However, under the low oxygen concentration condition, the liquid fire still have a higher flame temperature above a certain height. The depressurization measurement could increase the flame height and flame temperature may be caused the cabin fire-resistant liners layer is easier to burn through. The more reasonable adjustment of the cargo compartment air exhaust quantity and air pressure is very meaningful for the comprehensive fire suppression of cruising commercial airplanes.
Multiscale Simulation of Surface Nanostructure Effect on Bubble Nucleation
Authors: Mao Yijin , Zhang Bo , Chen Chung-Lung , Zhang Yuwen
Published: October 2017

Effects of nanostructured defects of copper solid surface on the bubble growth in liquid argon have been investigated through a hybrid atomistic-continuum method. The same solid surfaces with five different nanostructures, namely, wedge defect, deep rectangular defect (R-I), shallow rectangular defect (R-II), small rectangular defect (R-III) and no defect, have been modeled at molecular level. The liquid argon is placed on top of the hot solid copper with superheat of 30 K after equilibration is achieved with CFD-MD coupled simulation. Phase change of argon on five nanostructures has been observed and analyzed accordingly. The results showed that the solid surface with wedge defect tends to induce a nano-bubble relatively more easily than the others, and the larger the size of the defect is the easier the bubble generate.
Dense Wire Mesh as a High-Efficiency Solar Volumetric Absorber
Authors: Livshits Maya , Avivi Lior , Kribus Abraham
Published: October 2017

Heating a gas to over 1,000°C with concentrated sunlight can enable advanced high-performance applications such as solar-driven combined cycles and solar thermo-chemical processes. Solar receivers using volumetric porous absorbers are intended to produce the ‘volumetric effect’ leading to reduced heat loss and high absorber efficiency. However, experiments on volumetric absorbers have not shown this effect, and the absorbers’ efficiency is usually in the range of 70–80% rather than the desirable range of over 90%. Several porous structure geometries, including the well-known ceramic honeycomb and ceramic foam, were investigated with a numerical model. The results show that even optimal configurations still fall short of the desired range of absorber efficiency. A new candidate structure, a dense wire mesh, was investigated and compared to the conventional absorbers. The volumetric convection coefficient was also measured experimentally to provide validation of the single report found in the literature for this structure. An attractive solution with high efficiency of 90% was found for a dense wire mesh with pore diameter of 1 mm and porosity of 0.83. This geometry seems then a promising candidate for future volumetric absorbers.
Application of Laser-Induced Fluorescence, Particle Velocimetry and Infrared Thermography to Heated Falling-Film Flows
Authors: Charogiannis Alexandros , Markides Christos N.
Published: October 2017

We investigate the unsteady heat transfer in harmonically excited liquid-film flows falling under the action of gravity over an electrically-heated inclined glass-substrate, by simultaneous application of planar laser-induced fluorescence (PLIF), particle image and particle tracking velocimetry (PIV/PTV), and infrared thermography (IR). These non-intrusive optical techniques allow us to recover detailed information on the film-height ( PLIF), the velocity field underneath the wavy interface (PIV/PTV), and the free-surface (gas-liquid interface) temperature (IR), with high spatial and temporal resolution. Based on these data and knowledge of the applied heat-flux and substrate temperature at the measurement location, the local and instantaneous heat-transfer coefficient (HTC) is also evaluated. Preliminary results from select flow-regions suggest significant deviations compared to expectations from equivalent steady flows.
Heat Transfer in Additive Manufacturing of Glass
Authors: Luo Junjie , Hostetler John M. , Bristow Douglas A. , Landers Robert G. , Kinzel Edward C. , Goldstein Jonathan T.
Published: October 2017

The temperature in the molten region is a critical parameter for Additive Manufacturing (AM) of transparent glass using a laser heated filament-fed processing. This paper presents a study of the heat transfer in single track printing of borosilicate glass using the filament-fed process. The incandescent radiation emitted from the melt pool is monitored using a spectrometer. The spectral data indicates the breakdown of materials occurring inside of the glass, and reflects the occurrence of bubble formation due to reboil at high temperatures. A simple numerical model of the filament-fed process based on an energy balance within the melt pool is used to estimate the temperature. By combining the numerical and experimental results, the estimated temperature calculated from this model is suitable for control feedback.
Analysis of Coefficient of Thermal Expansion and Thermal Conductivity of Bi-Modal SiC/A356 Composites Fabricated via Powder Metallurgy Route
Authors: Bains Preetkanwal Singh , Payal H. S. , Sidhu Sarabjeet Singh
Published: October 2017

The present study investigates the thermal conductivity and coefficient of thermal expansion of bimodal SiCp reinforced Aluminum matrix composites formed via powder metallurgy method. The after-effects of proportion of particulate reinforcement as size distribution and sintering parameters on the thermal properties have been explored. The Box-Behnken design for response surface methodology was adopted to recognize the significance of chosen variables on the thermal conductivity and coefficient of thermal expansion of the composite. It is witnessed that the thermal conductivity and coefficient of thermal expansion enhanced due to increase in fine SiC particulates volume fraction. It has been exhibited that the fine SiC particulates (37μm) doped Al-matrix occupied interstitial positions and developed continuous SiC-matrix network. SEMs were conducted to evaluate the microstructure architecture for MMCs.
Research and Development of CRAMTRA 1.0 Code for Consequence Assessment From Radioactive Material Transport
Authors: Renze Wang , Jiangang Zhang , Guoqiang Li , Dajie Zhuang , Hongchao Sun , Xuexin Wang , Dongyuan Meng , Shutang Sun
Published: October 2017

Code for consequence assessment (CA) from radioactive material transport (RMT) is an important tool for RMT CA. Since 1980s relevant codes have been introduced from western countries to China, however, there isn’t a code with independent intellectual property rights of China. Design, programming and test of CRAMTRA 1.0 code for RMT CA was introduced in this paper, the results show that CRAMTRA 1.0 has reliable quality and fine practicability.
Fluid Solid Interaction (FSI) Simulation of a Tee Piping in Operating Nuclear Power Plant
Authors: Huang Pei-Hsun , Li Chao-Jen
Published: October 2017

The thermal stress and pressure stress caused by mixing of cold and hot water on a tee junction of piping system in reactor cooling systems of nuclear power plants are the potential place to crack pipe. These stresses are generated due to temperature distribution unevenly in regions where hot and cold flows are intensively mixed together. As operating plants become older and life time extension activities are initiated, operators need screening criteria to exclude risks of pipe cracking. The Kuosheng boiling water reactor (BWR) units 1 and 2, owned by Taiwan Power Company (TPC), started commercial operations in 1981 and 1983, respectively. The purpose of this paper is to assess the Von Mises stresses and deformation of tee piping in Kuosheng’s RHR system by the Fluid Solid Interaction (FSI) simulation. Furthermore, the simulation result compare with the experiment result during the fourth refueling outage per decade in 2014. The temperature and the stress of monitor points established by experiment are all located in the range between maximum and minimum of the experiment result.
Recommendations for Conducting Probabilistic Risk Assessment of Spent Fuel Storage Facilities
Authors: Zhang Sai , Zhao Jun , Tong Jiejuan , Xu Zhixin
Published: October 2017

Currently, the probabilistic risk assessments (PRA) for the nuclear power plant (NPP) sites are primarily focused on the reactor counterpart. However, evoked by the 2011 Fukushima Daiichi accident, it has been widely recognized that a complete site risk profile should not be confined to the reactor units, but should cover all the radiological sources in a site, e.g. spent fuel storage facilities. During the operation of the reactor units, the used fuel assemblies will be unloaded from the reactor core to the storage facilities in a continuous or periodical manner. Accident scenarios involving such facilities can occur with non-negligible frequencies and significant consequences, posing threat to public safety. Hence, the risk contributions from such scenarios should be carefully estimated and integrated into the safety goal evaluations.

The spent fuel storage facilities can be categorized as two types: pool storage units and dry cask storage facilities. In the former type, spent fuel assemblies are stored in large pools inside or outside the reactor building, with the residual heat removed by natural or forced water circulation. The latter type, where air or inert gas circulation plays an important role, appear mostly as a complementary method, along with the pool storage units, to expand the plant’s storage capacity. For instance, at the Daiichi plant, there are several fuel pool units holding some fresh fuel and some used fuel, the latter awaiting for its transfer to the dry cask storage facilities on site. Note that, as well as in a joint manner, both storage facilities can be designed to serve the NPPs independently.

As a fully developed method to identify potential risk in a logical and quantitative way, the framework of PRA can be generally applied to the spent fuel storage facilities with some special considerations. This paper is aimed at giving recommendations for the spent fuel storage facility PRAs, including (1) clarifying the analysis scope of risk from spent fuel storage facilities; (2) illustrating four key issues that determines such risk; (3) presenting three essential considerations when conducting PRAs to evaluate such risk. Also, this paper integrates the insights obtained from two representative case studies involving two NPP sites with different types of both fuel elements and storage facilities.
Influence of Working Pressure and Pressure Difference on Static Droplet Evaporation Characteristics
Authors: Zhao Fulong , Zhao Chenru , Bo Hanliang , Liu Ying
Published: October 2017

The function of steam separator is to remove the small droplets carried by the vapor stream and to provide qualified saturated vapor for the steam turbine in the nuclear power station. The separating characteristics of the steam-water separation plant are of vital importance to the safe operation, economy as well as reliability of the power station. In order to satisfy the requirement of power increase of large nuclear power station as well as space compaction of the vessel power plant, the steam vapor quality must be improved, which requires that the steam-water separator has better separating function to make sure that it can provide the qualified steam on the condition of higher steam pressure, power load as well as circulating ratio. There are many complex phenomena when the droplet moves in the steam-water separating plant, including the droplet emergence, the droplet moving with steam vapor, the collision between droplets and with solid wall, evaporation. It is a good way to study the steam-water separating characteristics for the microcosmic behavior of the droplet. Thus, in order to know the droplet evaporation characteristics in the steam-water separator, the static droplets phase transformation model under the pressure variation condition is built according to the physical phenomenon description and mechanism comprehension when the droplet moves with the steam vapor in the steam-water separation plants. This model is solved by the typical four steps Runge-Kutta method and validated by comparing with the experimental results. Then, the influence of working pressure as well as pressure difference between the droplet surface and the environment on the static droplet evaporation characteristics is conducted. The simulation results show that the working pressure and pressure difference have great impact on the static droplet evaporation characteristics. With the increase of the working pressure, the droplet evaporation rate becomes slower, that is because the physical property parameters of the water vapor and water become closer to each other and the self-diffusion coefficient of the water vapor as well as the evaporation condensation coefficient become smaller, which results in the droplet evaporation rate becomes slower. When the pressure difference between the droplet surface and the environment rises, the droplet evaporates faster, that is because the vapor velocity around the droplet becomes larger and the droplet evaporates faster. These results of the simulation can lay the foundation for subsequent study of the droplet evaporation characteristics when the droplet moving in the separating plants and for the droplet fast evaporation characteristics when the environment pressure changes fast.
Proven Technologies for the Solidification of Complex Liquid Radioactive Waste (LRW): Global Case Studies of Applications and Disposal Options
Authors: Kelley Dennis
Published: October 2017

Legacy radioactive waste streams from the Cold War still exist and newly generated waste streams from nuclear power plants and research institutes go untreated and expose environmental hazards at many nuclear sites. The nature of the waste is extremely diverse, depending upon the source or the process from which it originated. The most problematic waste streams include complex liquids such as organic (tri-butyl-phosphate TBP) solutions contaminated with Pu and U isotopes, mixed sludge types, high acid radioactive waste, H-3 tritium contaminated organic and aqueous streams, etc. Environmental and economic challenges exist for the treatment and disposal of such waste streams.

A proven technology that has been applied to LRW on a global basis provides a low-cost solution to legacy streams and small volume, highly complex LRW frequently generated from routine NPP operations, in nuclear laboratories and during decommissioning. The engineered polymer technology from Nochar, USA, is capable of solidifying standard and highly complex LLW and ILW waste streams for interim or final storage, or for incineration.
Research and Application to Risk-Informed NPP Events Trend Analysis Method
Authors: Shijun Chen , Sifan Zhang , Peifeng Chen , Kuan Zhang
Published: October 2017

The method of the event trend analysis is a so-called analyzed process that will begin with a statistics on a certain characteristic for a set of events over a period of time, and then identify and analyze its variation trend and the reason for its existence so as to develop the corresponding corrective actions. this paper combined with both the traditional event trend analysis and probabilistic safety analysis methods, develops a set of risk-informed trend analysis techniques applicable to the domestic NPPs. This method aims to highlight the significance of the events by placing larger weight on the abnormal incidents of high risk significance, and use the strategy of level management to control the common cause events so that the plant will keep a watchful eye on and give priority to eliminate these events.

In addition, this paper also provides an application case to illustrate the practical use of this method. It is shown that some plants have already obtained several benefits through adopting this method into their event analysis programs. In reality, it will benefit the application of this method into subsequent NPPs event trend analysis process and provide reference and assistance for the safety operation of the nuclear power plants.
Modeling of QUENCH 10 Experiment on Air Ingress Using RELAP/SCDAPSIM Mod 3.5
Authors: Kaliatka Tadas , Uspuras Eugenijus , Allison Chris M.
Published: October 2017

The most important accident management measure to terminate a severe accident transient in a light water reactor is the injection of water to cool the uncovered degraded core. Several experimental and analytical investigations have been made on the subject of zirconium oxidation in the steam and air environment during the last 15 years. The significant group of experiments are the experiments, performed in QUENCH facility. QUENCH-10 experiment was the first experiment from the all QUENCH experiment series with air ingress.

In this article, the RELAP/SCDAPSIM mod 3.5 code version and implemented different oxidation correlations were used to analyze the air ingress experiment QUENCH-10 with the purpose to perform the code and model assessment. The results of analysis will be used in the future computer code improvement and to increase the competence of code users.
Transient Simulation on Reactor Core Melt and Lower Support Plate Ablation in In-Vessel Retention
Authors: Chen Xuyi , Zhang Xiaoying , Xu Junying , Wang Biao , Zhan Dekui , Zhang Huiyong
Published: October 2017

To precisely understand the accident process of reactor core melt in In-vessel retention (IVR) condition, 3-dimensional transient thermal conduction analysis with moving boundary is performed on quarter reactor core model. The decline of decay power and water level in reactor pressure vessel (RPV), and the radial distribution of assemblies of different material is considered. Convective heat transfer on rod surface and coolant interface is computed with empirical correlation of natural convection of saturated steam vapor / water. Radiation heat transfer with 16 neighboring rod is considered. Also, a dynamic ablation model is developed to simulate the ablation of lower support plate (LSP) caused by continuously accumulation of molten corium. The impingement heat transfer of the falling corium and the molten pool formed in LSP ablation cavity is taken into account. The simulation gives the ablation process on the surface of LSP as well as temperature history and molten proportion of the reactor core, which shows agreement with reference. Simulation shows: the melt process of reactor core accelerated in the accident process of 2600s, when coolant in RPV dry up. 65% of the core mass has molten at 8000 second. LSP is completely penetrated in 6000s, the ablation of LSP is mainly focused on an annular region of radius 700mm.
Uncertainty Analysis for the Steady-Stated BEAVRS Benchmark Problem at ARO and ARI Situations
Authors: Wan Chenghui , Cao Liangzhi , Wu Hongchun
Published: October 2017

In this paper, the capability of uncertainty propagations of the nuclear-data to the reactor-physics calculations has been implemented in our home-developed code NECP-UNICORN based on the statistical sampling method (SSM). The “two-step” scheme has been applied in NECP-UNICORN to perform the uncertainty analysis for the reactor-physics calculations. For the lattice calculations, the nuclear-data uncertainties are propagated to the few-group constants; then for the core simulations, the uncertainties of the multiplication factor and power distributions introduced by the few-group constants’ uncertainties can be quantified. Applying the NECP-UNICORN code, uncertainty analysis has been performed to the BEAVRS benchmark problem at the Hot Zero Power (HZP) conditions, with situations of All Rod In (ARI) and All Rod Out (ARO). From the numerical results, it can be observed that for the multiplication factors of the core simulations, the relative uncertainties are about 5.1‰ for the ARO situation and 5.0‰ for the ARI situation, which are the same magnitude of the relative uncertainties of the fuel assemblies; for the radial power distributions, the relative uncertainties can up to be 4.27% as the maximum value and 2.08% as the RMS value for the ARO situation, and 6.03% as the maximum value and 2.37% as the RMS value for the ARI situation.